Explain the architecture of the application flow in WAS Environments?

The basic flow of the application starts when the user’s request to a URL.The URL is a combination of the Hostname, port no and context root of the specific application. The URL has a valid hostname/IPAddress of the application installed machine.

In most general, A HTTP Server/Webserver can handle the HTTP requests. Webserver maintains and serve the static pages to the users and for dynamic pages it will direct the requests to the Application Server.

The Webserver plug-in uses a XML configuration file to determine whether a request is for WAS and identifies the request as addressing a Java servlet and utilizes its configuration data to pass the request on to the servlet runtime engine code. The appropriate servlet is invoked via HTTP.

Next, the servlet understands which method or call it needs to make to obtain the information to satisfy the client request.

The third step involves business logic written as part of the Enterprise JavaBeans, which connects to the back-tier database and performs the transaction.

When the query results are sent back to the WebSphere middle-tier environment, the Java servlet regains control and manages the response page generation which needs to be served back to the client making the original request. To do that, an appropriate Java Server Page can be selected to help generate the dynamic content. The computed Web page with the results of the query is then served back to the Web client via the HTTP server.