EJB 3.1 SPECIFICATION PDF DOWNLOAD!
Enterprise JavaBeans (EJB) is one of several Java APIs for modular construction of enterprise The EJB specification is a subset of the Java EE specification. (EJB ), JSR (EJB ), JSR (EJB ) and JSR (EJB ). The EJB specification is part of the Java™ Platform Enterprise Edition. EJB and EJB makes it much easier to develop EJBs, using annotations rather than. It is also telling that - even with all these new features - the EJB specification and all the backwards compatibility and additions that if offers.
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In this case, the asynchronous method will return a Future instance.
Concurrent access to the one and only bean instance can be controlled by the container Container-managed concurrency, CMC or by the ejb 3.1 specification itself Bean-managed concurrency, BMC. CMC can be tuned using the Lock annotation, that designates whether a read lock or a write lock will be used for a method call.
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Additionally, Singleton Session Beans can explicitly request to be instantiated when the EJB container starts up, using the Startup annotation. Examples Ejb 3.1 specification a global daily price list that will be the same for every user might be done with a singleton session bean, since this will prevent the application having to do the same query to a database over and over again Message driven beans[ edit ] Message Driven Beans  are business objects whose execution is triggered by messages instead of by method calls.
Java EE6: EJB3.1 Is a Compelling Evolution
It may subscribe to JMS message queues or message topics, which typically happens via the activationConfig attribute of the MessageDriven annotation. They were added in EJB to allow event-driven processing. Since session beans can also be synchronous or asynchronous, the prime difference between session- and message driven beans ejb 3.1 specification not the synchronicity, but the difference between object oriented method calling and messaging.
The level of indirection afforded by Java 5's annotations made the paradigm more powerful while requiring less of the developer. The willingness to forsake bad legacy decisions for different, new solutions, made the framework interesting to people who might have previously shunned EJB.
The handful or more of Java classes and interfaces required for your average bean in EJB 2.
New Features in EJB 3.1
Convention-over-configuration based defaults were put into place to make it ejb 3.1 specification straightforward to get up and running.
Its arrival isn't unwelcome, of course. It is also telling that - even with all these new features - the EJB 3. We will review some of these features in this post, and address their use.
New Features in EJB 3. Some increase the surface area of the user-facing APIs to introduce more flexibility. Some simply bring more flexibility. Singletons A singleton is a new type of session bean that provides one extra guarantee: There are many use cases that are better served with this feature: Please provide your plan here, and refer to the Spec Lead Guide for a more detailed description and a set of example ejb 3.1 specification you may wish to answer in your plan.
Ejb 3.1 specification Expert Group will publish early drafts for review by the community at convenient points during the development of the specification.
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Lock annotation and a javax. LockType type are used to specify the access level of the singleton's business methods or Timeout methods.
This prevents two clients from attempting to simultaneously change the state ejb 3.1 specification of ExampleSingletonBean. Other than the simplest solutions, all of them require the use of non-standard, third-party code.
The container is guaranteed to maintain a single shared instance of an EJB 3. This means that Singletons can cache state across the application tier.
Because it is an EJB, Singletons have all the middleware services you might expect--declarative transaction management, security, remoting, concurrency management, dependency injection, component life-cycle callbacks, interceptors and so on.