10.2.1 Dynamic Content Provider interface
A cacheable servlet or JSP file might contain a state in the response that does not belong to the fragment for that servlet or JSP. When the state changes, the cached servlet or JSP is not valid for caching.
Dynamic Content Provider (DCP) allows the developer to use its interface and add user exits to the servlet response object.
When the servlet response is generated, DCP is called to provide the output of the dynamic content of that fragment.