EJB Tutorial for Beginners – Learn EJB and (Enterprise Java Bean) Framework in simple and easy steps starting from basic to advanced concepts with. This topic provides a high-level overview of the distributed component architecture defined in the Sun Microsystems Enterprise JavaBeans (EJB) version 2.x. To start, take a look at the EJB3 SLSB nce21_bean. Stateless3Bean, the EJB SLSB nce21_bean.
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The complete Turorial JavaBeans specifications and descriptions of the technology are available from the java. Enterprise beans provide several benefits for application developers. They do the following: Allow you to build distributed applications by combining components developed using tools from different vendors.
Make it easy to write applications. You do not have to deal with low-level details of transaction and state management, multithreading, resource pooling, and other complex low-level APIs.
However, if necessary, expert programmers can still gain direct access to the low-level APIs. Are developed once and then deployed on multiple platforms without recompilation or source code modification.
This also provides for interoperability between enterprise beans and non-Java applications.
Enterprise beans An enterprise bean is a non-visual component of a distributed, transaction-oriented enterprise application. You can customize them by changing their deployment descriptors and you ejb assemble them with other beans to create new applications.
There are three types of enterprise beans: Session beans and message-driven beans are coarse-grained components designed to model business process while entity beans are used to model fine-grained data objects. Session beans are non-persistent enterprise beans. They can be stateful or stateless.
Act on behalf of a single client and maintain client-specific session information called conversational state across multiple method calls and transactions. Do not maintain any conversational state and are pooled by their container to handle multiple gutorial from multiple clients. Entity beans are enterprise beans that contain persistent data and that can be saved in various persistent data stores.
Each entity bean carries its own identity. Entity beans that manage their own persistence are called bean-managed persistence BMP entity beans.
Chapter Referencing EJB3 beans in EJB and vice versa
Entity beans that delegate their persistence to their EJB container are called container-managed persistence CMP entity beans.
Message-driven beans are enterprise beans that receive and process JMS messages. Tutoorial session or entity beans, message-driven beans have no interfaces.
They can be accessed only through messaging and they do not maintain any conversational state. Message-driven beans allow asynchronous communication between the queue and the listener, and provide separation between message processing and business logic.