You can get a Thread Dump using the JMXConsole. Here is how to do it. However, this will only give you a full dump if you are using JDK 1.5. The JMX console method isn't applicable for AS7 since AS7 doesn't ship the jmx-console web application.
Others have reported success using a utility called SendSignal. The thread dump will be written to wrapper.log when using the JavaService Wrapper by Tanuki.