This is sample manifest.mf file for my HelloWorldWeb module. The HelloWorldWeb.war wants to call methods inside the HelloWorldEJBClient.jar which is packaged in same .ear file as that of HelloWorldWeb.war. So in order for HelloWorldWeb.war classes to use methods in the HelloWorldEJBClient.jar it must add it in Class-path,
If you dont add the .jar file in the Class-path it will result in ClassNotFoundException at runtime.
Note that the MANIFEST can only list JAR files that are stored in the EAR file. Also even though a WAR file is an archive file it cannot be listed on any MANFIEST since the java artifacts within a WAR are only visible to the same WAR.