Tomcat: The Definitive Guide, 2nd Edition

Debugging with RequestDumperValve

Occasionally you will want to get a more verbose look at web traffic, much like the telnet and nc conversations detailed in the last section. Tomcat provides a tool for this very purpose: the RequestDumperValve. It is very easy to set up; just uncomment a line in server.xml, or add the line within any Host or Context:

<Valve
  className="org.apache.catalina.valves.RequestDumperValve"
/>

Once you restart Tomcat, you will get a very verbose output appearing in the log for the given Server, Host, or Context. To get an idea of how much information RequestDumperValve provides, Example 8-5 is a portion of a 106-line log for one hit on a web site (every line was preceded by a timestamp, which we've removed to save paper).

Each request begins with a line of equal signs, and a line of dashes separates the request and the response. This particular example was a request for /index.jsp.

Example 8-5. RequestDumperValve output for request to /darwinsys/

RequestDumperValve[/darwinsys]: =============================================================== RequestDumperValve[/darwinsys]: REQUEST URI =/darwinsys/index.jsp RequestDumperValve[/darwinsys]: authType=null RequestDumperValve[/darwinsys]: characterEncoding=null RequestDumperValve[/darwinsys]: contentLength=−1 RequestDumperValve[/darwinsys]: contentType=null RequestDumperValve[/darwinsys]: contextPath=/darwinsys RequestDumperValve[/darwinsys]: cookie=JSESSIONID=C04FE083F247D0C7F24174AA8B 78B526 RequestDumperValve[/darwinsys]: ...