Caching improves performance by reducing the load on the server. Caching is per user per portlet, a portlet cached for one user will not be used for another user. A JSR 168 portlet must use the portlet.xml to enable caching.
<portlet> ... <expiration-cache>600</expiration-cache> ... </portlet>
The expiration cache is defined in seconds. In the example above, the contents of the portlet should be cached for 10 minutes. A value of zero indicates that the portlet caching is disabled. A -1 value will cause the portlet cache to never expire. Any value above 0 will be interpreted as the number of seconds the content should be cached for.
If the expiration-cache is defined in the ...