Application files

EJB application JAR files — An EJB application JAR file contains one or moreEJBs.
Web application WAR files — AWAR file contains a single Web application.Because an EAR file can contain multiple Web applications, each Web applicationin an EAR file must have a unique deployment context. The deploymentmechanism for EAR files allows just such a specification of different contexts.
Application client JAR files — The application client JAR file contains a single,standalone Java application that’s intended to run within an application clientcontainer. The application client JAR file contains a specialized deploymentdescriptor and is composed similarly to an EJB JAR file. The JAR file also containsthe classes required to run the standalone client as well as any clientlibraries needed to access JAAS, JAXP, JDBC, JMS, or an EJB client.
Resource adapter RAR files — The resource adapter RAR file contains Javaclasses and native libraries required to implement a Java Connector Architecture(JCA) resource adapter to an enterprise information system. Resource adaptersdon’t execute within a container; rather, they’re designed to execute as a bridgebetween an application server and an external enterprise information system.Each of these components is developed and packaged individually apart from the EARfile and its own deployment descriptor. A J2EE EAR file combines one or more of thesecomponents into a unified package with a custom deployment descriptor.Packaging Roles