How to tell if a response from WebSphere Application Server has been cached

An application that uses Dynacache servlet caching in the past had no indication in the servlet response if data came from the cache or not.

Starting with WAS version 7.0.0.11 in APAR PM01156,  Dynacache adds a header to the response that can be used to determine if the servlet response has been returned from Dynacache. The name of this header is "CACHED_RESPONSE"

An application may need to take different actions depending on  if the data has been cached.
The header CACHED_RESPONSE has been added to the header of the servlet response and set to true when the servlet output is obtained from the cache.