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Jan K. Labanowski: "Tomcat, servlets, JSPs and other friends"

Application Server

Application server is an application which processes specific types of requests and runs perpetually as a daemon/service. It accepts requests from Web server via some communication protocol, and returns results back to the Web server. It is always up, and does not need to be started for each request. Application server does not have to run on the same computer as Web server. Moreover, there maybe many application servers running in parallel, and the load can be spread between them evenly (how do you think Search Engines run?).

For the  Web Server<-> Application Server  combo to work together, they need a communication protocol. The underlying technology used is usually TCP/IP (i.e., the Web Server and Application Server may, but need not be, on the same computer). In the communication protocol, the Web server is usually a client of the Application Server, since it is the Application Server which waits for the requests from Web Server, and returns results to the Web server. The specialized piece of Web server, which talks to Application server is usually called a  connector module .

The typical log of events looks like:

  • Web server receives the request for dynamic content from the Web browser.
  • Request is reorganized and packaged in a specific format (one required by the communication protocol) and given to the connector module of Web server.
  • Connector module sends the request to Application server and waits for the response.
  • Connector module receives response from the Application server and passes it back to Web server.
  • Web server resturns the response to Web browser which originated the request

 

Modified: Tue Feb 12 20:34:06 2002 GMT
Page accessed 2289 times since Tue Feb 4 15:14:06 2003 GMT