Introduction: EJB applications

Use this topic to explore the key concepts pertaining to Enterprise JavaBeans (EJB) applications. Based on the EJB specification, enterprise beans are managed Java components that typically implement the business logic of Java 2 Platform, Enterprise Edition (J2EE) applications, as well as access data.

Enterprise beans
An enterprise bean is a managed Java component that can be combined with other resources to create Java applications. There are three types of enterprise beans: entity beans, session beans, and message-driven beans. Enterprise beans focus on managing business logic, providing ways to compose business logic and declaring the transaction and security needs of business logic.
EJB modules
An EJB module is used to assemble one or more enterprise beans into a single deployable unit. An EJB module is stored in a standard Java archive (JAR) file.
EJB containers
An EJB container provides a run-time environment for enterprise beans within the application server. The container handles all aspects of an enterprise bean's operation within the application server and acts as an intermediary between the user-written business logic within the bean and the rest of the application server environment. Container-managed persistence (CMP) transfers data between the variables of an entity bean and a resource manager administered by the entity bean container.
Partial column updates for container managed persistence
Sequence grouping for container-managed persistence
After assembling an EJB module that contains CMP beans, you can prevent certain types of database-related exceptions from occurring during application run time. Using sequence grouping, you can specify the order in which entity beans update relational database tables.
Message-driven beans - automatic message retrieval
WebSphere Application Server supports the use of message-driven beans as asynchronous message consumers.
Message-driven beans - listener port components
The WebSphere Application Server support for message-driven beans deployed against listener ports is based on Java Message Service (JMS) message listeners and the message listener service, and builds on the base support for JMS.
Lightweight local operational mode for entity beans
WebSphere Application Server provides a special operational mode called lightweight local mode, which can improve the performance of entity bean methods. You can decide which entity beans in your application to run in this mode.
(CMP 2.x persistence only) Access intent policies
An access intent policy is a named set of properties (access intents) that governs data access for EJB persistence. You can assign policies to an entity bean and to individual methods on an entity bean's home, remote, or local interfaces during assembly. You can set access intents only within EJB Version 2.x-compliant modules for entity beans with CMP Version 2.x.
(CMP 2.x persistence only) Access intent service
Access intent is a WebSphere Application Server runtime service that enables you to more precisely manage an application's persistence.
Stateful session bean failover for the EJB container
WebSphere Application Server Version 6.0 enables you to construct applications with the assumption that your applications using stateful session beans are not limited by unexpected server failures. This version of the product utilizes the functions of the Data Replication Service (DRS) and Workload Management (WLM) so you can enable stateful session bean failover.



Related information
Learn about EJB applications
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Last updated: Aug 29, 2010 5:25:00 PM CDT
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