J2EE Web Application 

A J2EE Web application may include Web components, static files (such as HTML pages, image files and so on), helper java classes, JavaBeans, or other components defined by the J2EE Specification. It also contains a Web deployment descriptor that contains configuration information, which is read at application deployment time. All these files are packaged in a Web application archive (WAR).

J2EE Web Application Structure

The J2EE platform defines that the J2EE Web applications use a standard hierarchical structure for storing their resources. This is the structure of the WAR file that represents the application prior to deployment.

The J2EE Engine Web Container extends this structure by adding a second deployment descriptor, referred to as an additional Web application deployment descriptor. It enables you to configure the specific behavior of the Web applications that are to be deployed on the J2EE Engine.

J2EE Web Application Structure

All application resources that are located in the WEB-INF directory cannot be served directly to the client.

If you have several Web applications that use one and the same library, you can deploy it separately and then just set references from your applications to the library. You set the references at application assembly and deployment time using the SAP NetWeaver Developer Studio, or later using the Visual Administrator tool.

Web Applications Life-cycle on the J2EE Engine

After you deploy a Web application on the J2EE Engine, it is immediately started by the Web Container on all server processes in the cluster.

The application has the status “started” even when a servlet (or JSP page) cannot be loaded. It will start as long as its deployment descriptors are parsed successfully.

You can also start an application when you do the following:

·        Use the START_APP shell command of the Deploy Service.

·        Start the Web Container Service.

·        Start the server process.

The application is stopped when:

·        You used the STOP_APP command of the Deploy Service.

·        You try to undeploy or update it. In this case, the Deploy Service first stops the application and then performs the update or undeploy activities.

·        The Web Container Service is stopped.

·        The server process, on which it ran, is shut down.

A running Web application is automatically restarted by the Web Container if you change its configuration information using the Runtime tab of the Web Container Service. For more information about the Runtime tab of this service, see Runtime Administration of Web Applications in the Administration Manual.