2.5. Servlet Chaining and Filters

Now you've seen how an individual servlet can create content by generating a full page or by being used in a server-side include. Servlets can also cooperate to create content in a process called servlet chaining .

In many servers that support servlets, a request can be handled by a sequence of servlets. The request from the client browser is sent to the first servlet in the chain. The response from the last servlet in the chain is returned to the browser. In between, the output from each servlet is passed (piped) as input to the next servlet, so each servlet in the chain has the option to change or extend the content, as shown in Figure 2.9.^[6]

^[6] A web server could implement servlet chaining differently than described here. There is no reason the initial content must come from a servlet. It could come from a static file fetched with built-in server code or even from a CGI script. The Java Web Server does not have to make this distinction because all its requests are handled by servlets.