Packaging

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Packaging

A J2EE application is delivered in an Enterprise Archive (EAR) file. An EAR file is a standard Java Archive (JAR) file with an .ear extension. The EAR file contains J2EE modules. Using EAR files and modules makes it possible to assemble a number of different J2EE applications using some of the same components. No extra coding is needed; it is just a matter of assembling various J2EE modules into J2EE EAR files.

A J2EE module consists of one or more J2EE components for the same container type and one component deployment descriptor of that type. A deployment descriptor is an XML document with an .xml extension that describes a component's deployment settings. An enterprise bean module deployment descriptor, for example, declares transaction attributes and security authorizations for an enterprise bean. Because deployment descriptor information is declarative, it can be changed without modifying the bean source code. At run time, the J2EE server reads the deployment descriptor and acts upon the component accordingly. A J2EE module without an application deployment descriptor can be deployed as a stand-alone module. The four types of J2EE modules are:

Enterprise JavaBeans modules contain class files for enterprise beans and an EJB deployment descriptor. EJB modules are packaged as JAR files with a .jar extension.

Web modules contain JSP files, class files for servlets, GIF and HTML files, and a Web deployment descriptor. Web modules are packaged as JAR files with a .war (Web ARchive) extension.

Resource adapter modules contain all Java interfaces, classes, native libraries, and other documentation, along with the resource adapter deployment descriptor. Together, these implement the Connector architecture (see J2EE Connector Architecture) for a particular EIS. Resource adapter modules are packages as JAR files with a .rar (Resource adapter ARchive) extension.

Application client modules contain class files and an application client deployment descriptor. Application client modules are packaged as JAR files with a .jar extension.

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All of the material in The J2EE Tutorial for the Sun ONE Platform is copyright-protected and may not be published in other works without express written permission from Sun Microsystems.