Logging HttpServletRequests

Motivation

Whereas observing ServletResponses is non-trivial, Sun Oracle makes it much easier to observe HTTP requests via the ServletRequestListener interface. ServletRequestListeners are awesome; they make it super easy to record and log requests, thereby improving the undestandability of your web applications. Recording and logging ServletRequests with a listener is preferable to doing that same work in the requested resource (Servlet, JSP, etc.) since the former strategy achieves an improved separation of concerns.

Implementation

Big-Oh Software's CommonWeb Framework provides RequestObserverListener, an abstract implementation of the ServletRequestListener interface that can be extended to observe ServletRequests in myriad meaningful ways. That abstract implementation of the listener interface collaborates with the ObservedHttpServletRequest class, which adapts an original ServletRequest into an object that is more easily observed, recorded and logged.

An Example: Servlet Request Logging

Using the RequestObserverListener to log incoming Servlet requests is shamefully easy. Only a few lines of Java and XML are needed:

package foo.bar;

import net.big_oh.common.web.listener.request.*;

public class MyRequestLoggerListener extends RequestObserverListener
{

 @Override
 protected void doOnServletRequestInitialized(ObservedServletRequest observedServletRequest)
 {
  System.out.println(observedServletRequest);
 }

}

... and ...

<!-- web.xml snippet -->

<listener>
  <listener-class>foo.bar.RequestLoggerListener</listener-class>
</listener>

By applying the above logging listener to a web application, you'll see that new ServletRequests are logged in this format:
Received a HTTP/1.1 request from localhost (127.0.0.1) for resource http://127.0.0.1:8080/CommonWeb/ (GET) -- jSessionId: B46435C89F9FABCE571AF701E0BC6820 -- userName: unknown