EJB 3.0 Features
Elimination of Home and Remote Interfaces:
The new session beans contain all the business methods inside the business interface. The bean provider designates the business interface as local business interface or the remote business interface or both according to the client whether it is local or remote.
Elimination of Component Interface:
Component interface in EJB2.1 or in earlier versions are used to provide a way through which the container notifies the bean instances of various life cycles they are affecting it.
Now the next question that arises is that how a bean class get notified by the container if it is interested? The solution is that there are two ways to do so, the first one is, the bean provider can implement a separate bean class that consists of all the callback notification methods that inform the container to treat it as a listener class. The second way is that, a bean provider can implement the notification method inside the bean class and designate this method to handle the corresponding events In both the cases bean class uses annotations.
Simplified Access to Environment:
Almost all the EJBs are required to access the environment to gain access to external resources, enterprise beans and other entries like properties. To get hold of these entries EJB mainly relies on JNDI API. EJB 3.0 also includes the features like lookup method on the EJBContest and dependency injection to access the bean's dependencies.
Dependency Injection:
Dependency injection is the mechanism through which the container injects the requested environmental entry to make available to the bean instance before any bean instance is invoked on that particular instance. Then the container injects these entries into bean variables or methods. It is bean provider's duty to tell the container that which method or variables should be injected at runtime. The bean provider can do this by using the deployment descriptor or annotations. Bean methods used for dependency injection should follow the java naming convention for properties in that they should follow the setXXX() convention.
EJB Context:
Bean must know about its environment at runtime such as security principle, transaction context in which its method is invoked and so on. javax.ejb.EJBContext API works like a window for the bean to the outside world through which it is interacting to the container. EJBContext is further categorized into SessionContext and MessageDrivenContext for the session beans and message driven beans respectively. Bean instances may use the dependency injection to access EJBContext instance. Another way through which a JNDI accesses the environment variables is the lookup() method of the EJBContext interface. Bean must use the JNDI API
to access the environmental dependencies.
Simple JNDI lookup of EJB:
Lookup of the EJB has been simplified so that the client can directly invoke methods on EJB rather than creating the bean instance simply by invoking create method on EJB.
Interceptors: An intercept is a method used to intercept a business method invocation. Stateless session beans, Stateful session beans and message driven beans may includes the interceptors. We can also define an interceptor class instead of defining the interceptor methods in the bean class.
The new session beans contain all the business methods inside the business interface. The bean provider designates the business interface as local business interface or the remote business interface or both according to the client whether it is local or remote.
Elimination of Component Interface:
Component interface in EJB2.1 or in earlier versions are used to provide a way through which the container notifies the bean instances of various life cycles they are affecting it.
Now the next question that arises is that how a bean class get notified by the container if it is interested? The solution is that there are two ways to do so, the first one is, the bean provider can implement a separate bean class that consists of all the callback notification methods that inform the container to treat it as a listener class. The second way is that, a bean provider can implement the notification method inside the bean class and designate this method to handle the corresponding events In both the cases bean class uses annotations.
Simplified Access to Environment:
Almost all the EJBs are required to access the environment to gain access to external resources, enterprise beans and other entries like properties. To get hold of these entries EJB mainly relies on JNDI API. EJB 3.0 also includes the features like lookup method on the EJBContest and dependency injection to access the bean's dependencies.
Dependency Injection:
Dependency injection is the mechanism through which the container injects the requested environmental entry to make available to the bean instance before any bean instance is invoked on that particular instance. Then the container injects these entries into bean variables or methods. It is bean provider's duty to tell the container that which method or variables should be injected at runtime. The bean provider can do this by using the deployment descriptor or annotations. Bean methods used for dependency injection should follow the java naming convention for properties in that they should follow the setXXX() convention.
EJB Context:
Bean must know about its environment at runtime such as security principle, transaction context in which its method is invoked and so on. javax.ejb.EJBContext API works like a window for the bean to the outside world through which it is interacting to the container. EJBContext is further categorized into SessionContext and MessageDrivenContext for the session beans and message driven beans respectively. Bean instances may use the dependency injection to access EJBContext instance. Another way through which a JNDI accesses the environment variables is the lookup() method of the EJBContext interface. Bean must use the JNDI API
to access the environmental dependencies.
Simple JNDI lookup of EJB:
Lookup of the EJB has been simplified so that the client can directly invoke methods on EJB rather than creating the bean instance simply by invoking create method on EJB.
Interceptors: An intercept is a method used to intercept a business method invocation. Stateless session beans, Stateful session beans and message driven beans may includes the interceptors. We can also define an interceptor class instead of defining the interceptor methods in the bean class.
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