Java Archives (JAR) A JAR file encapsulates one or more Java classes, a manifest, and a descriptor. JAR files are the lowest level of archive. JAR files are used in J2EE for packaging EJBs and client-side Java Applications.<\/p>\n
A WAR (Web Archive) is a module that gets loaded into a Web container of a Java Application Server. A Java Application Server has two containers (runtime environments) – one is a Web container and the other is a EJB container.<\/p>\n
The Web container hosts Web applications based on JSP or the Servlets API – designed specifically for web request handling – so more of a request\/response style of distributed computing. A Web container requires the Web module to be packaged as a WAR file – that is a special JAR file with a web.xml file in the WEB-INF folder.<\/p>\n
An EJB container hosts Enterprise java beans based on the EJB API designed to provide extended business functionality such as declarative transactions, declarative method level security and multiprotocol support – so more of a RPC style of distributed computing. EJB containers require EJB modules to be packaged as JAR files – these have a ejb-jar.xml file in the META-INF folder.<\/p>\n
Enterprise applications may consist of one or more modules that can either be Web modules (packaged as a WAR file) or EJB modules (packaged as a JAR file) or both of them. Enterprise applications are packaged as EAR files – these are special JAR files containing an application.xml file in the META-INF folder.<\/p>\n
Basically EAR files are a superset containing WAR files and JAR files. Java Application Servers allow deployment of standalone web modules in a WAR file, though internally they create EAR files as a wrapper around WAR files. Standalone web containers such as Tomcat and Jetty do not support EAR files – these are not full fledged Application servers. Web applications in these containers are to be deployed as WAR files only.<\/p>\n
In application servers – EAR files contain configurations such as application security role mapping, EJB reference mapping and context root url mapping of web modules.<\/p>\n
Apart from Web modules and EJB modules EAR files can also contain connector modules packaged as RAR files and Client modules packaged as JAR files.<\/p>\n","protected":false},"excerpt":{"rendered":"
Java Archives (JAR) A JAR file encapsulates one or more Java classes, a manifest, and a descriptor. JAR files are the lowest level of archive. JAR files are used in J2EE for packaging EJBs and client-side Java Applications. A WAR (Web Archive) is a module that gets loaded into a Web container of a Java… Continue reading