One Jar To Rule Them All

Giuro per sempre a te, Di viver, morire per te, Se tu sarai con me lo so, Dea Roma, vincerò!

2012-01-31T08:26:00.000+01:00

One of the common problems of people that start using Hibernate is performance, if you don't have much experience in Hibernate you will find how quickly your application becomes slow. If you enable sql traces, you would see how many queries are sent to database that can be avoided with little Hibernate knowledge. In current post I am going to explain how to use Hibernate Query Cache to avoid amount of traffic between your application and database.

Hibernate offers two caching levels:

The first level cache is the session cache. Objects are cached within the current session and they are only alive until the session is closed.
The second level cache exists as long as the session factory is alive. Keep in mind that in case of Hibernate, second level cache is not a tree of objects; object instances are not cached, instead it stores attribute values.

After this brief introduction (so brief I know) about Hibernate cache, let's see what is Query Cache and how is interrelated with second level cache.

Query Cache is responsible for caching the combination of query and values provided as parameters as key, and list of identifiers of objects returned by query execution as values. Note that using Query Cache requires a second level cache too because when query result is get from cache (that is a list of identifiers), Hibernate will load objects using cached identifiers from second level.

To sum up, and as a conceptual schema, given next query: "from Country where population > :number", after first execution, Hibernate caches would contain next fictional values (note that number parameter is set to 1000):

L2 Cache
[
id:1, {name='Spain', population=1000, ....}
id:2, {name='Germany', population=2000,...}
....
]
QueryCache
[{from Country where population > :number, 1000}, {id:2}]

So before start using Query Cache, we need to configure cache of second level.
First of all you must decide what cache provider you are going to use. For this example Ehcache is chosen, but refer to Hibernate documentation for complete list of all supported providers.

To configure second level cache, set next Hibernate properties:

hibernate.cache.provider_class = org.hibernate.cache.EhCacheProvider
hibernate.cache.use_structured_entries = true
hibernate.cache.use_second_level_cache = true

And if you are using annotation approach, annotate cachable entities with:

@Cacheable
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)

See that in this case cache concurrency strategy is NONSTRICT_READ_WRITE, but depending on cache provider, other strategies can be followed like TRANSACTIONAL, READ_ONLY, ... take a look at cache section of Hibernate documentation to chose the one that fits better with your requirements.

And finally add Ehcache dependencies:

<dependency>
<groupId>net.sf.ehcache</groupId>
<artifactId>ehcache-core</artifactId>
<version>2.5.0</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-ehcache</artifactId>
<version>3.6.0.Final</version>
</dependency>

Now second level cache is configured, but not query cache; anyway we are not far from our goal.

Set hibernate.cache.use_query_cache property to true.

And for each cachable query, we must call setCachable method during query creation:

List<Country> list = session.createQuery("from Country where population > 1000").setCacheable(true).list();

To make example more practical I have uploaded a full query cache example with Spring Framework. To see clearly that query cache works I have used one public database hosted in ensembl.org. The Ensembl project produces genome databases for vertebrates and other eukaryotic species, and makes this information freely available online. In this example query to dna table is cached.

First of all Hibernate configuration:

It is a simple Hibernate configuration, using properties previously explained to configure second level cache.

Entity class is an entity that represents a sequence of DNA.

To try query cache, we are going to implement one test where same query is executed multiple times.

We can see that we are returning first fifty dna sequences, and if you execute it, you will see that elapsed time between creation of query and commiting transaction is printed. As you can suppose only first iteration takes about 5 seconds to get all data, but the other ones only milliseconds.

The foreach line just before query iteration will print object identifier through console. If you look carefully none of these identifiers will be repeated during all execution. This fact just goes to show you that Hibernate cache does not save objects but properties values, and the object itself is created each time.

Last note, remember that Hibernate does not cache associations by default.

Now after writing a query, think if it will contain static data and if it will be executed often. If it is the case, query cache is your friend to make Hibernate applications run faster.

Download Code

Music: http://www.youtube.com/watch?v=fw1VJSU92mw

Once upon a time and long ago, I heard someone singing, Soft and low (Distant Melody - Peter Pan)

2012-01-27T11:54:00.001+01:00

Thymeleaf Spring-MVC Maven Archetype aims to create a web application that uses Thymeleaf template engine and Spring Framework.

The main goal of Thymeleaf is to provide an elegant and well-formed way of creating HTML 5 templates. Its Standard and SpringStandard dialects allow you to create powerful natural templates, that can be correctly displayed by browsers and therefore work also as static prototypes.

You can read more about Thymeleaf at:

Thymeleaf: http://www.thymeleaf.org
HTML5 + CSS 3 Form Using Thymeleaf + Spring MVC tutorial: http://www.lordofthejars.com/2011/11/your-big-daddys-got-no-place-to-stay.html

When you create an application using this archetype, generated web application will be composed by two html templates in WEB-INF/views, one for showing a form using HTML5 and CSS3 and another one for listing inserted data.

Spring controllers are located in controller package.

Application is internationalized too using LocaleChangeInterceptor with en_US as default locale. Properties are in src/main/resources/locale folder.

And finally server-side validation is provided by using JSR-303 provider.

Versions of used jars are:

Spring Framework: 3.0.5
Thymeleaf: 1.1.2
Hibernate-Validator: 4.1.0
Slf4j: 1.5.10
Servlet-api: 2.5
JUnit: 4.9

You can install this archetype from source or from jar file:

From source:

mvn clean install

mvn archetype:generate -DarchetypeCatalog=local

From jar:

Download archetype from https://oss.sonatype.org/content/repositories/releases/com/lordofthejars/thymeleafarchetype/thymeleaf-spring-maven-archetype/1.0.0/thymeleaf-spring-maven-archetype-1.0.0.jar

and execute:

mvn install:install-file \ -DgroupId=com.lordofthejars \ -DartifactId=thymeleaf-spring-maven-archetype \

-Dversion=DOWNLOADED_VERSION \ -Dpackaging=jar

-Dfile=PATH_TO_JAR_YOU_DOWNLOADED/thymeleaf-spring-maven-archetype-VERSION.jar

Maven repository is located at

https://oss.sonatype.org/content/repositories/releases/com/lordofthejars/thymeleafarchetype/thymeleaf-spring-maven-archetype

and source code is stored at https://github.com/maggandalf/thymeleaf-spring-maven-archetype

For any question regarding of how to use this archetype or any issue/improvement, do not hesitate to contact me or open a new issue on github.

I wish this archetype can help you to start a new project using Thymeleaf template engine.

Music: http://www.youtube.com/watch?v=7EaGSocm5dc

Nevermind, I'll find someone like you, I wish nothing but the best, for you too, Don't forget me, I beg, I remember you said:-, Sometimes it lasts in love but sometimes it hurts instead (Someone Like You - Adele))

2012-01-23T19:03:00.002+01:00

This week I have reached 100K visits on blog. Simply I would like to say thank you very much to all people that have come and found useful information, my intention is writing posts to make developers life easier.

Especially I would like to thank all dzone folks, theserverside people, springsource bloggers, JavaCodeGeeks, and of course my Twitter followers all of them have helped to reach this number of visits.

To celebrate this event, now alexsotob blog is converted to lordofthejars, so now you can access this blog through alexsotob.blogspot.com or by www.lordofthejars.com.

Thank you very much again to read my blog; my next challenge is to reach 250k visits.

See you next time, keep reading,

Alex.

Music: http://www.youtube.com/watch?v=hLQl3WQQoQ0&ob=av3e

Sábado na balada, A galera começou a dançar, E passou a menina mais linda, Tomei coragem e comecei a falar (Ai se eu te pego - Michel Teló)

2012-01-02T20:44:00.000+01:00

Backbone is a Javascript library that provides a clean way to:

define models in Javascript.
deal with Collections using a rich API.
define Views with declarative event handling and template support.
interface to Rest architectures.

In current post I am going to use the Rest WebApp of my old post, where I only explained the server side to show you how to implement client side using Backbone.

So the first thing to do is create a web structure into IDE, for this example I will reuse same project of RestServer post.

Then download backbone.js and its dependencies and copy to webapp/resources/js directory:

Open servlet-context.xml and add root and js folder as static resource.

Then go to webapp/resources and create index.html.

Add all Javascript libraries into page, but most important, add them in the same order as appears here, if not, some Javascript failures would appear in your browser and the application will not work.

Note that some content is created directly using HTML tags rather than using Backbone views. Normally page layout, headers, footers ... are treated as static content and they are directly written into page.

Let's start modeling our data, in this case a character with its attributes (id, name, url, isHuman...).

Models in Backbone has a particularity that make them useful, they are an implementation of Active Record pattern, so when you are creating a model you will have CRUD operations against a Rest-WebService. So for example when you call save method of your model, Backbone converts that model to JSON and sends the result to server as HTTP POST (if model has no id), or HTTP PUT (update). Other available operations are fetch (load) and destroy (delete).

See how in this case we have created a Character model setting urlRoot property. This property is used to build endpoint to ResetServer. As long as the endpoint returns JSON for a single character, properties will be merged into model.

And the same applies to Collections. When you call fetch method of characters var, all characters returned by calling GET .../characters will be stored into.

See how easy is implementing a Rest Client using Backbone. And I suppose you are wondering where are attributes' definition? Don't worry, with Backbone is not necessary to explicitly define at definition time.

Now it is time for Views. As I cited at the begin of post, Backbone has template support. For this example two templates are going to be used, one for filling a new character and another for showing character information.

To define a template you must use <script> tag with text/template type instead of text/javascript and an id. The structure is similar to JSP (embedded HTML code, <%= %> for printing variables and <% %> for logical structures).

Next step is creating Views.

For this example we are going to create three views, one for each template, and one that will be a composition of both.

Let's start with View responsible of showing information of one character.

At line 3 we are loading template content defined previously with id show-characters, into showCharactersTemplate object.

Next important line is number 6. There we are defining a function that will be invoked each time we want to render a view (one time per character). See how we are passing a model object (trust me it is not defined yet, but will be there), to template. To fill template variables, template engine requires data in JSON format, and Backbone model has a toJSON method. And finally generated html code is saved into el attribute.

Next View is responsible of showing character form, and deal with submit action.

This View shows events handling in Backbone. See line 9. We are defining that when user clicks on tag element "a" with class submit, element defined in new-character template, createOnEnter function is executed.

createOnEnter method does three things:

gets values from template form.
instantiates CharacterModel class. See that this is the place where model attributes are defined.
calls save method. This method sends object data to defined endpoint at server side. Because this operation is asynchronous, a callback is registered, so when a success is received, character is added into characters list.

And last View is a composite view of two previous views, acts as a controller between adding a new character and showing all inserted characters:

Initialize function does all required initializations so UI could be refreshed asynchronously. In first two lines we are binding add and reset functions of characters collection to a method. For example each time add function is called, addCharacter is invoked.

Next line is used to populate data to Collection. When fetch is called an HTTP GET to defined endpoint is sent, data is retrieved and Collection's add method is called for each result.

addCharacter function is responsible of creating one View for each character. There is not much secret, we are creating a CharacterView, and appending the result of calling its render method to html element with character-list id.

And finally render function that is responsible of rendering CharacterFormView.

See that page is only loaded first time we access it, subsequent updates are done by DOM manipulations.

To finish I embedded all html file explained here so you can see a global overview of all pieces used. Also feel free to download all Eclipse project. I wish you find this post useful.

Download Code

Music: http://www.youtube.com/watch?v=q1Ebi9cSn48

Elle ne me quitte pas d'un pas, fidèle comme une ombre. Elle m'a suivi ça et là, aux quatres coins du monde. Non, je ne suis jamais seul avec ma solitude (Ma Solitude - Georges Moustaki)

2011-12-14T21:07:00.002+01:00

In current post I have uploaded my Devoxx presentation. This year I was at Devoxx as speaker. My presentation was about how to speed up HTML 5 applications, and Javascript and CSS in general, using Aggregation and Minification.

Speeding Up JS and CSS Download Times with Aggregation and Minification

View more presentations from Alex Soto.

Also you can visit two entries of my blog where I talk about same theme.

Links of technologies I talked about:

Jawr: http://jawr.java.net/
Wro4j: http://code.google.com/p/wro4j/

Finally I want to say thank you to all people who came to watch me, and of course Devoxx folks, for organising such amazing event.

I wish you have discovered a great way to speed up your web applications.

Music: http://www.youtube.com/watch?v=qSZKO5K2eTE

Far away, long ago, glowing dim as an Ember, Things my heart use to know, things it yearns to remember (Once upon a December - Anastasia)

2011-12-09T20:47:00.001+01:00

You never develop code without version control, why do you develop your database without it? Flyway is database-independent library for tracking, managing and applying database changes.

Personally I find that using a database migration tool like Flyway is "a must", because covers two scenarios of our software life-cycle:

Multiple developers developing an application with continuous integration.
Multiple clients each one with different versions of production code.

Let's start with first point. If your project is big enough there will be more than one developer working on it, each one developing a new feature. Each feature may require a database update (adding a new table, a new constraint, ...), so developer creates a .sql file with all required changes.

After each developer finishes its work, these changes are merged into main branch and integration/acceptance tests are executed on test machine. And the problem is obvious which process updates testing database? And how? QA department executes sql files manually? Or we develop a program that executes these updates automatically? And in what order must be executed? Also same problem arises in production environment.

Second point is only applicable if your application is distributed across multiple clients. And at this point the problem is further accentuated because each client may have different software versions. Hence when an update is required by our client (for example because a bug), you should know which database version was installed and what changes must be applied to get expected database.

Don't worry Flyway comes to rescue you, and will help to fix all previous questions. Let me start explaining some features of Flyway that in my opinion make it a good tool.

Automatic migration: Flyway will update from any version to the latest version of schema. Flyway can be executed as Command-line (can be used with non JVM environments), Ant script, Maven script (to update integration/acceptance test environments) or within application (when application is starting up).
Convention over configuration: Flyway comes with default configuration so no configuration is required to start using.
Plain SQL scripts or Java classes: To execute updates, you can use plain SQL files or Java classes for advanced migrations.
Highly reliable: safe for cluster environments.
Schema clean: Flyway can clean existing schema, so empty installation is produced.

Conventions to be followed if they are not explicitly modified are:

Plain SQL files go to db/migration directory inside src/main/resources structure.
Java classes go to db.migration package.
Files (SQL and Java) must follow next name convention: V<version>[__description]. Where each version number is separated by dots (.) or underscore (_) and if description is provided, two underscores must proceed. A valid example is V_1_1_0__Update.sql

So let's see Flyway in action. In this application I am going to focus only on how to use Flyway, I am not going to create any DAO, DTO or Controller class, only database migration part.

Imagine we are going to develop a small application using Spring Framework that will allow us registering authors and which books they have written.

First version will contain two tables, Author and Book related with one to many relationship.

First step is registering Flyway into Spring Application Context. Flyway class is the main class and requires a javax.sql.DataSource instance. migrate method is responsible to start migration process.

See that there is no secret. Only be careful because if your project uses JPA or ORM frameworks for persistence, you should configure them to avoid auto creation of tables, because now Flyway is responsible of managing database structure. And because of that, creation of SessionFactory (in case of Hibernate) or EntityManagerFactoryBean( in case of JPA), should depends on Flyway bean.

Flyway is configured. Each time you start application, it will review if configured datasource requires an update or not.

And now let's write first version of SQL migration. Create db/migration directory into src/main/resources and create a file called V1__Initial_version.sql with next content:

This script creates Author and Book tables with their respective attributes.

And if you run next JUnit both tables are created into database.

Take a look at your console and next log message has appeared:

10:33:49,512 INFO glecode.flyway.core.migration.DbMigrator: 119 - Current schema version: null
10:33:49,516 INFO glecode.flyway.core.migration.DbMigrator: 206 - Migrating to version 1
10:33:49,577 INFO glecode.flyway.core.migration.DbMigrator: 188 - Successfully applied 1 migration (execution time 00:00.085s).

And if you open your database:

Note that Flyway has created a table to annotate all updates that have been executed (SCHEMA_VERSION) and last insert is a "Flyway insert" marking which is the current version.

Then your first version of application is distributed across the world.

And you can start to develop version 1.1.0 of application. For next release, Address table must be added with a relationship to Author.

As done before, create a new SQL file V1_1_0__AddressTable.sql into db/migration folder.

And run next unit test:

your database will be upgraded to version 1.1.0. Also take a look at log messages and database:

11:27:30,149 INFO glecode.flyway.core.migration.DbMigrator: 119 - Current schema version: 1
11:27:30,152 INFO glecode.flyway.core.migration.DbMigrator: 206 - Migrating to version 1.1.0
11:27:30,191 INFO glecode.flyway.core.migration.DbMigrator: 188 - Successfully applied 1 migration (execution time 00:00.053s).

New table is created, and a new entry into SCHEMA_VERSION table is inserted marking that current database version is 1.1.0.

When your 1.1.0 application is distributed to your clients, Flyway will be the responsible of updating their databases without losing data.

Previously I have mentioned that Flyway also supports Java classes for advanced migrations. Let's see how.

Imagine that in your next release, authors can upload their personal photo, and you decide to store as blob attribute into Author table. The problem resides on already created authors because you should set some data into this attribute. Your marketing department decides that authors inserted prior to this version will contain a photo of Spock,

So now you must alter Author table and moreover update a field with a photo. You can see clearly that for this update you will need something more than a simple SQL file, because you will need to add a new property and updating them with chunk of bytes. This problem could be accomplished using only one Java class but for showing a particularity of Flyway, problem will be treated with one SQL and one Java object.

First of all new SQL script adding a new binary field is created. This new feature will be implemented on version 2.0.0, so script file is named V2_0_0__AddAvatar.sql.

Next step is developing a Java Migration class. Create a new package db.migration on src/main/java. Notice that this class cannot be named V2_0_0_AddAvatar.java because Flyway will try to execute two different migrations with same version, and obviously Flyway will detect a conflict.

To avoid this conflict you can follow many different strategies, but in this case we are going to add a letter as version suffix, so class will be named V2_0_0_A__AddAvatar.java instead of V2_0_0__AddAvatar.java.

Before run previous unit test, open testdb.script file and add next line just under SET SCHEMA PUBLIC command.

INSERT INTO AUTHOR(ID, FIRSTNAME, LASTNAME, BIRTHDATE) VALUES(1, 'Alex', 'Soto', null);

And running unit test, next lines are logged:

20:21:18,032 INFO glecode.flyway.core.migration.DbMigrator: 119 - Current schema version: 1.1.0
20:21:18,035 INFO glecode.flyway.core.migration.DbMigrator: 206 - Migrating to version 2.0.0
20:21:18,088 INFO glecode.flyway.core.migration.DbMigrator: 206 - Migrating to version 2.0.0.A
20:21:18,114 INFO glecode.flyway.core.migration.DbMigrator: 190 - Successfully applied 2 migrations (execution time 00:00.094s).

And if you open updated database, next lines are added:

See how all previous authors have avatar column with data.

Note that now you have not to worry about database migrations, your application is packaged and delivered to all your clients regardless of the version they had installed; Flyway will execute only required migration files depending on installed version.

If you are not using Spring, you can update your database using Flyway-Maven-Plugin. Next piece of pom shows you how to execute migration during test-compile phase. By default plugin is executed during pre-integration-test phase.

Thanks of Maven plugin, we can configure our continuous integration system so all environments (test, production,...) would be updated during deployment of application.

I wish Flyway will help you make better life as developer.

Download Code

Music: http://www.youtube.com/watch?v=oyUBdLm3s9U

All my scientists are working on a deadline, So my psychologist is working day and nighttime, They say they know what's best for me, But they don't know what they're doing (Atomic Garden - Bad Religion)

2011-12-01T19:55:00.001+01:00

Maven archetypes are project templates that allow users create project structure with a simple Maven command. In my company we are using archetypes because provide a way to standardize projects structure. All our projects are built using the same directory structure, all of us use the same version of common libraries like JUnit, Hamcrest, Spring Framework, Mockito, or in case of web applications bundling them with company's approved CSS and Javascript libraries. Also PMD, checkstyle or findbugs coding rules can be stored in distributed archetype.

If each time you start a new project you are of those who copy files from existing projects to the new one, apply DRY principle and create a Maven archetype from existing project.

First thing to do is create your template project with all files to be bundled into archetype. In this example, simple Spring MVC project will be transformed to be a Maven archetype.

After template project is created and all desired files are added, you should have a directory layout like:

My personal advice is that if you are thinking about distributing this archetype with community (not only for your company), remove all IDE specific files.

Now you have your project created and ready to be packaged as archetype. Execute next command on root of your project.

mvn archetype:create-from-project

And Maven console output should be:

And now your archetype is created in target/generated-sources/archetype directory with next hierarchy:

Now project is inside archetype-resources directory. This directory contains all files that will be added in generated project.

At first sight, not much differences between original project and "template" project, it seems that only three files has been added archetype-metadata.xml, archetype.properties and goal.txt, but shortly you will see that original project content has been modified too.

Before continuing see that in project exists two poms, one pom that is in root directory, that will be called archetype pom, because it contains all archetype configuration, and another one into archetype-resources, called template pom, because it will be the pom used in generated project.

Next step is isolate archetype project into separate folder, so can be dealt as alone project.

mv target/generated-sources/archetype ../spring-mvc-archetype

Following step is adding a name to generated archetype, so open archetype pom and change <name> tag value to your archetype name, for example spring-mvc-archetype, and if you want artifactId and groupId too.

After this modification, open archetype-resources' pom, and see how <artifactId> or <groupId> values are surrounded with ${artifactId} or ${groupId}. When you are creating a new archetype, by default Maven will ask you to enter four parameters, groupId, artifactId, version and package. Entered values will be used to fill placeholders.

With default four parameters should be enough, but imagine you want that user provides more information, for example, war name. To get this, open archetype-metadata.xml file (src/main/resources/META-INF/maven) and add one required property, using <requiredProperties> tag.

In previous file we are adding a new required property named warName. And last thing to do is update
archetype.properties located on test/resources/projects/basic with default value of new property.

And that's all, if you open any Java class or any Xml file, you will see that has been modified with ${package} variable. This information is filled when you generate the project.

Now you can install archetype into your local catalog and start generating standardized projects.

mvn clean install

And your artifact is ready to be used. Try next command or if you have installed m2Eclipse plugin open Eclipse and try your new archetype:

mvn archetype:generate -DarchetypeCatalog=local

A list of all installed archetypes is shown. Choose previously created and fill up all required properties, and your new project is built and configured. You can start coding with same libraries that your workmates use and same style rules.

In this post a simple example has been provided, but think about all kind of elements that you copy and paste from one project to another like SCM connection, surefire plugin configuration, release plugin tag name, to cite a few, and how you can integrate them into your archetype.

I wish you have found this post interesting.

Music: http://www.youtube.com/watch?v=AhzhiQA6-Aw&ob=av3e

Your big daddy's got no place to stay, Bad communication, I feel like the president of the USA (Mr. Bad Guy - Freddie Mercury)

2011-11-25T18:40:00.001+01:00

In current post I am going to explain how to implement nice web form using HTML 5 and CSS 3 effects, and how can be integrated into Spring MVC web application.

First thing to do is create a Spring MVC skeleton project using STS Spring Templates. In fact you can use any other method but I prefer to use a standard template.

Next step is create an HTML 5 web structure, but exists some online applications that can do this for you, hence I am going to HTML 5 Boilerplate site, and create a custom HTML 5 template.

Then open downloaded zip and copy required structure into previous generated project. Css and Js folders into resources directory, and rename index.html to index.jsp and copy it to views directory.

Now open servlet-context and add mvc:resources tag for serving static resources.

If you deploy application a white screen should be showed but without any client/server error.

Let's start creating next html form.

Now open index.jsp and remove div with id main and create next form:

And now if you run again, you should see something like:

Add @import url(http://fonts.googleapis.com/css?family=Yanone+Kaffeesatz); on top of CSS file.This will make a nice font available from Google Fonts directory.

Now it is time to start applying CSS for creating a better layout. Open style.css and modify/create next elements:

And now your form should look with next layout:

See that new font is not used, simply find body,button,input,select,textarea entry and remove font-family property.

Better than before, see how only modifying CSS, form layout is modified.

And now let's start with CSS3 magic.

First trick is adding shadows and gradients to form.

And next lines into input, textarea style:

where -moz prefix is used for Gecko based browsers, and -webkit is used for Webkit browsers.

Next lines add some mouse over effects into form elements.

And to finish applying styles, we are going to modify submit button.

Remove input[type="submit"] from button and input style.

And add next lines into CSS file:

CSS magic is over, now it is time to start with server side.

If you look careful Spring taglibs, you will see that you cannot create for example email input types directly or URL types to cite a few. So I decided to use a new template engine called Thymeleaf, that offers a really nice approach for integrating HTML 5 with Spring MVC applications.

The main goal of Thymeleaf is to provide an elegant and well-formed way of creating HTML 5 templates. Its Standard and SpringStandard dialects allow you to create powerful natural templates, that can be correctly displayed by browsers and therefore work also as static prototypes. This is possible due the absence of taglibs like <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>.

First thing to do is change index.jsp to index.html, and change ViewResolver to Thymeleaf ViewResolver:

First add Thymeleaf dependencies into pom and then modify servlet-context.xml to register TempateResolver, TemplateEngine and ThymeleafViewResolver and remove the deault view resolver.

Next step is modeling our form to a model class, and modify Spring Controller to manage form submition.

Model class is not shown because is a simple POJO with form fields. Let's see how controller is modified.

Open HomeController class and create two methods (GET, POST) to deal with HTML5 form. Note that it is a typical Spring Form Controller;

And finally we are going to templarize index.html content, using Thymeleaf engine.

Open index.html and make next changes:

Add Thymeleaf namespace on html tag.

<html xmlns:th="http://www.thymeleaf.org">

Then change form tag with two new attributes, one with object's model name (form backing object) and other one with submition URL.

<form action="#" th:object="${messageInfo}" th:action="@{/}" method="post">

Next thing to do is change each form element with th:value attribute containing backing object property name.

<input type="text" name="name" value="" id="name" placeholder="Your Name" required="required" autofocus="autofocus" th:value="*{name}"/>

And more few changes should be performed:

Use DOCTYPE instead of doctype

At time of writing this post, html5boilporate introduces link tag without closing, so Thymeleaf parser will throw an exception if is executed as is, so let's terminate link tag and meta tags.

And finally last change is required because of xhtml correctness:

<script> tag is surrounded with CDATA tags. See explanation here: http://javascript.about.com/library/blxhtml.htm.

Now you can deploy application and your HTML5+CSS3 form is displayed and data submitted is displayed through server console and form page is reloaded with introduced data. And now I am going to explain what are those strange expressions in form and then we will add a new page.

Inside each Thymelef attribute four kind of expressions can be used:

${...} are Spring EL expressions and are executed on model attributes.
*{...} are expressions executed on the form backing bean, it is like a pointer to form object (root).
#{...} are for internationalization.
@{...} are link expressions to rewrite URLs.

And before jumping to next section try this, instead of opening index.html from http://localhost:..... try to open from your drive file://.... and I suppose you see that that's not a nice prototype because no styling is applied. This happens because we are using CSS location as:

<link rel="stylesheet" href="css/style.css"/>

HTML file is at /src/main/webapp/WEB-INF/views/ and this directory does not contain css folder. And now you can think that I have not told you the true about prototyping with Thymeleaf, but wait trust me and change that line to:

<link rel="stylesheet" href="../../css/style.css" th:href="@{/css/style.css}"/>

And open again, and wow now you can see it, a real page as one generated by the server. What we have changed is that when a browser opens HTML file without using template engine (offline), href attribute is used, but when page is online (and requested file acts as a template), th:href attribute is used.

Listing Messages:

Let's start creating a new HTML file to display all inserted messages and apply some styling with CSS.

First add a new CSS property to apply same design in table.

New CSS 3 property (nth-child) is used so even tr tags of a table will contain different style than odd tr tags.

Then create a file called list.html in same level of index.html:

This is a copy paste of index.html but changing div with id content.

In this case we are using another nice feature of Thymeleaf, collection iteration. With th:each you are iterating over a collection of elements. See that rowStat variable can be used for retrieving column information like number of column. And also see how we are defining default values between td tags, so this file is a prototype too.

Next step is changing our controller, so homeForm (renamed to showResults) method returns a list of messages:

Using a simple list as repository is not a good design, but for teaching purpose is enough. See that view name is set to list, and list of messageForm are sent back with model name used in th:each attribute.

Internationalization:

Next step is internationalizing the application. For this reason we create a message properties file (messages_en_US.properties) into src/main/resources/locale:

Then you must configure Locale beans in Spring context file.

And finally change index.html and list.html static values to internationalized keys using #{} expression:

<th th:text="#{theader.count}"></th>
<label for="name" th:text="#{theader.name}">Name: </label>

And although internationalization is used, web page is still a prototype.

It seems like application is working well, but it has one problem. Try next sequence of events:

1. Add a new message.
2. When list of all messages are shown, refresh the page (F5).

And surprise the same message is added too, so now we have two repeated messages, but you have only inserted one.

To fix this problem we must change our controller and use redirect keyword on create method to redirect to a method of controller that finds all inserted messages.

When a new message is created (create method), a redirect to /list is returned, then showResults method is called, and returns a list with all inserted messages. Remember to change th:action from form tag to /insert too.

And now if you execute the same process as before, no multiple insertions occur.

Validation:

And as final step let's see how to implement validation with Thymeleaf.

First thing is adding Jsr-303 provider into our pom. In this case Hibernate-Validator.

Next step is changing our model by for example creating a length constraint in phone field:

@Length(min=9)
private String phone;

To trigger validation of a @Controller input, you must annotate input arguments with @Valid. So our controller is modified to:

And finally modify form page so when an error occurs, a message is shown.

First a new CSS style is created for showing error message:

See that in previous style we are defining an img folder so new static resource resolution in servlet-context.xml as done with css and js folders must be registered.

And finally in index.html a new div is created for showing errors:

For showing errors, #fields variable is used. This variable is provided by Thymeleaf and contains all errors bound by Validation Framework. Note that star '*' is used as errors function parameters for returning all errors produced by all form fields, but Thymeleaf allows you to specify only one particular field.

Conclusions:

From this post I have learned some interesting points:

With new HTML5 tags, some Javascript validation (like entering well-formatted email) is not required anymore.
CSS 3 shadows and gradients properties allow us to create amazing forms without using complicated structures of images.
Thymeleaf is an amazing template engine, in fact for me a real way for creating prototypes and final code at once.
Thymeleaf is a young project, and for example does not support jQuery by default, but exists a Thymeleaf dialect that integrate it. I think that in nearest future it will be a template engine to be consider.

Hope you find Thymeleaf useful too.

Download Code.

Music: http://www.youtube.com/watch?v=MMr1zH8NoEY

What a wicked game you play, To make me feel this way, What a wicked thing to do, To let me dream of you ( Wicked Game - Chris Isaak)

2011-11-18T16:17:00.001+01:00

In my previous post I was talking about how to create a service using Jdk service provider. In current post I am going to talk about how to implement your own Jsr223 Script Engine. And as you will see, script engines are a kind of Jdk service providers, so instead of creating your own set of interfaces, we are going to see how to implement a service provider of an already defined service.

Moreover we are going to see how we can convert a scripting language expression evaluator (in this case Spring EL) to be Jsr-223 compliant.

First of all for those who do not know what is Jsr-223 specification (or Java Scripting API), Jsr-223 is a scripting language independent framework for using script engines from Java code. Thanks of Jsr-223, we only use javax.script package instead of importing language specific classes.

For example using Spring EL scripting language, requires you import in your business class at least two Spring classes ExpressionParser and SpelExpressionParser, and if you want to use another scripting language, more specific vendor classes should be added, so your code is tied to script parser used.

If you use Java Scripting API, two classes are required, ScriptEngineFactory and ScriptEngine, regardless of the language used. And this occurs because ScriptEngine is an interface returned by ScriptEngineFactory service.

Let's start coding:

First class to implement is ScriptEngineFactory and is responsible of creating a new ScriptEngine. It must implement ScriptEngineFactory interface and its implementation will be the service provider of Scripting API.

First part of class is where we are defining what is the name of script language used to get the engine, the version of language (I have chosen Spring version), and version of engine.

Then three special methods:

getMethodCallSyntax: returns a String which can be used to invoke a method of a Java object using the syntax of the supported scripting language. In case spEL, the equivalent of calling a Java method from script, is using Types with special T operator.
getOutputStream: returns a String that can be used as a statement to display the specified String using the syntax of the supported scripting language. In case of spEL, there is no output stream so an unsupported exception is thrown.
getProgram: returns a valid scripting language executable progam with given statements. As previous method, an unsupported exception is thrown.

and finally the most important method getScriptEngine, which must return an implementation of ScriptEngine interface. In this case the Spring EL script engine. Let's see how spEL ScriptEngine is implemented.

First of all class extends from AbstractScriptEngine, which provides implementation for several of the variants of the eval method. Compilable interface is implemented too. ScriptEngines that implements this interface can compile scripts so any further execution of expression does not require any recompilation.

Most important method is eval which should cause immediate script execution using vendor library.

Main purpose of this class is adapt Jsr-223 classes to Spring EL classes. If you look carefully this class, it contains a private inner class that extends CompiledScript. This class is responsible of storing compiled expression, so subsequent calls of eval method requires no reparsing. This class is returned when compile method is called.

As final note spEL language contains some features that go beyond a standard script like registering Java functions into script, referencing Spring Beans, expression templating or navigation through properties of root objects. Of all of these features I think it would be useful having root objects support in Jsr-223 implementation, so I have coded a special attribute named "root". So if you set an attribute to script context with name "root", attribute's content will be treated as root object.

Before implementing this solution I wondered another possibilities like not implementing root objects, or using Adapter pattern implementing two interfaces ScriptContext and EvaluationContext, but I dismissed because there were duplicated methods (different signature, same behaviour), and from developer's point of view could be a bit confusing. Moreover this approach implies that caller should know that are running spEL script. Also I planned of using MethodResolver or PropertyResolver but was rejected because spEL would have been extended.

With attribute approach, if you are not using root objects, there are no differences between using Scripting API with Javascript, Groovy or spEL.

And finally service configuration. Create META-INF/services directory into resources folder, and create javax.script.ScriptEngineFactory file; this is the full qualified name of service interface with next content:

And that's all about implementation, with next unit tests you will see clearly how is used:

First one is testing that SpelScriptEngine is returned by ScriptEngineManager.

Not complicated, it is used as you would use for retrieving Javascript engine. Short name is used as engine identifier.

And next unit test contains some assertions about how some Spring EL features are used with ScriptEngine rather than SpelExpressionParser.

Notice how in first test, SpelScriptEngineImpl.ROOT_OBJECT constant is used, so Inventor instance is specified as root object.

Hope you found this post useful.

Feel free to use this code, I have created a git repository so you can download, branch, ... https://github.com/maggandalf/spEL223

Also I have uploaded project as zip file. Download Code.

Music: http://www.youtube.com/watch?v=UAOxCqSxRD0

Fear of the dark, fear of the dark I have a phobia that someone's always there (Fear of the Dark - Iron Maiden)

2011-11-10T20:26:00.000+01:00

Some time ago I wrote about how to implement your Restful Web API using Spring MVC. Read my previous post to know about it.

In that post it was developed a simple Rest example. For testing the application, file was copied into a web server (Tomcat for example), and then accessing to http://localhost:8080/RestServer/characters/1 information of character 1 was returned.

In current post I am going to explain how to transform that application to a Google App Engine and be deployed into Google's infrastructure using Maven. Of course in this case we are going to deploy a Rest Spring MVC application, but same approach can be used for migrating a Spring MVC web application (or any other application developed with other web framework) to GAE.

First of all, obviously you should create a Google Account and register a new application (remember the name because will be used in next step). After that you can start the migration.

Three changes are required, create appengine-web.xml defining application name; add server tag to settings.xml with Google account information, and modify pom.xml for adding GAE plugin and its dependencies.

Let's start with appengine-web.xml. This file is used by GAE to configure application and is created into WEB-INF directory (at same level of web.xml).

The most important field is application tag. This tag contains the name of our application (defined when you register a new Google Application).

Other tags are version, system properties and environment variables, and misc configuration like if you want a precompilation to enhance performance or if your application requires sessions.

And your project should not be modified anymore, now only Maven files will be touched.

In settings.xml, account information should be added:

See that it is as easy as registering any other server in Maven.

And finally the most tedious part, modifying pom.xml.

First thing is adding new properties:

At first line we are defining Appengine Java SDK location. If you have already installed then insert location in this tag, if not, copy same location of this pom and simply change maven repository directory, in my case /media/share/maven_repo, to yours. Typically your Maven repository location will be /home/user/.m2/repositories. Maven will download SDK for you at deploy time.

Next step is adding Maven GAE repository.

Because our project is dummy project, Datanucleus are not used. In case of more complex projects, that database access is required using, for example JDO, next dependencies should be added:

And in case you are using Datanucleus, maven-datanucleus-plugin should be registered. Take care to configure it properly depending on your project.

Now Google App Engine dependencies are added.

Then if you want to test GAE functionalities (not used in our dummy project), next GAE libraries are added:

Next change is a modification on maven-war-plugin including appengine-web.xml into generated package:

And finally adding maven-gae-plugin and configuring it to upload application to appspot.

See that <serviceId> tag contains the server name defined previously in settings.xml file.

Also if you are using maven-release-plugin you can upload application to the appspot automatically, during release:perform goal:

Now run gae:deploy goal. If you have already installed Appengine Java SDK, then your application will be uploaded to your GAE site. But if it is the first time you run the plugin, you will receive an error. Do not panic, this error occurs because Maven plugin does not find Appengine SDK into directory you specified in <gae.home> tag. But if you have configured gae.home location into your local Maven repository, simply run gae:unpack goal, and SDK will be installed correctly so when you rerun gae:deploy your application will be uploaded into Google infrastructure.

In post example you can go to http://alexsotoblog.appspot.com/characters/1 and character information in JSON format is displayed into your browser.

As I have noted at the beginning of the post, the same process can be used for any web application, not only for Spring Rest MVC.

Because of teaching purpose all modifications have been made into application pom. My advice is that you create a parent pom with GAE related tags, so each project that must be uploaded into Google App Engine extends from same pom file.

I wish you have found this post useful.

This week I am at devoxx, meet me there ;) I will be speaking on Thursday 17 at 13:00 about Speeding Up Javascript & CSS Download Times With Aggregation and Minification.

Full pom file:

Download Code.

Music: http://www.youtube.com/watch?v=Nba3Tr_GLZU

I en una paret al fons imprès en blanc i negre hi havia un pòster d'en Godard. Potser ell em podria dir-me perquè em ballava el cap. (Jean Luc - Els Amics de les Arts)

2011-11-07T09:27:00.000+01:00

Although you can think that Comma-Separated Values (CSV) files are simple files where each value is separated by commas, it is far from reality. The most important part of CSV files are delimiters, and one can think that the delimiter, as type name suggests, is comma. But this assumption is not always true and CSV is often applied to files using other delimiters. Typical example is found in countries where comma (,) is used as decimal separator, because you would have no way to discern between decimal number or separator, semicolon (;) is used.

If your application is distributed across different countries and your application should support Comma-Separated Values files, then you should take care about this important fact.

Let's see how can we resolve this problem so we can read CSV files depending on country.

For reading CSV files we are going to use openCSV library. This API contains one class for reading CSV files (CsvReader) and another for writing (CsvWriter). By default it uses comma as column delimiter, but you can also inform which delimiter character must be used.

So the problem is how to know which delimiter we should use. And for resolving this problem we can use DecimalFormatSymbols class. This class represents the set of symbols needed to format numbers.

DecimalFormatSymbols has a method called getDecimalSeparator() that as his name suggests returns a decimal symbol, comma (,) in case of countries like Germany, and dot (.) in case US for example. So with a simple ternary you could know which delimiter is used in CSV files depending on locale.

So final class will look like:

And previous factory can be instantiated with Spring and injecting delimiter, using Spring Expression module.

See that thanks of Spring Expression delimiter is injected directly into class.

I think it is not difficult to implement an application that can read Localized Comma-Separated Values files, and can avoid having problems when application is distributed around the world.

Full Code: https://github.com/downloads/maggandalf/Blog-Examples/csv.zip

Music: http://www.youtube.com/watch?v=A3Yl3Fsj7tw&feature=related

En ti puedo ver la libertad, Tu me haces sentir que puedo volar, Y se que aquí es mi lugar, Y se que a ti yo quiero amar (Cuando Me Miras Asi - Cristian Castro)

2011-11-02T08:43:00.006+01:00

From ServiceLoader javadoc: A service is a well-known set of interfaces and classes. A service provider is a specific implementation of a service. The classes in a provider typically implement the interfaces and subclass the classes defined in the service itself.

Since JDK 6, a simple service-provider loading facility is implemented. As is suggested it is simple, you cannot understand that implementation as a complex system for implementing plugins for your application, but can help you in many situations where you want implementations of a service could be discovered by other module automatically.

What I really like about using JDK Services is that your services do not have any dependency to any class. Moreover for registering a new implementation of a service, you just have to put jar file into classpath and nothing more.

Now I will explain the service we are going to implement, and then I will show you how to code it.

We want to implement a system that depending on kind of structured input (comma-separated value, tab-separated value, ...) returns a String[] of each value; so for example you can receive input a,b,c,d or 1<tab>2<tab>3<tab>4 and the system should return an array with [a, b, c, d] or [1, 2, 3, 4].

So our system will have three Java projects.

One defining service contract (an interface) and, because of teaching purpose, a main class where internet media type, for example text/csv, is received with input data. Then using a factory class that I have created, it will ask which registered service can transform input to String[].

And two projects each one implementing a service following defined contract, one for comma-separated values and another one for tab-separated values.

Let's see the code:

Main project (reader) is composed by an interface, a main class and a factory class.

The most important part is Decode interface which defines service contract.

Two operations are defined, one that returns if service supports given input, and another that transforms data to String[].

DecodeFactory class is responsible for finding an implementation service that supports required encoding. In fact, this class encapsulates java.util.ServiceLoader calls. ServiceLoader class is in charge of load registered services.

At line 3 we are loading all services that are registered in classpath. At line 7 we only iterate through all services asking if given encoding name is supported.

And finally main class.

And now if you run this class with java -jar reader.jar "text/cvs" "a, b, c, d", an UnsupportedEncodingException will be thrown. Now we are going to implement our first service. Note that reader project will not be modified nor recompiled.

First service we are going to implement is one that can support comma-separated values encoding. Only one class and one file are important.

CSV class is an implementation of Decode interface and transforms comma-separated values.

As you can see a simple StringTokenizer class. Only take care that this class is Locale sensitive, countries where comma (,) is used as decimal delimiter, separation character is semicolon (;).

And next important file is a file that is placed into META-INF. This file contains a pointer to service implementation class.

This file should be in META-INF/services and should be called as interface full qualified name. In this case org.alexsotob.reader.Decode. And its content should be service implementation full qualified name.

And now you can package this project, and you can reexecute reader project but with generated jar (csv.jar) into classpath. And now output will be an array with a, b, c and d characters instead of unsupported exception.

See that reader project has not been modified and its behaviour has been changed. Now you can develop new implementations for decoding new inputs, and you should only take care of copying them into classpath.

Only take care that all services should have a default constructor with no arguments.

And for those who use Spring Framework, Services are also supported through three different FactoryBeans, ServiceFactoryBean, ServiceListFactoryBean, ServiceLoaderFactoryBean.

As I have noted at start of this post, JDK services is a simple (yet powerful) solution if you need to create a simple plugins system. In my case it has been enough with JDK services, and I have never required more complex structure; but in case you are thinking about a complete plugin solution you can use JPF that offers a solution like Eclipse plugins, or even OSGI.

I wish you have found this post useful and now you know (if you didn't know yet), an easy solution to develop modules that are plugged and play.

Download Main Project: https://github.com/downloads/maggandalf/Blog-Examples/reader.zip
Download Comma-Separated Values Service Project: https://github.com/downloads/maggandalf/Blog-Examples/csvDec.zip
Download Tab-Separated Values Service Project: https://github.com/downloads/maggandalf/Blog-Examples/tsvDec.zip

Music: http://www.youtube.com/watch?v=5cV_sIdpXeA&feature=related

Soy el rey de la mar tiburón Que te come a besos Pero yo soy el rey del mar tiburón El que te come mi amor (El Rey Tiburón - Maná))

2011-10-25T08:11:00.001+02:00

Today I was googling about mocking when I have found next question:

"Injecting mock beans into spring context for testing. What I want to be able to do is via the HotswappableTargetSource override the bean definitions of select beans in my application context with my test versions and then run the test.
Then for each test case I'd like to specify which beans I want to be hot swappable and then each test must be able to create its own mock versions and swap those in, and be able to swap back again."

And there you can find a solution using ProxyFactoryBean and HotSwappableTargetSource. Well it is a solution for me a bit complicated, if I should do the same I would do using StaticApplicationContext class, because from my point of view, environment is more controlled and easy to understand. Of course the easiest solution is using Spring 3.1 Profile feature, but meanwhile it is a milestone/RC or simply because you will not be able to change Spring version, I will show you how to use StaticApplicationContext and how to inject mocked beans.

StaticApplicationContext is an implementation of ApplicationContext interface which supports programmatic registration of beans and messages, rather than reading bean definitions from external configuration sources. StaticApplicationContext has been created mainly for testing purpose. To solve the problem we focus, some of registered beans will be the "real" beans, but others will be mocked beans with all their interactions.

For this example Mockito has been used. Let's see some code.

Imagine you have an application that should create users into a database. I suppose we would have a UserDao class for communicating with database and a UserService class to aggregate user operations. Moreover UserService class would not be alone, would be used in several modules; in fact all modules that requires user information.

Now it is time for testing. Unit test is simple, when you want to test UserService you set a mock of UserDao. Here no problem with Spring because it has not started to play yet.

But when you want to test whole system, may be you want that low-level classes like UserDao be mocked and also you want to run tests with Spring capabilities (for example developed BeanPostProcessors, Messaging, Spring AOP, ...). For solving this case you can create a test Spring context file, then you can create required mocks and set them manually. But as you can suppose another approach is using StaticApplicationContext.

The most important line is number 12 where we are injecting UserDao mock into Spring context. See that at line 11 we are also registering autowired annotation post processor. If it was not registered, classes annotated with @Autowired would not work.

In current post I have explained how to inject mock beans into Spring Context for testing. Personally I don't like mixing mock beans with real beans in integration tests, I prefer only real beans in this kind of tests; but I can understand that in big modules where a system has multiple subsystems can be useful to isolate some modules from test.

For example in my department we are developing clinical instruments which as you can imagine contains complex modules all related between them. When we are running some integration test, we are not available to connect to device, so communication module could be mocked. But in our case we are running integration tests with an emulator, but mocking some parts of our system could be another solution.

The example in this case is so simple I know, but in more complex scenarios you can create an application context referencing to real beans and passing it to StaticApplicationContext constructor so in static application context you only register mock beans.

This this would look:

Well now I have showed you how to register mock beans into a Spring Application Context using StaticApplicationContext instead of using HotSwappableTargetSource.

Thank you very much for reading my blog.

Download Code.

Music: http://www.youtube.com/watch?v=Njbm_MABQJE&ob=av2n

Una terra promessa Un mondo diverso Dove crescere i nostri pensieri Noi non ci fermeremo Non ci stancheremo di cercare Il nostro camino (Terra Promessa - Eros Ramazzotti)

2011-10-17T14:22:00.000+02:00

INTRODUCTION

The essence of the Observer Pattern is to "Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically." GoF. Observer pattern is a subset of publish/subscribe pattern which allows a number of observer objects to see an event.

This pattern can be used in different situations, but in summary we can say that Observer pattern can be applied when an object should be able to notify messages to other objects, and you don't want these objects being tightly coupled. In my case I have used this pattern when an asynchronous event should be notified to one or more graphical component.

This pattern can be implemented using an adhoc solution or using java.util.Observer/Observable classes. But my projects are always developed with Spring whether they are web or desktop applications. So in current post I will explain how I implement Observer pattern with Spring.

HANDS ON

Event handling in Spring ApplicationContext is provided through ApplicationEvent class and ApplicationListener interface. If a bean that implements ApplicationListener interface is deployed into the context, every time an ApplicationEvent is published to container, ApplicationListener receives it.

Spring comes with built-in events, like ContextStartedEvent, ContextStoppedEvent, but you can also create your own custom events.

For developing your own events, three classes are required, observer role, observable role and the event. Observers are those who receive events and must implement ApplicationListener class. Observable classes are responsible of publishing events and must implement ApplicationEventPublisherAware. Finally event class has to extend ApplicationEvent.

CODING

What I am going to implement is wikipedia example of Observer pattern (http://en.wikipedia.org/wiki/Observer_pattern#Example) but using Spring Events instead of Observer/Observable Java classes. The example is a basic publish/subscribe example where one String message is sent from one module to another one.

Let's create MessageEvent. This event contains a String that represents the message we want to send. It is a simple class that extends from ApplicationEvent.

Next class is the Observable class. This class must implements ApplicationEventPublisherAware. This interface defines a setter method with ApplicationEventPublisher as parameter. This parameter is used for publishing events.

In current implementation see that also implements Runnable interface so user can create from console input, asynchronous messages. Most important line is 26 where an event is created and published.

The Observer class is even simpler. Implements ApplicationListener interface. Method onApplicationEvent is called when an event is published. See that it is a generic interface, so no cast is required. This differs from java.util.Observer class.

In application context file, you register both ApplicationListener and ApplicationEventPublisherAware beans.

And finally a main class to test the system. A thread is created to execute multiple asynchronous events.

So start the program and write something to console. You will see something like:

hello

Thread-0

MessageEvent [message=hello]

I have entered "hello" message and thread name of event publisher is printed. Then event is sent and handler thread name is printed too. Finally the received event is shown. There is one thing that should call your attention. Both sender (Observable) and receiver (Observer) are executed in same thread; by default event listeners receive events synchronously. This means that publishEvent() method, blocks until all listeners have finished processing the event. This approach has many advantages (for example reusing transaction contexts, ...), but in some cases you will prefer that each event is executed in new thread, Spring also supports this strategy.

In Spring, class responsible of managing events is SimpleApplicationEventMulticaster. This class multicasts all events to all registered listeners, leaving it up to the listeners to ignore events that they are not interested in. Default behaviour is that all listeners are invoked in calling thread.

Now I am going to explain how Spring Event Architecture is initialized and how you can modify. By default when ApplicationContext is started up, it calls initApplicationEventMulticaster method. This method verify if exists a bean with id applicationEventMulticaster of type ApplicationEventMulticaster. If it is the case defined ApplicationEventMulticaster is used, if not a new SimpleApplicationEventMulticaster with default configuration is created.

SimpleApplicationEventMulticaster has a setTaskExecutor which can be used for specifying which java.util.concurrent.Executor will execute events. So if you want that each event is executed in a different thread, a good approach would be using a ThreadPoolExecutor. As explained in last paragraph, now we must explicitly define SimpleApplicationEventMulticaster instead of using default ones. Let's implement:

First of all SimpleApplicationEventMulticaster must be defined as a bean with id applicationEventMulticaster. Then task pool is set, and we rerun our main class. And output will be:

hello

Thread-1

pool-1

MessageEvent [message=hello]

Note that now sender and receiver thread is different.

And of course you can create your own ApplicationEventMulticaster for more complex operations. You just have to implement ApplicationEventMulticaster and defining it with applicationEventMulticaster bean name, and events will be executed depending on your own strategy.

Hope that now your Spring desktop applications can take full advantage of Spring events for separating modules.

Download Code.

Music: http://www.youtube.com/watch?v=GfnkcKiocRw

You're so sexy sex sex sexy. Feel me now and stop the conversation. No, no, no don't stop the desire no, No, no, no, no! (Sexy - French Affair)

2011-10-11T08:24:00.001+02:00

INTRODUCTION

In current post I am going to explain how to implement and register a custom Spring MVC HttpMessageConverter object. Specifically a converter that binds objects to Yaml protocol. As starting point I am going to use the Rest application I implemented in previous post. That application is a simple Restful application where XML and JSON (Spring MVC already support them) are used. Because Spring MVC does not implement YamlMessageConverter, I am going to explain how to transform previous application from supporting XML and JSON to support Yaml.

Yaml is a human-readable data serialization format that takes concepts from programming languages such as C, Perl, and Python, and ideas from XML and the data format of electronic mail (RFC 2822).

SnakeYAML is a YAML parser and emitter for the Java programming language, and will be used to implement our message converter.

DESIGN

Let's start with a UML class diagram of HttpMessageConverter that are going to be implemented.

HttpMessageConverter is a base interface that must be implemented. It is a strategy interface that specifies methods to convert objects from and to HTTP requests and responses. AbstractHttpMessageConverter is the abstract base class for most HttpMessageConverter implementation (both provided by springframework), and is our base class.

First developed class is an abstract class called AbstractYamlHttpMessageConverter. This class is responsible of generic operations that "should" be required by all Yaml parsers/emitters. In my case it deals with charset options, and transforms HttpInputMessage and HttpOutputMessage to java.io.InputStreamWriter and java.io.OutputStreamWriter. In fact it acts as a Template Pattern to read and write operations (readInternal and writeInternal methods).

Next abstract class is AbstractSnakeYamlHttpMessageConverter. This class is a base class for HttpMessageConverters that use SnakeYaml as Yaml binder. This class gets an instance of Yaml class (central class of SnakeYaml project).

And finally JavaBeanSnakeYamlHttpMessageConverter. This class uses SnakeYaml JavaBeans features for converting from object to Yaml and viceversa. SnakeYaml does not support annotations like Jackson (JSON) or Jaxb (XML), but if some day this feature is implemented, we should create a new class extending from AbstractSnakeYamlHttpMessageConverter with required change.

CODE

First of all is adding a new dependency to pom. In this case SnakeYaml.

Then three classes previously exposed should be developed.

First class is a generic Yaml converter where we are setting accepted media type, in this case application/yaml, and creating a Reader and Writer with required Charset. We are leaving to children classes the responsibility of implementing read and write code.

Next class is specific of API that will be used to bind classes to messages, in this case SnakeYaml. This class will be responsible of creating an instance of Yaml class (from SnakeYaml). As is warned in http://snakeyamlrepo.appspot.com/releases/1.9/site/apidocs/index.html each thread must have its own instance; for this reason a ThreadLocal is used to carry out this restriction.

Final class is an implementation of read/write methods using SnakeYaml. As I have explained previously this class has a meaning because allows us changing SnakeYaml binding strategy (for example to annotation approach) and only worries to rewrite read/write operations.

Now it is time to register created message converter to AnnotationMethodHandlerAdapter. First thing you should do is not to use <mvc:annotation-driven>. This annotation registers default message converters and you are not able to modify them. So first step is comment or remove annotation-driven. Next step is declare DefaultAnnotationHandlerMapping bean and AnnotationMethodHandlerAdapter which registers http message converters. In our case only Yaml http message converter is added.

RUNNING

And now you can try application. Deploy it on a server, and using for example Rest Client, try http://localhost:8080/RestServer/characters/1 and you will receive a response like:

If you want you can use POST instead of GET to insert a new Character to our Map.

As you can see developing a Spring MVC HTTP Message Converter is so easy, in fact you must implement two basic operations, when a resource can be read or written and resource conversion.

Hope you found this post useful.

Download code

Music: http://www.youtube.com/watch?v=J8cr_CpuFO0

Can't you see, It all makes perfect sense, Express in dollars and cents, Pounds shillings and pents, Can't you see, It all makes perfect sense (Perfect Sense Part II - Roger Waters)

2011-10-04T09:09:00.000+02:00

REST INTRODUCTION

From Wikipedia: REST-style architectures consist of clients and servers. Clients initiate requests to servers; servers process requests and return appropriate responses. Requests and responses are built around the transfer of representations of resources. A resource can be essentially any coherent and meaningful concept that may be addressed.

As you have read the most important thing in Rest architecture is the existance of a resource. This resource can be anything (typically required information requested by client) that can be identified with a global identifier (URI in case of HTTP). In order to manipulate these resources, client communicates using standard interfaces (like HTTP) and exchange representations of these resources (using HTML, XML, ...).

Note that Rest does not force you to use any specific network protocol nor how resources are identified.

For those who have never read about Rest this description of Rest architecture could seem something strange and bit complicated.

A RESTful web service is a simple web service implemented using HTTP and the principles of REST. URI is defined as global identified, communication interface is HTTP and resource representation can be any valid Internet media type like JSON, XML or YAML. The set of operations that can be executed to resources depend on HTTP Methods and are (GET - retrieving/listing, PUT - replacing/updating, POST - creating and DELETE - deleting).

HANDS ON WORK

Let's create our first Rest application with help of Spring MVC. Imagine an application that has a database of manga characters, and you want to provide a Rest interface so clients can retrieve characters following a RESTful strategy.

First thing to do is identify the resource. In this case it is easy, "a character". Next step is finding a URI that determines unequivocally a character. Easy too de facto rule can be applied here. This rule suggests that a unique URI can be <host>/<applicationname>/<resourceName>s/<id> in our case to return (GET) character with id 1 the URI would be "http://localhost:8080/RestServer/characters/1". If no identifier is present all characters should be retrieved. If instead of GET, POST is used, a character with id "1" would be inserted. And finally decide which Internet media type is required, in this case doesn't matter because we are implementing both client and server so initially XML will be used.

CODING

Let's start with a simple Spring MVC application created with Spring MVC template. Not much secret here, you will have a servlet-context.xml where component-scan, annotation-driven and InternalResourceViewResolver are registered.

Next step is defining Character class. A simple POJO with four attributes. Class is converted to its XML representation using Jaxb annotation. Jaxb allows developers to map Java classes to XML representations and viceversa.

And finally the most important class in Spring MVC, "The Controller". Controller will be the responsible of implementing required operations of Character resource. In current case only GET is implemented, the other operations would be similar. Let's see the code:

First part is a map where all characters are stored. I have used this approach to not focus in data access. Then findCharacter method that is called when URI is /characters/{characterId}. This is a URI template and is a URI-like string, containing one or more variable names, which can be accessed using @PathVariable annotation. So when you are accessing to /characters/1 parameter characterId is bound to 1.

Last important part is @ResponseBody annotation. This annotation can be put on a method and indicates that the return type should be written straight to the HTTP response body, and not placed in a Model, or interpreted as a view name as standard behaviour of Spring MVC. So findCharacter method returns a Character object.

And that's all if you execute this code, and for example you enter URI http://localhost:8080/RestServer/characters/1 the output (using RestClient UI) will be:

And now is when you are wondering, ¿If I am returning a Character object and output is a XML, where is conversion between object and XML? So easy, let me introduce a new concept: HttpMessageConverters. HttpMessageConverter is responsible for converting from HTTP request message to an object and converting from an object to HTTP response body. Next HttpMessageConverters are registered by default:

- ByteArrayHttpMessageConverter

- StringHttpMessageConverter

- ResourceHttpMessageConverter

- SourceHttpMessageConverter

- XmlAwareHttpMessageConverter

- Jaxb2RootElementHttpMessageConverter

- MappingJacksonHttpMessageConverter

So now you understand why works perfectly. When you are returning Character instance, Jaxb2RootElementHttpMessageConverter using canWrite method checks if class contains XmlRootElement annotation. If class is annotated, write method is called. In this case Jaxb marshaller is called, and XML is returned. Same from XML to object but using Jaxb unmarshaller class.

So easy, no complicated configurations, no complicated mappings, no unclear code, and you only need to worry about your model objects, not in conversion. But let me introduce one change. Now instead of returning XML we want to return JSON.

Change could not be easier, add Jackson library to pom.xml and change @XmlRootElement to @JsonAutoDetect. And now MappingJacksonHttpMessageConverter will handle this object and will transform Character instance to JSON protocol using Jackson library. Only changing one line of code!!!

And now output will be:

CONCLUSIONS

Of course this is a very simple application with only one operation, but it gives you an idea of how to develop Restful web services using Spring MVC. It is a matter of time of writing all your required operations using same approach that I have used with GET.

Arriving at this point I think that all of us have arrived to same conclusion. Annotations are really really powerful, and Spring MVC fits perfectly for developing RESTful web services.

See you next time.

Music: http://www.youtube.com/watch?v=RiFC8nLfiUw

Download Code.

Ratti Ratti Sachi Maine Jaan Gavayi Hai, Nach Nach Koylo Pe Raat Bitayi Hai, Akhiyon Ki Neend Maine Phoonko Se Uda Di (Jai Ho - A.R. Rahman)

2011-09-28T08:32:00.002+02:00

Last week Spring Integration 2.1 M1 was released. One of new features is an implementation of MessageStorage interface that relies upon MongoDB for persistence.

In current post I will show you an example of Spring Integration using Claim Check pattern and MongoDB as storage system.

First of all a small introduction of each component we will use.

Spring Integration provides an extension of the Spring programming model to support the well-known Enterprise Integration Patterns. It enables lightweight messaging within Spring-based applications and supports integration with external systems via declarative adapters.

MongoDB is a high-performance, schema-free, document-oriented database, which stores JSON-like documents.

Claim Check pattern is an EIP pattern which allows you to replace message content with a claim check (a unique key), which can be used to retrieve the message content at later time. This pattern can be used when message content is very large and should be sent by request or when you cannot trust the information with an outside party and you use a claim check to talk with it.

As an example I have used a simplified version of Cafe Sample Application that are shipped with Spring Integration bundle, but adding MongoDB MessageStore.

In this diagram you can see a schema of sample application. First of all cafe component is the gateway, the point of entree to the system, and is connected to orders channel. Orders are sent to splitter, and each order is sent through pack channel. Last step is check-in component. This component is responsible to store order into MongoDB and generate an UUID. Finally UUID is sent to output (in this case console output).

Now I will show you the code of first part of application. I have assumed that you have already installed MongoDB on your system and is running.

Application context file contains Spring Integration beans that define structure defined above. See that the most important part is the definition of MongoDbFactory at line 18, and line 22 where we are defining database name (test database is created by MongoDB by default). The other part of file is self-explained. See that in line 37, claim check is defined and MongoDB message storage is referenced.

Next important piece of code is Cafe interface. This class acts as a facade for placing orders and not explained yet, for retrieving orders. Let's see this class:

Typical Spring Integration gateway class, where entering points are defined. For now line 7 is the most important because this method will be called for placing orders into orders channel.
And now you are ready to send orders using Cafe interface and receiving at console output not the order but an UUID.

This is a simple snippet that can be executed as unit test (in fact this is not a unit test I know, but for teaching purpose is enough). And if you execute it you will see two long numbers in console, something like:

Remember that number because is required in next step. Meanwhile orders are stored into database. If mongo console is opened, we can query test database and all orders stored will be returned.

Now that check-in has been implemented and tested, it is time to implement check-out method. In this example user (you) will enter UUID using console. Entered reference will be sent to input channel, order object with entered code will be retrieved from database, and sent it to stdout channel. Let's see the code:

Not much difference but instead of using claim-check-in we are using claim-check-out. In line 37 we are defining a gateway to enter UUID (recoverOrderAndSent method of Cafe interface). Introduced identification is sent to input channel and check-out is executed, consequently order with that identifier is sent to output channel (console output).

And our "test" now looks like:

Take a look, first of all two orders are sent to check-in component. Orders are saved to MongoDB and returned UUID are printed to console. Next step in that method is asking user to introduce one of previous UUID and order is checked-out.

And the output:

Note how simply is to configure your application to use claim-check pattern with Spring Integration, only configuring XMLs, without writing one line of code.. This is a simple example, of course you can use all the power of Spring Integration (aggregators, splitters, adapters, ...) with claim-check.

I wish you have found that post useful.

Download code.

Music: http://www.youtube.com/watch?v=NtDzUwVWQL0

Luna quieres ser madre Y no encuentras querer Que te haga mujer Dime luna de plata (Hijo de la Luna - Mecano)

2011-09-22T08:52:00.000+02:00

In previous post link I talked about aspects, concretely ITD, and how can be used to design your classes with its own responsibilities while maintaining source code clear and concise. In that post I used aspectj and spring-aspects as aspect-oriented implementations. An important concept of aspect programming is the process of weaven. An aspect weaver takes information from raw classes and aspects and creates new classes with the aspect code appropriately weaved into the classes.

If you are using Eclipse with AJDT plugin, weaver is executed automatically, but if you are using any build tool like Maven, you should take care of configuring correctly so generated classes contains aspect code too.

In this post I will explain how I have modified a pom file so compilation process also weaves aspect code into classes.

First thing I always do when I generate a pom file is adding component version in properties section. In this case spring and aspectj:

Next step is adding dependencies. To work with aspectj and spring-aspects four dependencies must be added.

But one more important dependency is required, and let me surprise you:

You can think I am joking, but not, JPA API is required. Here you can read why: https://jira.springsource.org/browse/SPR-6819. AnnotationDrivenStaticEntityMockingControl class requires javax.persistence.Entity to be in classpath. Hopefully nowadays most projects use JPA, so this dependency may already be required by your code, if not, then you should append it as dependency.

And finally aspectj-maven-plugin is registered:

This plugin requires that you define which dependencies will be used using <dependencies> tag. In order to apply already compiled aspects to your own sources you need to setup all JAR files you would like to weave in the plugin configuration using <aspectLibraries> section; in this case spring-aspects artifact is required so application can use capabilities that offer @Configurable annotation. Finally execution section should contain compile and test-compile goals so main and test classes can be woven.

Hope you find this post useful.

Alex.

Music: http://www.youtube.com/watch?v=HzeMbN90Pz8

The Bell That Rings Inside Your Mind, Is Challenging The Doors Of Time, It’s A Kind Of Magic (A Kind Of Magic - Queen)

2011-09-19T07:40:00.002+02:00

During class design we should take decisions about the assignment of responsibilities that will have every class. If we have chosen well, systems tend to be easier to understand, maintain and extend.

Almost all of our projects have a persistence layer, either relational database, document stores, or simply XML files. And typically you will use DAO pattern to implement abstract interface between your business objects and your data store.

In this post but I am going to explain another pattern that can be used instead of DAO pattern. Active record pattern is an architectural pattern that force you to implement CRUD operations on your model class, hence model class itself is responsible for saving, deleting, loading from database.

There are many strategies to follow to implement this pattern, but for me, the best one is using Aspect Oriented Programming, because we are still maintaining separation of concerns favoring isolated unit testing, and not breaking encapsulation.

Aspect-oriented programming entails breaking down program logic into distinct parts. These parts are known as crosscutting concerns because they "cut across" multiple abstractions in a program. Example of crosscutting concerns can be logging, transaction manager, error manager or splitting large datasets. For people that have worked with aspects not much secret here, to use them you simply create an aspect defining the advice and the pointcut, and your aspect is ready to be executed.

I guess most of us use aspects-oriented programming as I have described in previous paragraph, but will be fewer that uses ITD (Inter-type Declarations) feature.

Inter-type Declarations provide a way to express crosscutting concerns affecting the structure of modules enabling programmers to declare members of another class.

As we say in my country "bad said but well understood", ITD is a way to declare new components (attributes, methods, annotations) of a class from an aspect.

AspectJ is an aspect-oriented extension for Java. AspectJ supports ITD, and for this reason will be used in this post. Moreover I recommend you install AJDT plugin because it will help you develop aspects and having a quick overview of which Java classes are aspecterized.

If you have not understood what ITD is, don't worry, it is a typical example of concept that is best understood with an example.

Let's start with simple example:

Imagine having to model a car. You would have a car class, with some attributes, for this example three attributes (vin number, miles drived and model) is enough.

It is a POJO with three attributes and their getters and setters.

Now we want to add persistence layer, but in this case we are going to persist our POJOs in a XML file instead of a database. So Car objects should be transformed to XML stream. For this purpose JAXB annotations will be used. For those who don’t know, JAXB allows developers to map Java classes to XML representations and viceversa.

I am sure that first idea that comes to your brain is annotating Car class with @XmlRootElement (annotation to map root element in JAXB). Don’t do that, use aspects. Your first mission is trying to maintain Car file as simple as possible. To add an annotation using ITD, is as simple as:

With @type you are exposing which member is annotated. In this case only class. Other possibilities are @method, @constructor and @field. Then elements pattern that should be annotated, in this case Car class, but you could use any regular expressions like org.alexsotob..*. Finally the annotation.

Next step is using JAXB classes to marshalling/unmarshalling objects. In this example I am using spring-oxm package and briefly you will understand why. Spring-oxm is a part of spring-core that contains classes for dealing with O/X Mapping.

This spring module contains one class for each Xml binding supported. In our case Jaxb2Marshaller is used as marshaller and unmarshaller.

It is possible that you are thinking of creating a service class where you inject Jaxb2Marshaller instance. This service would include two methods (save and load) with Car class as argument or return value. Sorry but, doing this, you are implementing DAO pattern. Let's implement Active Record pattern approach. And as you may suppose, aspectj comes to rescue you to avoid mixing concepts in same source file.

Let's update previous aspect file so all required logic by JAXB will be in same file.

See that apart from annotating Car class we are creating two methods, and an annotated attribute. Attributes must follow same rule as methods, <class name> dot (.) and <attribute name>. Note that in this case attribute is transient because should not be bound in XML file.

Last step is configuring marshaller in spring context file.

Not much secret. Now let's code a unit test.

Run junit class and BOOM all red, with an amazing NullPointerException. Marshaller is created in Spring context, but not injected into Car class (Car is not managed by spring container, so is impossible to be injected). And now I suppose you are telling yourself: "I told you a service layer would be better, because it would be managed by Spring and autowired would work perfect.". But wait and see. How about using spring-aspects module? Spring Aspects contains an annotation-driven aspect (@Configurable) allowing dependency injection of any object, whatever is or not controlled by container. So let's apply last two changes and the application will run.

First of all is creating a new aspectj file to annotate Car class as Configurable.

And finally modify spring context file to allow @Configurable annotation.

Adding <context:spring-configured></context:spring-configured> namespace is enough. As a result, any time you instantiate an object (via the "new" keyword), Spring will attempt to perform dependency injection on that object.

Now run unit test again and green will invade your computer :D.

ITD is a really nice solution to design classes with its own responsibilities. It gives you the oportunity of writing maintainable and understandable code, without loosing encapsulation. Of course you should take care of not to have high coupling in aspected classes, and convert them in "God Classes".

Note that implementing same approach but using relational database, it is as simple as changing Jaxb2Marshaller to EntityManager.

I wish you have found this post useful.

Download Full code

Music: http://www.youtube.com/watch?v=KLFZzInXAWI

Questa di Marinella è la storia vera Che scivolò nel fiume a Primavera Ma il vento che la vide così bella Dal fiume la portò sopra una stella (Canzone Di Marinella - Mina)

2011-09-12T08:23:00.000+02:00

Most of us use Maven as a build automation tool. One of most important section are those related to dependencies. Typically projects have dependencies to external libraries like Spring, Hibernate, Slf4j, ... which are downloaded from External Maven Repository Servers like mvnrepository, ibiblio or from own Internal Maven Repository Server using JFrog or Nexus. This scenario but does not cover all possible cases.

It is uncommon that your project requires an external library that is not present in any repository, but can occurs, and in these cases are where you use company Internal Maven Repository to upload these artifacts. But this is not always possible, and typical example is when you are writing in a blog about a beta library and it is not present in any repository, and you want to add this library to pom file. Would be perfect if Maven could resolve these dependencies too without packaging them into project. So what can we do?

There are some alternatives:

- packaging .class files of external library into your project, so they are packaged as project files.

- asking library creators to upload Milestones to public repositories.

- create your own public Maven Repository.

- using GitHub?

Using GitHub, YES!!. You can configure your GitHub account as Maven Repository. In my case I always upload sample code to GitHub. Why not creating a GitHub project that acts as a Maven Repository and poms referencing to this repository?

Now I will summarize steps that shall be followed: (assuming that you have already created a project).

Create a GitHub repository.
Initialize local directory as Git repo.
Modify project pom so distribution management tag points to local repository.
Perform deploy goal so artifact is deployed to local repository.
Push changes to GitHub.
Nothing more. Now other project poms can use your repository.

Let's get down to work:

The first thing you should know is that the project I want to upload to Maven Repository is located at /media/share/workspace/github-test and project that will have a dependency will be located at /media/share/workspace/bar.

First step is creating a new GitHub repository. So login to your GitHub account and create a new repository. In my case I have named maven-repository.

Second step is initialize local directory as Git repository.

Third step is adding distributionManagement tag pointing to repository so when project is deployed, artifact is created to Git directory.

See that url tag is pointing to previously created Git directory (local disk).

Fourth Step is running mvn -DperformRelease=true clean deploy. Project is compiled, tested, and packaged. Now go to local repository and see what has appeared.

Fifth Step implies two operations, committing changes and pushing them to GitHub.

See that first command is adding root directory. Then all files are committed to local repository and pushed to GitHub repository.

Sixth Step if you want to call it step, is adding repository tag to project that requires published component. In our case bar project requires it.

This pom represents a project that wants to use github-test module. It is important to note that repository url is special (not showed when you explore GitHub projects with navigator), and is https://github.com/maggandalf/maven-repository/raw/master. After repository name (in this case maven-repository) you should concatenate /raw/master. raw because you want to access to files without any decoration (no HTML), and master because it is the branch name.

When bar project is being compiled, github-test artifact is downloaded.

I think it is a good approach when you need to upload a Maven artifact temporally, or simply because your project requires a milestone version of artifact that is not uploaded into any repository.

I hope you like this post, and ... MOVE TO GIT.

Music: http://www.youtube.com/watch?v=TL69oTe6HHY

Soy El Capitán De La Nave Tengo El Control, Llamando A La Tierra Esperando Contestación, Soy Un Cowboy Del Espacio Azul Eléctrico (Llamando A La Tierra - M.Clan)

2011-09-06T21:33:00.000+02:00

Groovy is an object-oriented programming language for the Java platform and can be used as a scripting language. Most of us but instead of using Groovy alone, we use Grails (web framework based on Groovy) for developing web applications.

But Groovy can be used standalone for developing your internal tools. Let me explain why Groovy scripts have simplified our development of tools for generating data for integration tests.

In my company we create clinical instruments. These instruments are so expensive, and big enough to say that they are not portable. For these reasons each instrument has an emulator, so integration tests are run without having physically any instrument.

Our emulator has an XML file where all required resources for running tests are configured. In summary each file contains a list of blood barcodes, and reagent barcodes. In our case barcodes have a meaning (kind of resource, expiry date, checksum, ...).

So one can think about creating a standard configuration file that is used in integration tests. It is a good idea if you don't know that expiry date is expressed in months. So one day without knowing exactly why your tests begin to fail. The answer is obvious, resources have become expired. We need a (script ?) that updates this XML file so when a resource is becoming expired, its month field is changed.

Moreover not all resources should be updated. Some tests imply working with expired resources. For this reason some barcodes have special format that suggests that update should not be applied.

Because project is developed in Java, one can think about creating a small Java class that do all these work. But wait and think if this class would be small or not, we need a parser (DocumentBuilder), a method that walks all nodes and see if resource is expired or not (NodeList, Element.getAttribute(), ...), and finally writing modifications to file. Furthermore, some barcodes contains special charachtrs that should be detected using a regular expression (Pattern, Matcher) for avoiding its update. Although this class is not difficult, it is far away from a small class with few lines.

But how about polyglot programming? Groovy can be a choice. Let's see how Groovy deals with XML and Regular Expressions.

Imagine next XML file:

Groovy and XML

Meanwhile in Java you create a DocumentBuilderFactory that returns a DocumentBuilder, and then call parse method, in Groovy is as simple as:

and root variable points to root element of XML file.

And now imagine that you want to update all blood barcodes of given holder. With Java you will use an iterator over NodeList or using an XPath expression. See the simplicity with Groovy.

See that with Groovy, nodes are explored as object attributes, and finally we call findAll() method that returns a list of sample nodes belonging to SampleHolder11 tag. For returning an attribute value is as easy as adding @ character before attribute name, in our case barcode.

And for writing an XML is as easy as:

In previous example, output is written to console.

Groovy and Regular Expressions

Remember that some barcodes have special format. In our case if any barcode starts with A, B, C or D, should not be modified. A clean, reusable and maintainable solution is using regular expressions to check if one barcode matches or not special format. In Java the process is not banal, you have to create a Pattern object with a regular expression, a Matcher and use find() method to see if pattern is found on entry or not.

But how we can determine if one string matches a regular expression in Groovy ? ==~ operator does the work for us. Tell me what you think about this expression:

Elementary. You will agree with me that Groovy approach is simpler than Java one. For specifying a pattern you only have to use ~ character plus a slash (/) then a regular expression and finally a slash to delimit. But Groovy also supports =~ (create a Matcher) and ==~ (return boolean, whether String matches the pattern).

I think that creating a script that reads/parses/writes XML file is so fast and easy, not much classes are involved compared to Java. And not worth making the comparison with regular expression approach, in Groovy is the simplest way one may think.

After the success of previous Groovy script, we decided to create another tool (Groovy script) for manipulating database.

System registers into database every incidence that has occurred to an execution. Some incidences are easy to reproduce with emulator, but others not. In integration tests there is no problem, because a defined-filled database is used, but acceptance tests contains no data and is generated with the execution of tests. But because there are some incidences that are hard to reproduce in emulator, a Groovy script to insert incidences are created.

Groovy and SQL

As Java, Groovy can also access to databases and as you can suppose in a simple way. No Connection object, no PreparedStatement, no ResultSet, ....

Let's see an example of searching data and using them for creating a new registry. Imagine that we have a table called Execution and another one called Incidence, and one-to-many relationship.

Simple, yes? With one line a connection to database is established.

Executing SELECT query and iterate over results are also easy. Using eachRow method, all results are iterated. No ResultSet object is required anymore. Parameters values are passed between brackets ([]), and as XML each row is accessed using Closure. In previous example each row is mapped to execution variable. Moreover see how easy is read a value of each tuple. As in XML you access the value as a class attribute, no more getters of ResultSet methods, in example execution.dboid is used to refer to dboid field.

Finally execute method is used to update database.

Now that I have shown you some of nice features that Groovy offers us, I will explain you how we execute these tools.

GMaven

We use Jenkins with Maven as Continuos Integration System. Before Jenkins starts to execute Integration Tests, Groovy scripts are executed so emulator is configured propertly. The iteresting part of this step is how pom is configured for executing Groovy scripts.

Exists a plugin called gmaven-plugin. This plugin runs Groovy scripts depending on phase and goal.

No problem configuring gmaven plugin, the most important part is where you specify which script should be executed.

As final notes I want to say that I am a huge fan of Java and my intention is not criticize it, but I think that there are some problems that are best suited using other languages rather than Java. My advice is learning as many kind of languages as you can (Scala, Groovy, ...) so as programmer you can choose the best solution to a given problem.

I wish you find this post useful.

Music: http://www.youtube.com/watch?v=9u54Xs22_SI

Tu I Jo Asseguts A La Barra D’un Bar, Sona Bona Música I Som Davant Del Mar (Al Mar - Manel)

2011-07-22T09:20:00.001+02:00

In current post I am going to talk about differences between Hamcrest and Fest Fluent Assertions. The reason of this post is not to tell you if you should use one or the other. I only want to show you how both implementations resolve the problem of writing readable assertions.

To compare both APIs I have created two JUnits, one using Hamcrest assertions and one where Fest assertions are used.

The comparision is done using only common operations (Logical, Object, Collections, Number, Text) and creation of new matchers. I am not going to compare which ones have implemented more matchers or kinds of matchers, because I think this is not a parameter to use for choosing what library fits better to your project. Moreover in both APIs you can extend them for creating your own matchers.

Let's start showing model representing a simple modelling of Studio Ghibli http://en.wikipedia.org/wiki/Studio_Ghibli movies information.

Imports:

Hamcrest requires 11 imports:

while Fest requires 2 imports:

in fact this is not a good or bad thing how many imports are required, but it is always a headache remember where a required assertion is packaged. Because Fest uses Fluent Interfaces approach with two imports all operations are available with IDE's "auto-completation" feature.

Simple asserts:

Not much difference between Hamcrest and Fest, in case of Fest verb is also added in method name creating a much readable assert.

Hamcrest

Fest

Logical asserts:

In this case we find a big difference. Hamcrest supports logical operations and can be used independently, meanwhile logical operations in Fest are a part of the method:

Hamcrest

Fest

Object asserts:

Same object operations are provided in both APIs. There is only one difference, in Fest you can chain callings of methods, so number of asserts compared to Hamcrest are fewer.

Hamcrest

Fest

Collection asserts:

In case of Collections is where they differ more from each other. Hamcrest deals with Collections and Maps with methods like hasKey, hasValue, hasItem. Fest uses a more generic calling like includes, excludes, entry; I have not found any way for asserting key instead of key-value in Fest.
Moreover in this example I also compare how to access a bean property in each elements of collection. From my point of view I think that Fest has a better approach resolving this case.

Hamcrest

Fest

Number asserts:

As in simple asserts, there is no much difference between them.

Hamcrest

Fest

String asserts:

Hamcrest

Fest

As you have noted Hamcrest and Fest are very similar, but I think that Fest solves the same problem but in much cleaner way.

Although both solutions offer very similar matchers, each implementation is so different, so creation of a custom matcher is different too. In Hamcrest you should create a class that extends from TypeSafeMatcher. In Fest there are two possibilities, first one is extending Fest-assertions with custom condition (using already Fest structure and defined types), and the second one is extending with custom assertion (creating a new assertThat implementation for required type).

Hamcrest extension for asserting that a character is a human:

In case of Fest there are two approaches, the first one, that requires that our class extends from Condition. As I told previously, extending Condition implies using the same kind of types supported by org.fest.assertions.Assertions.assertThat method (object, int, short, list, array, ...). In previous case our type is Character, and of course does not exist an overload of Assertions.assertThat method with Character, but java.lang.Object. So our class should be:

As you probably noted, you need to cast character variable to Character, neither a clean solution nor optimal. But of course you can use second method, extending from GenericAssert. This class (a Fluent class) will be the responsible of implementing an assertThat that accepts Character objects, and moreover will implement matcher methods. And I say methods because unlike Hamcrest, Fest can contain more than one matcher in each class. For example if there are some tests that we are asserting if character is human, and in another ones asserting if is human and if has a name, in Hamcrest we should create two classes. In Fest you don't have this restriction.

As it is told in Fest site "Which one to use? Hamcrest or FEST-Assert? It is up to you...it depends on the needs of your project and your coding style!"

Download code.

Music: http://www.youtube.com/watch?v=GjWLXZ4WdQU

Umetxoak Ikusirik Lorea Ezin Bizirik Arantzak Kendu Nahi Dizkio Bizi Berri Bat Eman (Loretxoa - Benito Lertxundi)

2011-07-04T08:44:00.000+02:00

EJP (or Easy Java Persistence) is a powerful and easy to use relational database persistence API for Java. It has no need for mapping Annotations or XML configuration, and there is no need to extend any classes or implement any interfaces. In it is site we can find the following statement: "EJP is, by far, the easiest persistence API available for Java."

From my point of view EJP is a mixture of some features between myBatis and Spring Jdbc Template Row Mapper.

An example of EJP from its website:

and Customer and Support classes are simple POJOs without annotations or any special tag, and no configuration file.

What I am going to explain in this post is how integrate EJP with Spring.

First of all, we are going to create an interface which defines all permitted operations:

This is an example of common operations provided by EJP. Methods that should be clarified are:

newDatabase method is used for returning a Database object. This object is a facade that implements all operations supported by EJP. It is the main class of EJP project with permission of DatabaseManager class.
loadAssociations are responsible (as its name suggests) to load an object associations.
queryForObject methods execute a "query by example" queries.
queryForInt is a method used for queries that return numerical results like count(*), avg(...), ...

EjpJdbcTemplate is the implementation of previous interface, and makes use of JdbcTemplate class as core.

Getting a new Database:

Remember that Database object is the core of EJP, and is required to execute all EJP operations. This method creates one Database with given Connection. databaseName is not mandatory, but for no reason is a constructor attribute. A null can be passed without any problem. In this implementation database name is a class attribute.

Deleting:

No secret in deleting an object. Using ConnectionCallback, connection is provided, and Database object is created.

Loading Associations:

If you want to load explicitly all associations of an object, load associations method must be called. The only integration difficult is that database.loadAssociations returns void, and ConnectionCallback should always return a result. In this case void.TYPE is used.

Executing Queries:

In this case most important line is where Database executeQuery method is called. This method returns a class of type Result. This class is a wrapper of ResultSet class but also can deal directly with beans (implicit wrapping), instead of getting one-by-one each parameter. But for following JdbcTemplate strategy and use a row mapper, ResultSet is used for mapping results.

Querying for Int:

See that follows the same schema as executeQuery, but instead of using RowMapperResultSetExtractor, a SingleColumnRowMapper is used. This mapper is used when the query result returns a single result.

Now I am going to show how to use this template into a DAO implementation.

Not much secret in this DAO. Only two methods requires special review findAllCustomersOrderedByName() and findCustomerByExample()

The first one:

this.template.queryForObject(Customer.class, "ORDER BY first_name",BeanPropertyRowMapper.newInstance(Customer.class))

is converted by EJP to SELECT * FROM Customer ORDER BY first_name.

The second one:

this.template.queryForObject(customer, BeanPropertyRowMapper.newInstance(Customer.class))

instead of receiving a Class it receives an instance itself to execute the query. In case that first name field was set to alex, the equivalent SQL query would be SELECT * FROM Customer WHERE first_name='alex'

Now I have explained a strategy to integrate EJP with Spring. Because I have followed same structure as Spring-Data Jdbc-Extension project, rather than create a "HelloWorld" project, I decided to fork Spring-Data project into my Github account, and uploaded the code as a new extension for the project. Moreover a Jira issued has been created with id DATAJDBC-11. If you want to watch full code and unit tests go to git@github.com:maggandalf/spring-data-jdbc-ext.git and review spring-data-jdbc-ext/spring-data-jdbc-core/src/main/java/org/springframework/data/jdbc/ejp directory.

I wish you have found this post useful.

Music: http://www.youtube.com/watch?v=PlEknDUSRc0&feature=fvwrel

Tonari No To To Ro Totoro To To Ro Totoro, Kodomo No Toki Ni Dake Anata Ni Otozureru, Fushigina Deai (Tonari No Totoro - Ghibli Songs)

2011-06-20T08:50:00.005+02:00

Spring Framework 3.1 M2 has been released past week. This new release is the last milestone, and next versions will be tagged as RC.

This new version completes the work started in M1, and adds some new functionalities.

To summarize them we can name:

Configuring Spring Web MVC application without web.xml (post).
Cache abstraction has been revised.
A new "packagesToScan" feature for JPA.
REST support refinements with respect to URI templates.
And many more refinements.

In current post I will talk about Java-based container configuration approach to setting up a Spring Web MVC application.

As a reference application we are going to migrate Spring MVC Template Project to 100% Java-based container configuration.

If you are using STS, you can create a new Spring project from Spring Template Project wizard:

One of these templates is for creating a Spring Web MVC application. In my STS version, this template creates a XML-based container configuration project.

As you have already noted, important elements of this project are:

HomeController that redirects to home.jsp page.
web.xml file where Spring DispatcherServlet (loading servlet-context.xml) and ContextLoaderListener (loading root-context.xml) are specified.
root-context.xml defining shared resources visible to all other web components.
servlet-context.xml defining servlet's request-processing infrastructure, and importing controllers.xml configuration file.
controllers.xml as its name suggests configures controllers.

What we are going to create is a revision of Spring MVC Template Project that instead of setting up project using XMLs, is configured using Java classes. The new directory structure is:

If you look carefully, under src/main/webapp directory, there are no XML Spring configuration files. And no web.xml, but I will talk about that later. For now imagine that under WEB-INF there is a web.xml file.

See that structure is very similar to previous one, but spring directory is removed and config package is created. Moreover XML files have been converted to standard classes.

Again ignore strange WebAppInitializer class that has appeared. Let's see applied changes:

root-context.xml has its equivalent with mytld.mycompany.myapp.config.RootContextConfig.

Most important thing in previous class is @Configuration annotation. This annotation indicates that the class can be used by the Spring IoC container as a source of bean definitions.

Class that replaces servlet-context.xml file is:

I am going to show you servlet-context.xml content so you can ensure that XML and Class contain the same parameters.

Apart from @Configuration annotation, this class is annotated with @EnableWebMvc, which enables @Controller programming model, and @Import for importing other bean definitions, like servlet-context.xml imports controllers.xml. This class extends from WebMvcConfigurerAdapter because some extra configuration is required. WebMvcConfigurerAdapter defines options for customizing or adding to the default Spring MVC configuration. In summary it provides customizing parameters as mvc namespace does. In our case, as servlet-context does, we define static resources path to /resources/, so we only override configureResourceHandling method. If for example we would like to register interceptors, configureInteceptors method should be overridden. And finally @Bean is used for creating the view resolver bean. @Bean methods define instantiation, configuration, and initialization logic for objects to be managed by the Spring IoC container.

Next class is called ControllerConfig and is the responsible of registering controllers. In this case @Bean approach is used because component-scan is not supported directly. Anyway you can use scan method of AnnotationConfigApplicationContext for same purpose but in this case first choice has been chosen.

And finally web.xml must be changed for loading Java-based configuration instead of XML-based ones. In this case contextClass parameter of DispatcherServlet and ContextLoader listener must be changed to AnnotationConfigWebApplicationContext so Spring IoC Container can load beans from configuration classes, and contextConfigLocation must be pointing to configuration classes, and not XML files.

And I suppose you are wondering why in previous directory structure cannot be seen web.xml but WebAppInitializer class. This is explained in my post, and is another new feature of Spring 3.1 M2, that you can configure a Spring Web MVC application with no web.xml.

So if you want a 100% Java-based configuration, simply removes web.xml file and creates the WebAppInitializer class, which looks like:

As you can see, same elements of web.xml are present but they are configured in a programmatic way.

Hope you find the post useful, of course you can create hybrid applications, mixing elements configured in XML way and other ones configured in Java classes.

Two Spring Template Projects are provided, one configuring Spring MVC application in a Java-based fashion and web.xml, and another one 100% Java-based configured.

Spring Template Project with web.xml
Spring Template Project no web.xml

Music: http://www.youtube.com/watch?v=KzLDdof7U8M&feature=related

It's Strange But It's True, I Can't Get Over The Way You Love Me Like You Do, But I Have To Be Sure, When I Walk Out That Door (I Want To Break Free - Queen)

2011-06-15T08:34:00.000+02:00

Spring Framework 3.1 M2 has been released past week. This new release is the last milestone, and next versions will be tagged as RC.

This new version completes the work started in M1, and adds new functionalities.

To summarize them we can name:

Java-based application configuration approach has changed from the @Feature approach in M1 to @Enable* annotations (I will talk about this in next post).
Cache abstraction has been revised.
A new "packagesToScan" feature for JPA.
REST support refinements with respect to URI templates.
Many more refinements.

In current post I will talk about one new feature that will allow us to configure Spring Web MVC application without web.xml.

With Servlet 3.0 specification, web.xml is not required anymore, you can configure your servlets using @WebServlet annotation. Prior to Spring 3.1, DispatcherServlet should be declared and configured in web.xml, so although our application was deployed using Servlet 3.0 specification, web.xml was "a must". With Spring 3.1, things are different. You can use WebApplicationInitializer approach for bootstrapping a Spring web application without web.xml.

First of all let’s take a look at traditional way (using web.xml).

No problem here, if you have developed applications using Spring MVC this file will sound you familiar.

But now let’s use WebApplicationInitializer approach.

Spring 3.1 comes with WebApplicationInitializer interface, that must be implemented in Servlet 3.0 environments in order to configure the ServletContext programmatically - as opposed to (or in conjunction with) the traditional web.xml-based approach.

What we need is a class (can be created in any package, next I will explain why!!!) that will implement WebApplicationInitializer. Our equivalent class to previous web.xml is:

See that same information is required, but is provided programmatically instead of using web.xml. Spring application context must be created by you setting config file/s location, DispatcherServlet is still valid and must be registered too using addServlet method, and of course context-param can be added using setInitParameter method. And only creating this class that implements WebApplicationInitializer, you can remove your web.xml from your application.

Look ma' no web.xml and Spring Web application is still working. And now let me explain why if our class is not configured anywhere and moreover is created in any place (inside classpath), is instantiated and its onStartup method called? Servlet 3.0 ServletContainerInitializer is designed to support code-based configuration of the servlet container at startup phase. Spring people have created SpringServletContainerInitializer class that implements ServletContainerInitializer, and this class will be loaded and instantiated and onStartup method invoked by any Servlet 3.0-compliant container during container startup. This occurs through the JAR Services API ServiceLoader.load(Class) method detecting the spring-web module's META-INF/services/javax.servlet.ServletContainerInitializer service provider configuration file.

Hope you like this new feature.

Note: Servlet 3.0 container is required (for example Tomcat 7), and versions of Tomcat <=7.0.14, root mapping ("/") cannot be used.

Download Code.

Music: http://www.youtube.com/watch?v=Odk3W3qLByI

Y Hay Un Decano También, Y Un Abogado También, Y Un Policía Rodeado De Ladrones (La Taberna del Buda - Café Quijano)

2011-06-14T07:49:00.000+02:00

Due to the advent of mobile internet, a variety of devices have connection to the world (mobiles, pads, GPS, netbooks, ...), and these devices could not be as powerful as desktops/notebooks. For this reason, keeping web pages as lightweight as possible is a must. Improving the engineering design of a page or a web application usually is the biggest savings and that should always be a primary strategy. With the right design, some other strategies can be followed. One of these is code minification.

Now-days, jQuery are becoming so popular in client-side of web development. jQuery is a cross-browser Javascript library designed to simplify the client-side scripting of HTML. jQuery itself is composed by "one" file. Thanks of that boom, Javascript is becoming more important when a web interface is developed.

Have you ever opened jQuery Javascript file? Let me tell you what you will see. Nothing human readable, all code occupied only one long line, and variables and methods name are as short as possible:

See this example:

Of course, there is no developer in the world (or at least I wish), that could write this code. So where this code comes from? It is so easy, it comes from a Javascript minifier tool.

The goal of Javascript and CSS minification is always to preserve the operational qualities of the code while reducing its overall byte footprint

There are a lot of tools designed for minifying Javascript files. One of these are YUI Compressor from Yahoo. From its site:

“The YUI Compressor is Javascript/CSS minifier designed to be 100% safe and yield a higher compression ratio than most other tools. Tests on the YUI Library have shown savings of over 20% compared to JSMin (becoming 10% after HTTP compression).”

Because the growth of popularity of jQuery, and HTML 5/CSS3, client-side coding is playing an increasingly important role in web development, and one of these consequences is that in client-side you could need to develop some custom Javascript files, apart from using already developed Javascript libraries like jQuery. And then the question is, if jQuery minify their files, why I cannot do the same with my Javascript/CSS files? And the answer is: “Yes you are right”, and also I say: “We will automatize this process into Maven, so your web project will be packaged with minified scripts”.

Let’s start with a very simple “Hello World” script file:

If you execute manually YUI Compressor as standalone application (java -jar yuicompressor-x.y.z.jar), script is minified to:

output: myscript.js (115b) -> myscript.js (54b)[46%]

Now our script is 46% smaller than the first one, of course the price we are paying is that we are loosing readability, but in production environment makes no sense.

Next step is configuring your pom.xml (Maven) so when application is packaged, all packaged Javascript files are minified. For this porpoise yuicompressor-maven-plugin (http://alchim.sourceforge.net/yuicompressor-maven-plugin/) plugin comes to rescue you.

No secret here, plugin is executed in generate-sources phase, and is configured with no suffix option because I want that “compressed” file has the same name as original one, and also I don’t want any line break in minified file.

And finally the last trick, maven-war-plugin configuration should be changed for avoiding it replaces minified files for original ones.

In this case scripts are in src/main/webapp/script so excluded sources are script/*.js. yuicompression plugin will copy minified files into target directory that will be used by war plugin for building war file. For this reason we should avoid that war plugin also copies the original file to target directory, replacing the good ones (compressed) for the bad ones (uncompressed).

If you read my previous post, where I talked about decreasing download time of Javascript/CSS files(using aggregation) and also I explained why not to use an automatic approach in development time but in running time, I suppose you are wondering why I am explaining in this post minification using Maven? Well let me explain, YUI Compression should be used in conjunction with aggregation files. YUICompressionplugin supports aggregation too, so if you are developing a public API it is a good approach using YUICompression (using Minifing and aggregation) with Maven. But if you are developing a website, the best approach is applying optimizations at runtime using Jawr API as I explained in my previous post. But next question is how to use Jawr (by default it uses JSMin) with YUIcompression? The response is easiest one anyone could think, Jawr also supports YUI. Only one line should be added, open jawr.properties and copy next line:

jawr.js.bundle.factory.bundlepostprocessors=YUI

Now Jawr will minify aggregated file using YUI Compression instead of JSMin.

Hope you find post useful.

Music: http://www.youtube.com/watch?v=K_mJ1NgqiSk

I Hitched A Ride With Chris McCandless, I Stepped In The Wild With Chris McCandless, And I Felt Alive With Chris McCandless. I Was Wide Awake In The Dream. (The Ballad of Chris McCandless - Ellis Paul)

2011-06-06T08:01:00.001+02:00

Now-days, jQuery are becoming so popular in client-side of web development. jQuery is a cross-browser JavaScript library designed to simplify the client-side scripting of HTML. jQuery itself is composed by "one" file called jquery-x.x.x.min.js. With only one Javascript there is no performance problem. But with jQuery has been appeared some "addons/plugins" that uses this library. An example could be jQueryUI http://jqueryui.com/ but more can be found at http://plugins.jquery.com/. Each of these addons contain their own Javascript file. For example jQueryUI contains apart from jQuery file, jquery-ui-x.x.x.custom.min.js and one CSS file, so in this case in a web page two Javascript and a CSS elements are defined. As more and more extensions are used, more Javascript files are required. And more scripts imply more connections to server, so for example if three Scripts and one CSS are defined, four connections from browser to server are required.

Because of these amounts of connections, downloading time is increased; content negotiation and the fact that normally there will be only two concurrent connections to the same host, produces an overhead that results in a long page loading time. For example, it is faster to serve a 8KB script file than eight of 1KB.

For speeding up your application, would be desirable that only one Javascript and one CSS were downloaded. Arrived at this point, one can think next approach; using a Maven plugin or any other automatic system, that opens all js files and concatenate all of them in a single file. This approach is valid, but has a major problem, any small change forces developer to re-run build script before changes can be tested. Also you are duplicating same information in two or more files, so you must take care assuring consistency between them.

The goal for Jawr is to provide a system to easily map resources to bundles using a simple descriptor, and a tag library to import these bundles to JSP pages.

In summary, using Jawr taglib you define a fictional Javascript file (for example widgets.js) in JSP; this file does not exist physically anywhere. Then in Jawr configuration file (jawr.properties), you map which Javascript files should be appended when client browser requests "unreal" Javascript file (widgets.js). So from developers' point of view you could have a hierarchy of several js files, while from client-side (browser), only one file is sent.

Using Jawr in only Servlet based web applications are easy. Jawr comes with a Servlet net.jawr.web.servlet.JawrServlet, where you define Jawr configuration file, and a workable mapping for js extensions. (http://jawr.java.net/docs/servlet.html).

But in case of Spring MVC web applications, things are bit complicated. Jawr provides a Spring controller, that acts the same manner as previous Servlet, but instead of using servlet-mapping tag you must create a SimpleUrlHandlerMapping.

In this post I will explain you how to create a Spring MVC jQuery web application integrated with Jawr. Let's start with a Spring MVC application that does not contain any references to Jawr.

JSP page contains definitions for all elements required by jQuery plus one custom script file (defining a() function).

and in servlet-context.xml static resources (Scripts and CSS) mapped correctly.

This web application contains four references to static resources, so load diagram looks like:

As you can see there is no file aggregation. With Jawr these four connections can be reduced to two, one for all Javascript files and another one for CSS.

Let's start mapping resources. This is specified in jawr.properties file that should be present in root classpath:

First line enables the ability to serve gzipped resources to browsers that support it. Next two lines are required for mapping script files. jawr.js.bundle.[bundleName].id is the property where you specify the name of fictional Javascript file. This name will be the one used in JSP. The other line jawr.js.bundle.[bundleName].mappings is where you indicate all Javascript files that should be appended when jawr.js.bundle.[bundleName].id file is requested by browser. In previous example when your JSP page is requesting /script/all.js resource, Jawr will join a.js, jquery-1.5.1.min.js and jquery-ui-1.8.13.custom.min.js and sent back the result to client-browser. Last lines are the same but for CSS files.

Next step is changing JSP, so instead of having one reference for each file, only contains one reference to jawr.js.bundle.all.id value.

Jawr provides a tag library used to generate tags that import bundles to clients and these tags are <jawr:script/> and <jawr:style/>.

Unlike Servlet approach, web.xml don't have to be modified, Jawr provides a Spring controller that must be configured as you would do in Servlet approach.

Next step is configuring Spring Controller. Jawr site provides documentation about how to configure a Spring MVC with Jawr. The example provided uses old-school fashion configuration controllers using SimpleUrlHandlerMapping. But because I always use annotated controllers and I don't want to have some controllers defined with annotations and other ones in UrlMapping, in this post Jawr Spring Controller has been extended for being used with annotations.

For implementing Jawr Spring Controller with annotations I have only created an aggregation between annotated controller and Jawr controller. So class looks:

and the same approach for CSS is used but changing RequestMapping to /**/*.css and Qualifier to jawrCSSController.

As you probably noticed, two Jawr controllers are used, one for Javascript and another for CSS. This is because Jawr requires that you specify if code to optimize is Script or StyleSheet. Spring configuration looks:

Finally <resources> tag from servlet-context.xml should be changed to:

<resources mapping="/css/images/**" location="/css/images/" />

because now only images are required to be served as static resources.

With previous changes applied, load diagram looks like:

See that only one connection for all Javascript files are performed. And also see how downloaded time has been improved from first version. Times showed here are not calculated in a scientific way, they are calculated from localhost, but if you compare previous diagram with this diagram, you can see an improvement.

You can also speed up even more your response time using a cache strategy, but this topic is out of scope of this document.

I wish you have found this post useful, and now before using jQuery scripts, prepare your environment with Jawr so your application can be loaded even faster.

I hope you find this post useful.

Download Code.

Music: http://www.youtube.com/watch?v=3tdQx4Y3I2c

If There's A God In The Sky Looking Down What Can He Think Of What We've Done To The World That He Created (Is This The World We Created - Queen)

2011-05-28T11:14:00.002+02:00

Hello, this week I have reached 25K visits. Not long ago, I wrote that I have reached 10K visits during Japan earthquake. Now thankful Japan nuclear crisis seems that has passed.

I would like to say thank you to all people that have read my blog, specially people from theserverside.com and springsource for publishing my posts on their site, and also people that have become followers of my blog.

For now that all, I wish I reach 100K as soon as possible, thank you very much all of you for your support.

Alex.
Music: http://www.youtube.com/watch?v=pUOrAengPH8

Mornië Utúlië, Believe And You Will Find Your Way (May It Be - Enya)

2011-05-27T18:57:00.000+02:00

A CAPTCHA is a program that can generate and grade tests that humans can pass but computer programs "cannot". One of strategies followed are showing an image to user with distorted text, and user should write text in input area. If showed text is the same as input by user, then we can "assure" that a human is on computer. A captcha example:

Captchas have several applications for practical security, for example:

Preventing Spam in comment fields.
Protecting from Massive User Registration.
Preventing Dictionary Attacks.
...

These distorted texts are acquired as follows:

Digitizing physical books/newspaper.
Pages are photographically scanned, and then transformed into text using "Optical Character Recognition" (OCR).
OCR is not perfect, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA.
Word that cannot be read correctly by OCR is given to a user with another word for which the answer is already known. Then is asked to read both words, if user solves the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct.

Now you know how captcha works, the problem is that if you want to use captchas in your website, you should implement yourself process described above, and of course this is not easy and tedious work is required digitalizing works. For this reason there are some "captcha providers" that have done this work for us. One of these providers is reCaptcha http://www.google.com/recaptcha. reCaptcha is a free captcha service that provides us these captchas ready to be used in our site. As developers we only have to embedded a piece of code in client side for showing captcha image and text area, and in server side, calling a function for resolving input data. reCaptcha provides plugins for dealing with lot of programming languages like Java, PHP, Perl, ...

This post will guide you on how to use reCaptcha in Spring MVC web application. The application consists in a form to register a new user. This form contains a captcha for avoiding a bot starts a massive registration attack.

First step is open an account to reCaptcha site (you can use your google account or create a new one).

Once you have entered go to My Account - Add New Site.

Then at domain box you should write the domain which will contain captcha validation. For this example I have entered localhost and I have checked Enable this key on all domains (global key). Of course information provided here is for testing porpoise and in production environment should be different. After you have registered your site, two keys are provided, private key (XXXX) and a public key (YYYY).

Before coding, let me show basic life-cycle of a reCAPTCHA challenge. Diagram is from reCaptcha web:

Second step is create a Spring MVC application, no secret here, I am going to explain only parts that are implied in reCaptcha integration. Apart from SpringMVC dependencies, recaptcha4j API should be added:

recaptcha4j.jar is an API that provides a simple way to place a captcha on your Java-based website. The library wraps the reCAPTCHA API.

Integrating reCaptcha into a form, requires two modifications:

One in client side, for connecting to reCaptcha server and get the challenge.
Second one in server-side for connecting to reCaptcha server to send the user's answer, and give back a response.

Client side:

For client side a tagfile has been created to encapsulate all logic of reCaptcha API in a single point, so can be reused in all JSP forms.

reCaptcha class requires the private key (XXXX) and the public key (YYYY) provided by reCaptcha in step one. The method createRecaptchaHtml(...) creates a piece of html code to show the challenge. In fact it generates something like:

And finally a JSP page with a form and captcha information:

See that form is generated as usual using Spring MVC taglib, but also we are using created tagfile (<tags:captcha>) for embedding captcha into form.

Server Side:

Server side is even simpler than client side. When a captcha is created using createRecaptchaHtml, two form element fields are created, recaptcha_challenge_field that contains information about the challenge presented to user, and recaptcha_response_field that contains the user answer to the challenge.

Apart from these two parameters, recaptcha4j requires remote address too. ServletRequest interface has a method (getRemoteAddr()) for this porpoise.

reCaptcha object is injected using Spring. It is important to note that UserInfo (data entered by user in form) does not contain any information about captcha, it only contains "business" data. Using @RequestParam reCaptcha information is retrieved by Spring and can be used directly into reCaptcha object.

The other important part is isValid() method. This method simply checks if response of reCaptcha site is that user has been passed the challenge or not. Depending on result you should act consequently, if challenge is not passed returning to previous page is a good practice.

This bean definition is simply for instantiating reCaptcha class with your private key. Using @Autowire bean is injected into controller.

Step Three:

Last step is watch that created form shows the captcha image and controller redirects you to page depending on what you have entered into captcha text area.

Extra Step:

Now you have a basic notion of how to work with reCaptcha, next step (out of scope of this post) is instead of showing again form without any error message, you could use BindingResult in Controller for notifying to user an error message:

result variable is an attribute passed to submitForm of type BindingResult. Of course JSP should be changed with <form:errors path="captcha"/> for showing the error message.

Another improvement is creating a HandlerInterceptor for validating forms with captchas. For example ReCaptchaHandlerInterceptorAdapter would contain reCaptcha management. preHandle method would return true if captcha challenge is resolved correctly by user (allowing defined controller do its work), or false and redirecting to an error page.

With previous handler configuration all forms would have captcha validation.

Hope you find useful this post, and now you can start protecting your web forms from spam or bots.

Download Eclipse Project.

Music: http://www.youtube.com/watch?v=XOykCYDMKBs

This Is a Flash Of Pure Inspiration, Més I Més I Messi, Però Més Però Molt Més (The Feet Continue To Dance - The Wizard Of Ox)

2011-05-22T12:30:00.000+02:00

Git is a distributed revision control system, where every working directory is a full-fledged repository with complete history and full revision tracking capabilities.

Git is categorized as DVCS (Distributed Version Control System), because is not dependant on a central server. So the academic way for working with Git is pushing/pulling data from/to each developer repository. This works in small teams or in a highly distributed development (open source projects that people are working around the world), but in mid-size teams or business companies, that require a central repository because of infrastructure/workflow process like Continuous Integration System, QA Checks before delivering, Environment Backups, External Manual Audits... seem that a traditional SCM should be desired. But this claim is far from reality, Git is still your VCS; how about creating a theoretical central repository? I say theoretical because in Git there is no central repository at a technical level. This repository will act as central because of convention. I call, and in many other posts also call this repository origin.

A Git remote repository is a repository without working directory. Only composed by .git project directory and nothing else.

Nvie has created a nice schema of this topology:

See that each developer pulls and pushes to origin, but also may exchange data with other peers. For example, if two or more developers are working on a new feature, they can push changes between them before pushing stable version to origin repository.

Git is not tied to any particular transmission protocol, it supports transmitting changes via USB stick, email, ..., or traditional way like HTTP, FTP, SSH, ...

So although Git has broken the typical SCM hub architecture to peer-to-peer structure, we can still create (by convention) a central repository for uploading stable code. And let me write again, "This central repo is just another node in the peer not THE REPOSITORY".

What I am going to explain is how to install and configure this "central repo" in an Ubuntu Server.

We can say that Git only takes care of repository management and leaves transport operations to lower layers. A typical transport configuration for these central repos is using SSH protocol. So let's install and configure a SSH server. (if you have already installed skip to next step).

Install SSH Server:

$ sudo apt-get install openssh-server

after installed try:

$ ssh <username>@<servername>

Configure SSH Server:

In /etc/ssh/sshd_config configure to only use SSH Protocol 2:

Protocol 2

Next step is to install Git: (You can skip this step if you have already installed).

Install Git (not git-core package):

$ sudo apt-get install git

Then execute Git command to check that has been installed correctly.

Next step is creating a bare repository for the project. By convention, bare repository directories end with .git. So first thing to do is create a .git directory of project.

Creating a bare repository from existing repository:

$ git clone --bare my_project my_project.git

This command transforms the /my_project/.git to my_project.git.

Creating a new bare repository:

If you are starting a new project you can initialize it directly as bare repository using:

$ mkdir my_project.git

$ cd my_project.git

$ git --bare init

Now all structure is created and ready to be transferred. Case that initial project was started on developer computer you should copy this directory (using scp for example) to origin.

Then execute next command:

$ git init --bare --shared

This command will add propertly group read/write permissions.

And now it is time to clone created repository to developer computer, I assume that developer has already an account in server (for connecting using ssh). So go to developer computer (or open another terminal) and type next command:

$ git clone <username>@<servername>:/<directories>/my_project.git

If user has read permissions to my_project.git directory, repository will be downloaded to local computer. Write permissions are required for checking in changes.

And now I suppose you are thinking that it was so easy creating a remote repository, but now another problem arises. If your company is small you can manually create a new user into your server for each developer, it should be easy to manage, but if your company is bigger, then management of all users is hard. You must create an account for each one, and more important, they will have access to server shell using ssh (not only for uploading code) or ftp, ..., and this fact implies a problem with security, you should take care of what a user can do and what cannot do in his shell.

So arrived at this point, one can setup accounts for everyone, which is straightforward but can be cumbersome. Another way is using an LDAP or any other centralized system, but this is alien topic for this post.

A second method is to create an account called "git" on the server, and ask every user who will have access, to send its SSH public key, and add that key to the .ssh/authorized_keys file of "git" user. I am sure that this approach sounds you familiar (github way?). So let's explain this way:

First of all each user should send you its public key, (they can find in .ssh directory *.pub file), or simply create new, using ssh-keygen command. See this tutorial for learning how to generate both keys http://github.com/guides/providing-your-ssh-key.

Setting up Git server with user public keys:

First step is create a git user with .ssh directory.

#from server
$ sudo adduser git
$ su git
$ cd
$ mkdir .ssh

Next step is create authorized_keys file where all public keys will be stored:

For example:

#from server
$ cat id_dsa.user1.pub >> ~/.ssh/authorized_keys
$ cat id_dsa.user2.pub >> ~/.ssh/authorized_keys

And now each developer, with public key published in authorized_keys and private key in his own .ssh directory, has access to repository. Let's try, open another terminal (would be developer machine in real scenario) and try to clone existing repo from server:

#from developer computer
$ git clone git@<servername>:<directories>/my_project.git

After repository is cloned to developer computer, modifications can be made and pushed them.

And now you can say, "Ok, I don't have to create one account for each developer but I am still having a problem with security", each developer still has access to shell. Yes it is true, but you can easily restrict the "git" user to only doing Git activities with a limited shell called git-shell. Next step is specifying git-shell instead of bash for Git user, in /etc/passwd.

$ sudo vim /etc/passwd

and change

git:x:1000:1000::/home/git:/bin/sh

to

git:x:1000:1000::/home/git:/usr/bin/git-shell

Now your server is secured, only Git operations are allowed using "git" account with users that have sent their SSH public key.

You have your central remote repository configured and ready to be used; at this point you may consider install Git tools like gitweb, gitosis or gitolite, but in this post are off topic.

I hope you have found this post useful.

Music: http://www.youtube.com/watch?v=q2AemC0cwy0

To Seek Out New Life And New Civilizations, To Boldly Go Where No Man Has Gone Before (TNG Soundtrack - Star Trek)

2011-05-10T20:17:00.000+02:00

From Wikipedia: OAuth (Open Authentication) is an open standard for authentication. It allows users to share their private resources (e.g. photos, videos, contact lists) stored on one site with another site without having to hand out their credentials, typically username and password.

There are a lot of posts talking about OAuth from Client Side, for example how to connect to service providers like Twitter or Facebook, but there are less posts about OAuth but from Server Side, more specificaly how to implement an authentication mechanism using OAuth for protecting resources, and not for accessing them (Client Side Part).

In this post I will talk about how to protect your resources, using Spring Security (Spring Security OAuth). The example will be simple enough to understand the basics for implementing an OAuth service provider.

I have found this post that explains with a simple example, what OAuth is and how it works. I think it is a good starting point with OAuth http://hueniverse.com/2007/10/beginners-guide-to-oauth-part-ii-protocol-workflow/

Now it is time to start writing our service provider. First of all I will explain what our Service Provider will offer.

Imagine you are developing a website (called CV) where users will register and after that they will be able to upload their Curriculum Vitae. Now we are going to transform this website to a Service Provider where OAuth will be used for protecting resources (Curriculm Vitae of registered users). Imagine again that some companies have agreed with CV people that when they publish job vacances, users will have the possibility of uploading their curriculum directly from CV site to HR department instead of sending by email or copy & paste from document. As you can see here is where OAuth starts managing security between CV website and Company RH site.

In summary we have a Curriculum Vitae Service Provider (CV) with protected resource (document itself). Companies that offer users the possibility of acquiring directly their Curriculum Vitae from CV are the Consumers. So when a user visits company job vacancies (in our example called fooCompany) and wants to apply for a job, he only has to authorize FooCompany "Job Vacancies" website with permissions to download its Curriculum Vitae from CV site.

Because we will use Spring Security for OAuth authentication, first of all we are going to configure Spring Security into SpringMVC CV application. Nothing special here:

In web.xml file we define Security Filter:

And in root-context.xml we define protected resources and authentication manager. In this case In memory apporoach is used:

Next step, create an Spring Controller that returns the Curriculum Vitae of logged user:

This controller returns directly a String, instead a ModelView object. This String is sent directly as HttpServletResponse.

Now we have got a simple website that returns the Curriculum Vitae of logged user. If you try to access to /cvs resource, if you are not authenticated, Spring Security will show you a login page, and if you are already logged, your job experience will be returned. Works as any other website that are using Spring Security.

Next step is modifing this project for allowing external sites can access to protected resources using OAuth 2 authentication protocol.

In root-context.xml:

First bean, is an OAuth2ProviderTokenServices interface implementation with id tokenServices. The OAuth2ProviderTokenServices interface defines operations that are necessary to manage OAuth 2.0 tokens. These tokens should be stored for subsequent access token can reference it. For this example InMemory store is enough.

Next bean is <oauth:provider>. This tag is used to configure the OAuth 2.0 provider mechanism. And in this case three parameters are configured; the first one is a reference to a bean that defines the client details service, explained in next paragraph. The second one is token service for providing tokens, explained in previous paragraph, and the last one is the URL at which a request for authorization token will be serviced. This is the typically Authorize/Denny page where service provider asks to user if it permits the Consumer (in our case fooCompany) accessing to protected resources (its Curriculum Vitae).

Last bean is <oauth:client-details-service>. In this tag you define which clients you authorize to access to protected resources with previous authentication. In this case because CV company has agreed with foo company that they can connect to its Curriculum Vitae Service, a client is defined with id foo.

Now we have our application configured with OAuth. Last step is creating a controller for taking requests from /oauth/confirm_access URL.

This controller returns a ModelAndView object with client information and which page should be shown for granting permission to protected resources. This JSP page is called access_confirmation.jsp and the most important part is:

As you can see Spring Security OAuth provides helper classes for creating confirmation form and deny form. When the result is submitted, URL /cv/oauth/user/authorize (internally managed) is called, there OAuth decides if returns protected resource (String returned by loadCV() method) to caller or not depending on what option user has chosen.

And that's all about creating an OAuth 2 system using Spring Security OAuth. But I suppose you are wondering how to test it, so for the same price I will explain how to write the client part (Consumer) using Spring Security OAuth too.

Client application (called fooCompany) is also a SpringMVC web application with Spring Security.

Spring Security part will be ignored here.

The client application contains a home page (home.jsp) that has a link to Spring Controller that will be responsible to download Curriculum Vitae from CV site, and redirecting content to a view (show.jsp).

As you can see is a simple Controller that calls a Curriculum Vitae service. This service will be responsible to connect to CV website, and download required Curriculum Vitae. Of course it deals with OAuth communication protocol too.

Service looks:

The suggested method for accessing those resources is by using Rest. For this porpose Spring Security OAuth provides an extension of RestTemplate for dealing with OAuth protocol. This class (OAuth2RestTemplate) manages connection to required resources and also manages tokens, OAuth authorization protocol, ...

OAuth2RestTemplate is injected into CVService, and it is configured into root-context.xml:

See that OAuth2RestTemplate is created using an OAuth resource that contains all information about where to connect for authorizing access to protected resource, and in this case is CV website, see that we are referencing an external website, although in this example we are using localhost. Also service provider URL (http://localhost:8080/cvs/cv) is set, so RestTemplate can establish a connection to content provider, and in case that authorization process ends successful, retrieving requested information.

<oauth:resource> defines OAuth resources, in this case, the name of the client (remember that this value was configured in server side client details tag for granting access to OAuth protocol). Also userAuthorizationUri is defined. This is the URI to which the user will be redirected if the user is ever needed to authorize access to the resource (this is an internal URI managed by Spring Security OAuth). And finally accessTokenUri, the URI OAuth provider endpoint that provides the access token (internal URI too).

Also creating a consumer using Spring Security OAuth is simple enough.

Now I will explain the sequence of events that happens when a user wants to give access to foo company for retrieving its Curriculum Vitae.

First of all user connects to foo website, and click on post curriculum vitae link. Then getCV method from controller is called. This method calls cvService, that at the same time creates a connection to resource URI (CV) using OAuth2RestTemplate. And this class acts as a black box, from client side, you don't know exactly what this class will do but it returns your Curriculum Vitae stored in CV website. As you can imagine this class manages all workflow related to OAuth, like managing tokens, executing required URL redirections to get permissions, ... and if all steps are performed successful, stored Curriculum Vitae in CV site will be sent to foo company site.

And that's all steps required to allow your site to act as Service Provider using OAuth2 authorization protocol. Thanks of Spring Security folks, it is much easier that you may think at first.

Hope you find it useful.

Download ServerSide (CV)
Download ClientSide (fooCompany)

Are You Locked Up In A World That's Been Planned Out For You? Are You Feeling Like A Social Tool Without A Use? (She - Green Day)

2011-04-20T19:50:00.000+02:00

From JBehave site: JBehave is a framework for Behaviour-Driven Development (BDD). JBehave allows developers, QA and non-technical or business participants, to write stories in a plain text file with minimal restrictions about grammar. Then a POJO is created for executing created story. This POJO should have the typical BDD structure Given, When and Then.

From Springsource site: Spring Framework is a Java platform that provides comprehensive infrastructure support for developing Java applications. Spring handles the infrastructure so you can focus on your application.

From Selenium site: Selenium is a suite of tools to automate web app testing across many platforms.

We have three technologies JBehave for acceptance tests, Selenium for web application testing and Spring dealing with infrastructure. In this post I will talk about integrating JBehave with Selenium 2 and Spring.

For this example I have created a very simple web application using Spring MVC. I know that business logic is not accurate to the reality, but it is simple enough to illustrate how to integrate all these technologies together.

I have divided this post in three main subsections:

Integrating JBehave with Spring. There is no web application here, only business logic.
Integrating Spring MVC with Selenium 2. Only to show how easy is implementing automated tests with Selenium 2.
Integrating JBehave with Selenium 2. Web application used in previous example but instead of using only Selenium for automating testing, JBehave instructs to Selenium which steps should execute.

Application that I will use is a simple TraderService, (explained in JBehave page (http://jbehave.org/reference/stable/)). This TraderService generates Stocks, and if a Stock is traded below threshold, its alert status is OFF and if it is traded above, alert status is ON.

In this tutorial I assume that you have a basic idea of JBehave and Spring.

Integrating JBehave with Spring:

In this case no web GUI is used, we are going to use JBehave for writing acceptance tests of business logic.

Basic classes are:

TradingService, that defines a method for creating stocks. TradingServiceImpl is the implementation.
Stock, that contains stock information and logic about its status.
StockAlertStatus is Stock status Enum.

Acceptance test part:

First of all we should create a story. A story is where stakeholders, developers... should say what they want the application do, and which are the expected results for given parameters. In our case a story has been created for validating that alarm is OFF if trade value is under threshold, and ON otherwise.

The important parts of that file are: Scenario for describing what we are testing, all symbols between <> that are used as variables, and Examples that are values injected to previous "<>" variables. In this story file two examples are provided, so two executions will be produced, one for each row. As final note, Given, When, Then words should be placed at start and are reserved words, also more than one Given, When or Then could be used in each story.

Next step, create a class that transforms a story written in "natural language" to code. We could say that this class is equivalent of creating a junit class; In JBehave these classes are called Steps. Because we are integrating with Spring an annotation called Steps is created. This annotation extends from Component annotation so Spring component-scan can wire up step classes too.

And Steps annotation is used in TradingServiceSteps class.

In TradingServiceSteps is where all magic occurs. This class is responsible of transforming story file to an execution. Let's see:

@Steps because we want Spring creates automatically this bean. TradingService is the business logic we want to test, and is injected using Autowire annotation. And finally one method for each Given, When, Then. Explained quickly, when JBehave finds an @Given, it searches into loaded stories for a phrase starting with Given. After that checks if @Given string value matches the Given definition expressed in story file. If matches then inject the story parameters as method parameters, for example STK1 as string parameter, or 5 as double threshold parameter. Moreover, in this case because we are using Examples in our story file, @Named annotation for each parameter is required. The named parameters allow the parameters to be injected using the table row values with the corresponding header name. Each parameter is converted from String to required parameter type.

We have written stories, and how to execute them (TradingServiceSteps class). JBehave requires another class, that will be responsible of configurating it. Basically you should configure Step classes and story files location, and what kind of reports are generated.

In our case, because we are integrating JBehave with Spring, some information is provided using Spring Injection.

This class is where JBehave is configured and is responsible for running all stories. Let's examine the most important lines:

In line 1 we specify a JUnit runner for running JBehave stories with Spring.
In line 2 we are configuring JBehave with Enum parameter converter, see that StockAlertStatus is an enum, because it is not a primitive parameter, a converter should be provided. JBehave comes with some convertes, but we can implement ours too.
In line 3 the embedder that we will use. This is the standard embedder for JBehave. Embedder represents an entry point to all of JBehave's functionality that is embeddable into other launchers.
And finally with @UsingSpring we are providing two Spring files, one where step classes are defined, and the other one where JBehave is configured.

Configuration file is a standard Spring file injecting required JBehave parameters:

This is a generic configuration file, that I use in all projects. You configure the output, the classloader for Embedder and prefix for parameters

And finally a Spring context file where all step classes are defined. And you know what, thanks of Spring this is as simple as:

No magic, remember that each Step class has an @Steps annotation? Thanks of component-scan, you don't have to define each Step class in @UsingSteps annotation or using tags.

Now run previous class as JUnit, and reports with results are generated.

Integrating Spring MVC with Selenium 2

Selenium 2 is a suite of tools to automate web app testing across many platforms. In this case WebDriver approach has been used. WebDriver is an interface for automating tests in a programmatic way. Selenium provides several implementations depending on browser where tests are run.

For this example I have created an Spring MVC application, that are composed of two pages, one form where all stock information is provided and a page where status of inserted stock is showed. Of course Spring MVC controller for managing all information is also implemented.

Controller of this small application is:

showForm method is used for showing the form where user will write stock information. submitForm method is called when submit button is pushed, and creates an stock and send to showstatus page the status of stock.

StockForm is simply a class with three attributes (stock, threshold and tradeAt price). No secret here.

Form page is also so simply but I will show it because form information will be used for configuring Selenium:

Page for showing status:

WebDriver is used in JUnit test for automatizing a sequence of events. In this case, the sequence will create an stock below threshold and assert that response page shows that alert status is OFF.

Most important sections of previous JSP are:

JSP taglibs <form:input path=""/> like <form:input path="name"/> in form, and <div id="result">. These fields are important because they are used by Selenium for filling form and asserting showed status.

For example, in Selenium class:

WebElement name = driver.findElement(id("name")) returns a "reference" to <input id="name" type="text"> element and using sendKeys method, you are sending keyboard chars to that component.

WebElement element = driver.findElement(id("result")), returns a "reference" to div element and using
assertThat(element.getText(), is(StockAlertStatus.OFF.name())); getText method, none tag characters of element are returned.

Now running this test is as simple as running TraderIsAlertedSelenium class as a simple JUnit test class. When running this class a browser (Firefox in this case) will be opened, and all programmed interactions will be executed on your screen.

At this point we just have to join both previous parts, and integration between JBehave with Spring and Selenium will be reality.

Integrating JBehave with Selenium 2 and Spring

JBehave has a module called JBehave-Web, that is used for integrating JBehave with web pages. Base classes are WebDriverProvider and WebDriverPage. Both classes are used by JBehave for abstracting from browser, and also for providing common methods to test webpages. In this example I won't use jbehave-web for two reasons, first because Selenium 2 with WebDriver offers a level of abstraction that is enough for this example, and secondly because WebDriverPage is a class that implements some common funcionalities for testing, but it is abstract, I don't like using extension only for sharing common operations between classes, it is a bad practice (not discussed here), I prefer aggregation. So in this case I have preferred implementing my class for implementing common functionalities.

In this case abstraction from browser is acquired using WebDriver (Selenium) interface. Moreover all common operations are implemented into this class. The idea of this class is to be used in several projects and for that reason a better design should be desired, but for current example is enough.

Next group of classes are those that use PageUtils object. I have created one class for each page that Selenium should interact with. Acts as a facade to web.

For example class for dealing with page containing form to insert new stock is:

Three operations can be executed in this page, the first one is open the page. Because "insert a new stock" is accessed manually (in this case is the front page), an open method is provided with URL. Also a method for filling stock form and and another for submitting it are provided.

And finally a class that transforms an story written in "natural language" to code (also known as Steps class), this class would be the same used in first example (TradingServiceSteps) but adapted for dealing with web pages (using previous classes).

See that there is no differences between this class and the one created in first example, but using web page interfaces instead of business objects.

Next modified files are:

Story file:

that has been modified to use web terminology.

Spring file:

that injects into TradingServiceWebSteps required beans.

Configuration file used in first example is the same, and Spring file for configuring JBehave is the same too.

In summary I can definitely say that integrating JBehave with Selenium 2 and Spring is not a difficult task, compared with the benefits that lead us having an automated acceptance test platform. I wish you have found this post useful.

Download Full Code

Everywhere I'm Looking Now I'm Surrounded By Your Embrace Baby I Can See Your Halo You Know You Are My Saving Grace (Halo - Beyonce)

2011-04-15T18:52:00.001+02:00

Spring Security provides comprehensive security services for J2EE-based enterprise software applications.

There are two important concepts in application security.

Authentication is the process of establishing a principal is who they claim to be, generally that information comes in form of username/password.
Authorization refers to the process of deciding whether a user is allowed to perform an action within your application.

In Spring Security, and as summary, we can say that two classes are responsible of implementing each concept:

Main interface for Authentication is AuthenticationManager. The default implementation is ProviderManager. This rather than handling request itself, it delegates it to a list of AuthenticationProviders which each one tries to perform the authentication against its back-end with username and password provided. An example of providers is DaoAuthenticationProvider, LdapAuthenticationProvider...
Main interface for Authorization is AccessDecisionManager. Spring Security includes several AccessDecisionManager implementations that are based on voting. Three AccessDecisionManagers are provided: AffirmativeBase (grants access if any voter returns an affirmative response), ConsensusBased ("Consensus" here means majority-rule (ignoring abstains) rather than unanimous agreement (ignoring abstains)), and UnanimousBase (requires all voters to abstain or grant access). In fact voters are the most important concept of authorization process, because are the final responsible of granting or not access to a resource.

Imagine next problem, you have developed a website for an online television, where only during daylight programs are live broadcasted and recorded, and during night programs recorded during day are rebroadcasted. Because of bandwidth problem, only registered users with ROLE_USER can watch live programs, but the rest of the world (registered or not) can watch at night the programs recorded during the day.

There are many approaches for developing that requirement, but how about implementing a voter that votes affirmative when it is night and negative when it is day?

See that most important method is vote. This method receives the caller invoking method, the secured object and the configuration attributes associated with the method being invoked and only returns if it grants, if it denies or if it abstains access to resource. Because our requirements are as easy as comparing if it is day or night these attributes are not used.

And I suppose you are wondering, "Ok man so easy, but how I register this new voter to the AccessDecisionManagers object?". Well it is also easy, the only inconvenience is that namespaces does not provide this feature and beans should be configured as old-school spring security files.

At line 1 we are configuring the security to http calls as usually but instead of relying on default decision manager, we are referencing to an access decision defined below.

At line 5, an AffirmativeBased decision manager is created, with two voters, one that will grant access if user have required role (line 8) and another one that is NightVoter implemented above granting only access if it is night.

And finally Authentication Manager beans with inmemory approach.

I think is a clean solution of an authorization problem, and also shows how Spring Security can adapt to very different scenarios involving web security.

Download Example.

Another Shot Of Whiskey Can't Stop Looking At The Door Wishing You'd Come Sweeping In The Way You Did Before (Lady Antebellum - Need You Now)

2011-04-10T18:37:00.000+02:00

With new release of JDK 7, a lot of really useful features has been developed, some of them I have write off before in this blog (JSR 203 and JSR 166y). In this post I am going to talk about one new small enhancement. This new feature is the addition of java.util.Objects class. This class is similar to java.util.Arrays or java.util.Collections but for objects instead of arrays or collections.

This class offers nine methods grouped by four groups: equality, hashing, nullables, and toString. Let's examine all of them.

compare(T a, T b, Comparator c):int => Returns 0 if the arguments are identical and c.compare(a, b) otherwise. Consequently, if both arguments are null 0 is returned.
deepEquals(Object a, Object b):boolean => Returns true if the arguments are deeply equal to each other and false otherwise. Two null values are deeply equal. If both arguments are arrays, the algorithm in Arrays.deepEquals is used to determine equality. Otherwise, equality is determined by using the equals method of the first argument. This operation is useful if you want to compare two objects and you don't know exactly if Object is a "single" object or an array. This method manages this problem, and compares both instances correctly.
equals(Object a, Object b):boolean => Returns true if the arguments are equal to each other and false otherwise. Consequently, if both arguments are null, true is returned and if exactly one argument is null, false is returned. Otherwise, equality is determined by using the equals method of the first argument. And I suppose you are wondering "nice but I have an equals method in object class". Yes you are right but look next example:

If foo is null, a NullPointerException is thrown. One can argue that you should check for null input parameters, this is a simple example, but I am sure all of us sometimes we have received a NullPointerException in an equals.

But see that:

Not And a Half is showed instead of throwing a NullPointerException.

hash(Object... values):int => Generates a hash code for a sequence of input values. The hash code is generated as if all the input values were placed into an array, and that array were hashed by calling Arrays.hashCode(Object[]). This method is really useful in DTO objects. For example Hibernate "requires" that all objects implement equals and hashCode. It is typical that DTOs can contain lot of fields, take a look any of these classes how many lines of code can contain those hashCode methods. But see how simple is using this method:

hashCode(Object o):int => Returns the hash code of a non-null argument and 0 for a null argument.
requireNonNull(T obj):T => Checks that the specified object reference is not null. This method is designed primarily for doing parameter validation in methods and constructors. If obj variable is null a NullPointerException is thrown. Look next example:

I think it is a clean solution, avoid noise code, and it is more readable than if(foo == null) throw new NullPointerException();

requireNonNull(T obj, String message): T => Checks that the specified object reference is not null and throws a customized NullPointerException using message parameter, if it is.
toString(Object o): String => Returns the result of calling toString for a non-null argument and "null" for a null argument.
toString(Object o, String nullDefault): String => Returns the result of calling toString on the first argument if the first argument is not null and returns the second argument otherwise. I find this method so useful for logging porpoises. Sometimes you are going to log some information that null value has a meaning. For example without using this class, a log line could be:

But would be more readable:

I am sure java.util.Objects would not go down in history as the best new feature added in JDK 7, but honestly, I find it so useful and it will help me so much developing code even more readable. Enjoy it.

Come On Let's Twist Again Like We Did Last Summer Yea, Let's Twist Again Like We Did Last Year (Chubby Checker - Let's Twist Again)

2011-04-07T19:38:00.001+02:00

JPA 2 Criteria API allows criteria queries to be constructed in a strongly-typed manner, using meta-model objects to provide type safety. This is a useful feature because when a change occurs in database, for example a rename of a field, your queries will not compile, and you will see the problem in compilation time instead of running time.

Yes I have already talked about in my previous post http://alexsotob.blogspot.com/2011/01/deep-inside-you-cry-cry-cry-dont-let.html but there are an API that do the same as Criteria API, and is called QueryDSL. QueryDSL is a framework which enables the construction of type-safe SQL-like queries for multiple back-ends including JPA, JDO and SQL in Java. Working with QueryDSL and JPA is like working with HibernateMetamodel Generator because QueryDSL has an Annotation Processor that generates Meta-model information from JPA 2 annotated classes. So I suppose you are wondering, why I should use QueryDSL instead of JPA 2 Criteria API? In its site there are interesting posts about that http://source.mysema.com/forum/mvnforum/viewthread_thread,49.

What makes really different QueryDSL from JPA2 Criteria API, is that QueryDSL also works with JDBC applications. Yes you read it right, JDBC applications can take benefit from QueryDSL, and instead of creating queries as plain text, they can be constructed in a strongly-typed manner too.

Some of advantages of using QueryDSL in JDBC are:

Code Completion in IDE.
Almost no syntactically invalid queries allowed (type-safe on all levels).
Domain types and properties can be referenced safely (no Strings involved!).
Incremental query definition is easier.

If you visit its webpage you could see one example using QueryDSL with JPA, but also one for JDBC. What I am going to explain is how to use QueryDSL with Spring Jdbc Template. Most of us, when we develop a Spring application and want to use JDBC, we use JdbcTemplate class or one of its extensions. For that reason I will explain how I use JdbcTemplate with QueryDSL.

First of all I implement an extension of JdbcTemplate class. I have called QueryDSLJdbcTemplate. This class has a simple method called queryForList(SQLQuery sqlQuery, RowMapper rowMapper, Expression... expressions) and has three parameters, the first one is a SQLQuery object, this is the main class where you define the query you want to execute (like JPA 2 Criteria), the next one is a RowMapper object as most of JdbcTemplate methods use, and the third one is an array of Expressions; these expressions represents each database fields we want to return as result, like id, name, age, ....

Implementation of this method:

At line 4, we are attaching a connection to given SQLQuery.

At line 6, the query is executed, and result set is returned.

At line 10, the result set is transformed to a list of required objects, using RowMapper.

Next step is creating a query. In this example I will use an Employee class that have two attributes, an id and a name. The query is finding an employee by name. So EmployeeDAO looks like:

Using JPA you specify which database engine is used injecting Database dialect. In our case it is a JDBC application so we should configure SQLQuery object with database engine used, so QueryDSL generates query syntax correctly. This is done with line 1 and 2.

Line 4 is an auto-generated class, similar to classes generated by Hibernate Annotation Processor. It contains all meta-information of an entity.

Line 5 is the query construction. See that we are not creating an SQL string (SELECT * FROM Employee as emp WHERE emp.name=?), but we are creating in a programmatic way. Look this line qEmployee.name.eq(name) because if we change field name to fullName, our code will not compile (qEmployee.name attribute does not exist now) meanwhile SQL string approach will compile, but crashing in runtime.

Line 7 is a simple RowMapper, and there the parameter name is also not specified as string but as an object, where native queries were rs.getString("name") and if name does not exists an SQLExpcetion was thrown, now a compilation error would be thrown too.

After RowMapper definition, we are executing the find method. The last two attributes are the fields we are looking for. Between SQL query and QueryDSL expression you can identify the FROM clause in both and the WHERE clause in both, but not the * of SELECT. This is the place where this information is passed.

Last method is for extracting real column name to result set.

Of course this is a basic implementation, for example Dialect should be injected rather than created each time, EmployeeRowMapper could not be an inner class, and getParameterName should be in a Util class, but because of clarity, all this code has been implemented in the same class.

And I suppose you are still wondering what is QEmployee class. Employee class is a simple DTO object. QEmployee is where all meta-information of Employee class is stored. In JPA usually JPA Providers have an Annotation Provider that read annotated model classes and generates Meta-model classes. In JDBC, there are no annotated model classes, but an alternative mechanism is provided for generating these classes. QueryDSL provides an ANT-task, a Maven-Task, and a Plain API. I will show you plain API configuration and same values should be provided for ANT and Maven tasks.

You must specify as input parameters, a connection to database and which schema contains business model. And as output parameters, which package should be generated meta-model classes, and root source code directory. The best approach for generating these classes is using Maven, so before compile goal is executed, all meta-data model is generated.

And Spring Application Context class looks as simple as:

Now you can take all benefits from using DSL for queries in JDBC applications.

'Cos The Only Thing Misplaced Was Direction And I Found Direction There Is No Childhood's End (Childhoods End - Marillion)

2011-04-01T19:29:00.000+02:00

JSR 203 is a new specification implemented in JDK 7, and is about NIO 2.0. JSR 203 defines three points of improvement:

Filesystem interface.
Complete Socket-Channel Functionality.
Support for Asynchronous I/O.

In this post I will talk about filesystem interface, because there are new classes that implements some file functionalities that more often than not I had developed myself in projects. In summary we will take a look to Path class and Files class.

Path is "an object that may be used to locate a file in a file system. It will typically represent a system dependent file path". Well in common language a path is the route to a resource. More or less like old File class, in fact java.io.File has a new method toPath() that returns a Path instance.

Files class is an utility class that implements common file operations like creating, finding (you say finding? yes), deleting, reading contents ...

For me typical operations that are implemented in Files class are:

* Delete a file (/tmp/test/sec.txt)

Path file = Paths.get("/tmp/test", "sec.txt");
Files.delete(file);

Files.delete method deleates passed file path, and that's important because with not empty directory a DirectoryNotEmptyException is thrown.

And how about deleting a directory with contents? let me introduce another new concept. FileVisitor interface. Files class has a method for walking along all directories tree. This is useful if you wanted for example implements the tree *nix command (prints all directory structure for given root directory). But in my case I will implement a complete delete function (*nix equivalent command would be rm -Rf /tmp/test).

Previous code is equivalent to command rm -Rf /tmp/test. SimpleFileVisitor is an implementation of FileVisitor. It implements default behavior for all FileVisitor methods, and in this case we override visitFile for deleting files. After all files of current directory are visited postVisitDirectory method is called and current directory can be deleted safetly. See that the result in this case is CONTINUE (continuing walking through tree, but as you can imagine you have other options like SKIP_SIBLINGS, SKIP_SUBTREE or TERMINATE).

* Copy a File

Files class has three main methods for copying files. It is important to note that you can copy files and directories, however files inside the directory are not copied, so the new directory is emptied even when the original directory contains files.

Files.copy(source, target, REPLACE_EXISTING);

Moreover two methods are also present for copying files. Files.copy(InputStream, Path, CopyOptions...) and Files.copy(Path, OutputStream). As you can imagine first method takes an inputstream and copy its content into given Path, and the second one, reads given Path and sends file content to passed outputstream.

Same is applied for Files.move(Path, Path, CopyOption...).

For copying all directory structure with their files, a FileVisitor could be implemented as in previous example.

* Manage Metadata Information

Two main classes are created for managing files metadata. One class for reading metadata attributes like permissions, is hidden, is read-only, owner, modified-time, ... Because each OS manages file attributes in different manner, an implementation of that class are provided for each OS. For example there is an implementation for DOS systems, another one for POSIX systems, or even a helper class for implemting yourself attributes reader.

Posix example for printing group which belongs given Path:

The other class is FileStore. A FileStore represents a storage pool, device, partition, volume, concrete file system or other implementation specific means of file storage. This class is used for calculating disk usage.

* Reading, Writing, Random Access

Files class has methods for creating inputstreams, outputstream, readers, channels, ... because this features are not new I won't explain extensively. For example for acquiring an InputStream instance Files.newInputStream, Files.newOutputStream, ...

* Symbolic and Hard Link

With NIO 2.0 you can create a symbolic link http://en.wikipedia.org/wiki/Symbolic_link or a hard link http://en.wikipedia.org/wiki/Hard_link from a path.

Creating a symbolic link to a directory:

Creating a hard link to a file:

* Finding Files

Sometimes my programs should find all files with extension xml contained in a directory and manage them (for example create a zip with them). Before java NIO 2, a FileFilter was created and then create a matcher for only selecting those with xml extension. Now PathMatcher class can be used instead of creating yourself matcher. This matcher accepts Glob Syntax http://en.wikipedia.org/wiki/Glob_(programming) or Regular Expression. Glob syntax is easy to use and flexible and most of us have been used (in console operations) although we didn't know it was Glob Syntax.

Let's implement the next *nix script ls -R *.html in java.

As you can see this implementation of FileVisitor follows all directories structure finding all html files. See that there are two important lines:

matcher = FileSystems.getDefault().getPathMatcher("glob:*.html");

where we are creating a matcher that only returns true if file ends with html.

if (name != null && matcher.matches(name))

that returns true if current file matches the the glob condition.

Thanks of FileVisitor and PathMatcher this routine can be reused for any kind of files (modifying glob expression). Think now if you should do the same with java.io.File class, you would create a FileFilter where if you wanted to create a flexible solution you should create a Pattern Matcher, iterate over matches, and deal with recursive navigation through directory tree. See with PathMatcher how easy is changing between selecting all files ending with html extension to selecting all files starting with word 'Test'.

* Watcher Service

This new feature is really useful for receiving events when a directory has been changed by creation, modification or deletion of a file. Before NIO 2.0 you should create an "infinite-loop" that was watching if a new file was created. And this was done listening all files and comparing modification date or comparing with previous loop execution. Now this service automatizes all logic, and simply throws an event when registered change occurs.

Two final notes, first is that events are only thrown for files not for directories, and second one, watch service is not recursive, so it will only throws an event in case of files created into /tmp not /tmp/my-directory. As with all java NIO 2.0 you have FileVisitor interface for dealing with recursive directory tree.

* Determine MIME Type

If your application requires to know MIME type, Files class has a probeContentType. The implementation of this method is highly platform specific and is not infallible.

Path path = Paths.get("/tmp/dataset.xml"); System.out.println(Files.probeContentType(path));

It returns text/xml.

And those are all new features of NIO 2 that have changed my developer life when I have to develop an application where managing files are required. I wish you find them as usually as I do.

Teo Torriate Konomama Iko Aisuruhito Yo Shizukana Yoi Ni Hikario Tomoshi Itoshiki Oshieo Idaki

2011-03-31T19:17:00.000+02:00




This week I have reached 10K visits. I would like to say thank you to everyone who have read this blog.

Also I would like to dedicate to Japanese people, and all heroes of Fukushima, without them the disaster could have been worse. 

I wish I will reach 25K visits as soon as possible and I could explain it with better news.




Alex.

A Te Che Sei Il Mio Grande Amore Ed Mio Amore Grande

2011-03-27T20:04:00.001+02:00

Maven Verifier Plugin, is a Maven Plugin that is used for verifying the existence of certain conditions into files content. These conditions are expressed in form of regular expression, so if regular expression is matched in defined resources content, no error is showed, if not, build fails and error message is shown indicating which file does not matches the given expression.

Why I find this plugin useful? Usually my projects have three execution environments, one for unit testing, another for integration/acceptance test and production one. As you can imagine, each one has its configuration, like database configuration. Each environment has a different database, for example unit testing has a HSQL engine, while integration and production have a PostgreSQL. For dealing with that problem I usually create three different Spring files, each one loading required properties, and depending on environment, the applicationContext is modified for importing required resources. Let's look another example, in my work, I develop planners for instruments, in integration tests, an emulator is used, while in acceptance tests and production, as you can imagine we are using a real instrument. For that reason, we must inject into our business objects, which driver to use (emulator driver or real driver), and as you can imagine two spring files are created and are imported into application context depending on the stage of building.

The problem with changing importing files in applicationContext depending on environment, resides that implies a manual human process, and because it is human, an error can occurs and delivery a version with incorrect configured application context. Meanwhile Spring Framework 3.1 is not released as stable version (Spring Profiles would resolve that problem), Maven Verifier Plugin can help us to avoid that problem.

In our Continuous Integration System, one of our steps before releasing a version is check that all configuration files are configured with correct values, keep in mind that I have showed only two examples, but some other values are changed between development environment and production environment, like time constants, file locations, log level ... Thanks of that plugin this checking procedure is executed automatically.

Let's see an example:

First of all pom.xml must be configured for using Maven Verifier Plugin:

<verificationFile&gt; tag is where you configure which files should be verified and which rules should be applied.

And verifications-rules.xml:

In this example we are verifying that property-placeholder defined in applicationContext.xml are loading properties from META-INF/spring and not from any other location. Same approach can be used for verifying injected beans, constants, log level ... case that any verification does not matches, the build result would be a fail.

Although I always though myself "hey men this could not happen to me", one day, and you don't know whyhappens, and you upload code not correctly configured, and when VVT department starts verifications, project starts to crash, and then all test protocol should be cancelled, you must change one line, upload one line change to repository, re-deploy all application, and start again.

Since that day, I always create a regular expression for assuring that when my code is deployed for production, all configuration files contains correct values.

When Spring Framework 3.1 sees the light all will be different, meanwhile and for legacy code, try Maven Verifier Plugin.