Validation Cache - Setting cache-control header

The portlet specification 2.0 has concept of Expiration Cache that allows you to make use of the Browser Cache to cache the response. The ValidationCacheSamplePortlet , demonstrates how to do that.

The Portlet Specification has introduced javax.portlet.CacheControl object that can be used to get granular control over the caching of the response. YOu can get object of CacheControl from either RenderResponse or ResourceResponse and call its method.

The ValidationCacheSamplePortlet portlet is very simple, all it does is that in the doView() method it forwards control to validation.jsp and in the validation.jsp it renders a button, which you click on that button it is making XHR call to the resource URL. Inside the serveResource method i am setting caching properties

public class ValidationCacheSamplePortlet extends GenericPortlet{
 protected void doView(RenderRequest request, RenderResponse response)
   throws PortletException, IOException {
  System.out.println("Entering ValidationCacheSamplePortlet.doView()");
  response.setContentType("text/html");
  getPortletContext().getRequestDispatcher("/validation.jsp").include(request, response);
  System.out.println("Exiting ValidationCacheSamplePortlet.doView()");
 }
 public void serveResource(ResourceRequest request, ResourceResponse response)
   throws PortletException, IOException {
  System.out.println("Entering ValidationCacheSamplePortlet.serveResource()");
  response.getCacheControl().setExpirationTime(600);
  response.getCacheControl().setPublicScope(true);
  response.setContentType("text/html");
  response.getWriter().println("Hello from  ValidationCacheSamplePortlet.serveResource " 
+ new Date());
  System.out.println("Exiting ValidationCacheSamplePortlet.serveResource()");
 }
}

In this sample code i am calling following two methods of CacheControl object in the
serveResource

1. setExpirationTime(600): This method will set cache-control equal to 600, which is equivalent of telling browser that cache this response for 600 seconds or 10 minutes and dont make request to server to get new response during next 5 min.


2. setPublicScope(true) This method is used for setting cache-control to public that means this response is not private to the user and its same for user A as well as user B, so even proxy can cache it. If you set this to false then that will tell proxy that this response is private and only browser can cache it

I tried deploying this portlet in WPS and accessing it through firefox and what i see is that portal is setting correct cache-control headers.



If you look at the Firefox cache then you will notice that the resource is cached for approx. 10 min. like this



Note: It seems that not all the portlet container support CacheControl and not uni-formally. Ex. This sample code to set cache-control header does not work in Pluto, it works in WebSphere Portal 6.1.5 in the serveResource() method but not in doView()