ear, jar and war are standard application deployment archive files. As they are considered standard therefore any kind of application server is well aware that how to deploy or unpack them.
An EAR file (standard JAR file) has an “.ear” extension, which is also known as Enterprise Archive file. J2EE application along with its modules is delivered into EAR file. Other JAR files couldn’t be present in JAR files. However, WAR and EAR files possess JAR files. An EAR file has all WARs and
Updated 01-15-2012 at 08:32 AM by J2EE
If you writing J2EE applications, you need to deploy your application to J2EE container like JBOSS. I will shed some light on how to write simple deployment descriptors for your web applications.
I am deploying my JSP application on JBOSS. For JBOSS, we need to put our application in WAR format in deploy folder. So deployment descriptor will have following 2 tasks: Archieve the application into WARCopy that WAR to deploy folder of JBOSS