Running code at application/class startup

It’s not rare the scenario where you end up needing to run some code during the initialization of a given class or of an application. This article will present a few options in how to achieve this task.

Run code when the class is loaded

In this scenario, you want to run some code when a given class is loaded by the JRE, but you want that code to be executed only once, regardless of the number of instances of that class. For this, you can use a static initialization block.

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CDI Producer

CDI (Context and dependency injection) is a great specification introduced in the JEE6 that offers a lot of resources. One of them is the Producer methods, and we’ll be talking about it in this post.

CDI Producer can be used in some scenarios, such as:

  • Making Non-CDI beans eligible to be injected into other CDI beans. You may be using some library that doesn’t expose their beans via CDI but you want to inject them in your CDI beans by convenience.
  • You have a bean that requires a constructor with some argument.

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Build an application from scratch: JEE 7, Java 8 and Wildfly

I have recently published a course called “Build an application from scratch: JEE 7, Java 8 and Wildfly” on Udemy. This course is all about using a lot of recent and important Java technologies and best practices of software development in order to create a complete enterprise application. Some of the technologies and tools covered are:

  • Java EE 7: JPA 2.1, Bean Validation 1.1, JMS 2.0, EJB 3.2, CDI 1.1, JAX-RS 2.0, security.
  • Java 8: Lambda expressions, Date and Time API, streams and more.
  • Libraries such as Gson, JUnit, Mockito and Hamcrest.
  • Arquillian for integration tests.
  • Wildfly 8 (former JBoss) as Application Server.
  • PostgreSQL for production and HSQLDB/H2 for unit and integration tests.
  • Maven.
  • Eclipse IDE (this is a Maven project, so you can use other IDE).
  • Postman Chrome extension to test all our REST endpoints.

If you are interested and want to know more details, you can check the course by clicking here. In this page, you can find more details about the course, watch some free videos.

If you have any questions, just let me know.

Understanding transaction attributes

In this post we’ll be talking about a subject that is little explored by most of the developers: Transaction attributes. When we’re creating a service (EJB, Spring..), we can either control the transaction manually (BMT – Bean Managed Transaction) or delegate this responsibility to the container (CMT – Container Managed Transaction). CMT is used in most of the cases and with declarative configuration and it’s for this type of configuration that the transaction attributes exist. They define, for example, if your method must or must not be invoked from within a transactional scope.

Just to make things easier and clearer, the term client in this post means the caller, that can be a standalone application, an EJB, a Spring Service, etc.

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Testing JEE6 applications with Arquillian

Creating automated tests for JEE applications has always been a challenge, once it requires a running container to provide all the services the application needs to work properly and that the tests need to be executed.

The Arquillian framework was born to make this job a lot easier to be executed. Your main goal is to provide a powerful test platform responsible of taking care of many aspects while testing JEE applications, such as start a container, deploy an application in the container, run the tests and stop the container. It also allows that your test classes can be enriched with annotations like @Inject, @EJB and @Resource, among others. This way, one can easily create real integration tests. Arquillian also allows users to choose either JUnit or TestNG to create and execute the tests, besides allowing the same test cases to be executed in different containers, such as JBoss, Glassfish and Tomcat.

This post’s goal is not to discuss the benefits in writing automated tests -TDD or not- but, instead, focus on how to use Arquillian through a practical example.

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JMS queues with JEE6 and JBoss 7

This post will show how to configure a JMS queue on JBoss 7.1.1-Final and how to make use of it through a JEE 6 application. Besides, some aspects regarding transactional session and JMS queue’s number of consumers will also be presented.


This post does not aim to depict JMS in details, but it will give an overview about it.
JMS is part of the Java EE specification and can be considered a MOM (Message Oriented Middleware) which allows clients to exchange asynchronous messages among them.
There are basically two models to exchange messages:

  • Queue: It’s a point-to-point on which one side (producer) pushes a message and places it in a JMS queue and the other side (consumer) pulls the message from the queue. This post will be using this model throughout its example.
  • Topic: Adopts the publish-subscribe model on which one side (publisher) pushes as message on a JSM topic and, for this topic, there can be 0 or more subscribers that receive all the published messages.

More details can be found on the JEE 6 Tutorial.

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