Packaging EJB 3.0 Applications

The real success of Java EE applications lies in assembly and deployment, as this is the key to delivering on Java's promise of write once, run anywhere (WORA). If you fail to fully grasp this step, your application may not realize this level of portability.

A typical application has a handful of Java classes, and maintenance can be a nightmare if you are shipping your applications from one environment to another. To simplify maintenance you can create a Java archive (JAR) file. Typically, a JAR file is a file in zip format that contains classes. However, enterprise Java applications are packaged as specialized versions of JAR files—EAR, WAR, and EJB-JAR modules—before they can be deployed to a Java EE.compliant application server.

In this article we begin with a discussion of application packaging and deployment. The article also provides critical information on class loading, so that you can appreciate why the archives are packaged as they are. This is intended to provide you a better understanding of the packaging requirements for EJB that include entities. We explain the need for deployment descriptors, and look at how to use them. Finally, we look at a persistence unit and how to per form object-relational (O/R) mapping using XML. Read Full Article>>