Using Deployment Descriptors
Deployment descriptors are configuration files associated with projects and deployed with Java EE applications and modules. Deployment descriptors contain the declarative data required to deploy the components as well as the assembly instructions that describe how the components are composed into an application. Projects require different deployment descriptors depending on the technologies the project uses and on the type of the target application server. In addition to the standard Java EE deployment descriptors such as application.xml and web.xml, you can also have deployment descriptors that are specific to your target application server. For example, if you are deploying to Oracle WebLogic Server, you can also have weblogic.xml and weblogic-application.xml.
JDeveloper provides dialog boxes to inspect and set the properties of many deployment descriptors. You also can create and edit them as XML source files. The essential descriptors are created by the wizards that create deployment profiles. Add other descriptors only if you want to override default behavior. New deployment descriptors are placed in a META-INF subfolder of a project’s Application Sources or Web Contents folders.
Warning: Avoid creating any deployment descriptors that apply to EAR files for more than one project in an application or workspace. These files are assigned to projects, but have workspace scope. If multiple projects in an application or workspace have the same deployment descriptor, the one belonging to the launched project will supersede the others. This restriction applies to application.xml, weblogic-jdbc.xml, jazn-data.xml, and weblogic.xml.