Why not ejb3

Enterprise JavaBeans 3. The new specification leverages the annotations metadata facility introduced in Java 5, persistence and object-relational mapping best practices from tools such as Hibernate and TopLink, and the Dependency Injection pattern made popular by lightweight Java frameworks such as Spring.

This article discusses possible migration strategies for moving applications written using EJB 2. The possible migration paths are evaluated from both the perspectives of design and implementation.

This article does not intend to be exhaustive in illustrating the migration options. After reading this article, you should be able to choose the best option, within your own specific context, for migrating the legacy EJB code to the new specification.

This article assumes you are familiar with the enterprise bean, Java 5, and object-relational mapping features and concepts. To provide a context for this article's discussion of possible migration paths, I begin by discussing the changes in the new specification in the context of each of the different bean types and then at a generic level pertinent across multiple bean types.

In EJB 2. The bean implementation class itself was an EnterpriseBean type and, in the case of session beans, extended the SessionBean sub-interface. Callback method implementations in the bean class had to be provided so that the container could trigger them on occurrence of the appropriate lifecycle events.

In addition, critical elements of the bean, including its transaction and security definition, and whether it was stateful or stateless, were defined in the associated deployment descriptors. Listing 1 illustrates an example of a stateful session bean defined using the EJB 2. In the EJB 3. The home interface has been removed.

The business interface does not need to extend the EJBObject or the EJBLocalObject interface; instead, if required, it could be defined within the interface hierarchy that represents the business domain model.

It does not implement an EnterpriseBean type. The declaration and the configuration in the deployment descriptor can be defined within the Java code, using the annotations metadata facility. In addition, default values are provided for most configurations, thus minimizing the bean-specific configuration requirements.

Under the new specification, one could deploy session beans without any ejb-jar. In the case of EJB 3. Session beans that serve as Web service endpoints are annotated as a WebService.

Listing 2 illustrates the earlier example from Listing 1 of the stateful session bean using the EJB 3. The callback methods were implemented in the bean class and the container, on a particular event called the corresponding method. Message-driven beans never involved the concept of a home and a remote, or local, interface.

In EJB 3. The deployment descriptor can also be used to specify a bean as message-driven. Thus, it is not required for the bean class to implement the MessageDrivenBean interface. The business interface of a message-driven bean is the message listener interface that corresponds to the message type that the bean is a listener for.

In the case of Java Message Service, javax. MessageListener is the message listener interface or the business interface. The bean class needs to implement the message listener interface or annotate the message listener interface using the MessageDriven annotation.

This Ejb Container together with the Ejb Component act as a Framework with predefined functionalities. This relieves the programmer from coding certain areas like transaction, security and persistence that are provide by the Ejb Container itself. Like if a programmer is creating a bean related to processing a credit card he need not create coding for the Transaction and Security that is provided by the Ejb Container Automatically. We can use metadata annotations in our beans to specify what all services and functionalities we require.

These are added dynamically when required during deployment. Metadata annotations is a way to specify the properties in a POJO, and these functionalities get automatically added.

Ejb is a specification which is followed by a large group of user vendors creating application server. So all have to follow the same specification making our applications portable. DDD is the preferred way as compared to the traditional four tired architecture followed by Ejb 2.

Ease of use, Integrated solution stack— Ejb3 offers a complete stack of server solutions, including persistence, dependency injection, interceptors i. Your email address will not be published. Still to take proper use of the elephant power it had to be tamed, or Ejb2 was later simplified to Ejb3 Ejb3 is very simple having power and is serving the people very well like a cow giving milk to the universe. Overview of EJB Ejb is a platform for building ,reusable, portable and scalable business applications using java.

Ejb as Component Ejbs are server side components that you can use to build parts of an application like business logic or persistence code. Domain Driven Design DDD is the preferred way as compared to the traditional four tired architecture followed by Ejb 2. Ejb3 helps follow DDD. Beans created using Ejb3 JPA supports polymorphism, inheritance etc.