JBoss.org Community Documentation
You can deploy several different types of enterprise applications in JBoss AS:
The WAR application archive (e.g., myapp.war) packages a Java EE web application in a JAR file. It contains servlet classes, view pages, libraries, and deployment descriptors such as web.xml, faces-config.xml, and jboss-web.xml etc.
The EAR application archive (e.g., myapp.ear) packages a Java EE enterprise application in a JAR file. It typically contains a WAR file for the web module, JAR files for EJB modules, as well as deployment descriptors such as application.xml and jboss-app.xml etc.
The SAR application archive (e.g., myservice.sar) packages a JBoss service in a JAR file. It is mostly used by JBoss internal services. Please see more in Chapter 3, The JBoss JMX Microkernel .
The *-ds.xml file defines connections to external databases. The data source can then be reused by all applications and services in JBoss AS via the internal JNDI.
You can deploy XML files with MBean service definitions. If you have the appropriate JAR files available in the deploy or lib directories, the MBeans specified in the XML files will be started. This is the way how you start many JBoss AS internal services, such as the JMS queues.
You can also deploy JAR files containing EJBs or other service objects directly in JBoss AS.
The WAR, EAR, and SAR deployment packages are really just JAR files with special XML deployment descriptors in directories like META-INF and WEB-INF. JBoss AS allows you to deploy those archives as expanded directories instead of JAR files. That allows you to make changes to web pages etc on the fly without re-deploying the entire application. If you do need to re-deploy the exploded directory without re-start the server, you can just "touch" the deployment descriptors (e.g., the WEB-INF/web.xml in a WAR and the META-INF/application.xml in an EAR) to update their timestamps.