Request Process Overview
The following steps describe the J2EE application flow:
1. A client application sends a request to access the J2EE application.
2. The request is received by the Web server which immediately passes the request to the Web server plug-in.
3. The Web server plug-in chooses a server to handle the request based on the resource being requested, identified by its Universal Resource Locator (URL), and forwards the request.
4. The WebSphere for z/OS daemon routes the request to the application control region based on the context root in the URL. (i.e. ibi_html or ibi_apps)
5. The control region checks that the request is authorized and places it on the Workload Manager (WLM) queue. If necessary, WLM starts a procedure that is used to start a new servant region address space in response to the queued request. WLM then passes the request to the servant.
6. Servant is the J2EE app server containing a JVM
It locates and loads the J2EE components from the configuration HFS and starts the applications.
7. Request is handed to Web container within the server, routing it to the proper servlet, based on request’s URL
a. Servlet class is loaded by the dynamic class loader.
b. The Java Naming and Directory Interface (JNDI) looks up data sources required by the servlet.
c. Data retrieved from one/many sources and returned to servlet.
d. Servlet sends output stream directly or sends data to JSPs.
o Response: HTML,XML, generated as a response
o Sent back through WebSphere plug-in to Web server.
8. If J2EE application component needs to access corporate data: uses connector (resource adapter) to communicate with the Enterprise Information System (EIS) such as CICS or IMS.
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