Logging Payload of POSTs to Tomcat

I've managed to enable access logging in Tomcat by editing the conf/server.xml and uncommenting the entry for the org.apache.catalina.valves.AccessLogValve Valve. I'd like to be able to dump the contents of POST's payload. It doesn't seem like any of the options in the pattern will do this. Is there a built in way to do this? Do I use the AccessLogValve?