1. Write your own Valve. This will allow a lower-level analysis that not only sees more of the steering data, but also applies to all applications in Tomcat, not just one (and requires no mods to the apps). Before doing so, however, check the standard set of Tomcat valves. One of them might already do what you want.
2. Use a network sniffer. This will give you the truest picture, because it will allow you to monitor all traffic coming to/from Tomcat's ports and includes the network headers in the data count. It also means that you can get stats without mods to either the apps or Tomcat. However, being one step above the wire means that actual direct examination of the contents of the network packets is only possible for data that isn't being transmitted unencrypted.
Customer surveys are for companies who didn't pay proper attention to begin with.