How WebSphere Application Server plug-in works

This article for beginners who don't know about WebSphere plug-in. We know plug-in forwards the HTTP requests from web server to application server. It is plug-in primary work. Now, Look about how the plug-in works. Mainly plug-in work is divided into 4 operations.

                     

1)Initialization

2)URL matching and server determination

3)Sending the request to the application server

4) receiving the response from application server.

Before discussion of these operations, we must know how the web server will send the request to the plug-in.

The Web server gives  an opportunity to handle every request to WebSphere plug-in first, Then ,if WebSphere plug-in is not configured to serve that URL(request), Then the request go to the Web server for servicing.(This is the primary work of web server).

1)Initialization:

If we configure web server and plug-in, 2 lines are added In httpd.conf file of web server.

1)LoadModule ibm_app_server_http_module/bin/mod_ibm_app_server_http.dll

2)WebSpherePluginConfig \config\cells\plugin-cfg.xml

Here LoadModule points to the plug-in DLL, and WebSpherePluginConfig points to the plugin-cfg.xml file, which lists all the URLs that are to be serviced by the WebSphere cell.

When web server is starting, the plug-in DLL will be loaded in  web server process, then It loads "plugin-cfg.xml" into plug-in process.

check the "plugin-cfg.xml" file(i.e. parsing) and validates plug-in configuration file. After this work, plug-in is ready for receiving http requests.

2)URL matching and server determination:

Based on WebSphere plug-in configuration, the plug-in will match the URL and send the request to application server. This redirection is based on a set of rules dependent upon the WebSphere Application Server configuration.

3)Sending the request to the application server:

Here plug-in will do 2 steps

1)Once server is determined. the plug-in add one http client object with data from the user request. Once this new HTTP client object has been populated, it is ready to be sent.

2)The request is sent.

4. Receiving response from the application server:

After sending a request to the application server, the plug-in goes into a wait state (waiting for the response). The end of this wait state can be reached in the

following ways:

1) Expected behaviour (If everything is fine).

2) Unexpected behaviour (U know about it. We don't like it. but it will happen).