weblogic-application.xml

Could you please let me know whether weblogic-application.xml can be added in a WAR file and if so, then how to do the same.

No, it cannot. If you do it, then it won't be considered.

It needs to be in an ear-file/META-INF

The weblogic-application.xml file is the WebLogic Server-specific deployment descriptor extension for the application.xml deployment descriptor from Sun Microsystems. This is where you configure features such as shared Java EE libraries referenced in the application and EJB caching.

This info is for WLS 10.3.x more details at:http://docs.oracle.com/cd/E21764_01/web.1111/e13706/app_xml.htm#i1007581

Maven

The weblogic-application.xml should be packaged in the META-INF directory of your final EAR (next to the standard application.xml).

With the Maven EAR Plugin, the default location for extra files to include in the EAR (that you can control with the earSourceDirectory parameter) is src/main/application. So the following would work (using the defaults):

myear
|-- src
|   `-- main
|       `-- application
|           `-- META-INF
|               `-- weblogic-application.xml
`-- pom.xml