8.7 Portlet caching

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.

Example 8-19 Portlet caching in the portlet.xml 

<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 portlet.xml, the portlet may programmatically change the expiration time. The request property expiration-cache should be used to modify the caching values.

Example 8-20 Programmatically changing the expiration time-out value 

RenderResponse.setProperty(
    PortletResponse.EXPIRATION_CACHE,
    (new Integer(600)).toString() );

While the portlet content is cached and the portlet is not a target of a request, the cached content will be used during the render phase. If there is a request for the portlet, the cached content will be disregarded and the render method of the portlet will be invoked.

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