- Entity Bean
An Entity Bean is a type of
Enterprise JavaBean , a server-side J2EE component, that represents persistent data maintained in adatabase . An entity bean can manage its own persistence (Bean managed persistence) or can delegate this function to itsEJB Container (Container managed persistence). An entity bean is identified by a primary key. If the container in which an entity bean is hosted crashes, the entity bean, its primary key, and any remote references survive the crash.In EJB 3.0, entity beans were superseded by the
Java Persistence API .Entity Beans before EJB 2.0 should not be used in great numberscite book |last=Monson-Haefel |first=Richard |authorlink= Richard Monson-Haefel|editor=Mike Loukides |others=Melanie Wang, Hanna Dyer |title=Enterprise JavaBeans, Second Edition |origyear=1999 |origmonth=June |edition=2nd edition |series=The Java Series |year=2000 |month=March |publisher=O'Reilly & Associates, Inc. |location=Sebastopol, CA |isbn=1-56592-869-5 |id=Library of Congress QA76.73.J38 M65 2000 |pages=p.44 |chapter=Chapter 2 |quote="When session beans are used to manage workflow, the number of connections that each client has to the server is substantially reduced, which improves the EJB server's performance"] because each entity bean was in fact a RMI stub with its own RMI connection to the EJB server. If you had to obtain 1000 entity beans for a single operation this would result in 1000 internet connections becoming used for the RMI back-end Fact|date=May 2008. Since TCP/IP only supports 65536 ports you are essentially limited to using 65536 entity beans at a time. For example, if a client application wanted to monitor the state of 1024 database entries it would take 1024 entity bean references and thus 1024 RMI connections to the EJB server, the EJB server would in turn need to support all 1024 connections from each client application, and would be limited to serving at most 64 client applications at which point all further internet connections would be ignored. These limitations are impossible to overcome when using entity beans over RMI.
References
External links
* [http://java.sun.com/j2ee/1.4/docs/tutorial/doc/EJBConcepts4.html What is an Entity Bean? (Sun's J2EE Tutorial)]
* [http://java.sun.com/j2ee/1.4/docs/tutorial/doc/EJBConcepts9.html Enterprise Beans lifecycle]
* [http://www.unix.org.ua/orelly/java-ent/ebeans/ch06_01.htm Life Cycle State Diagram of Entity Beans]
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