I am working on a Java Portlet (extending GenericPortlet), using JBoss 7.02 and LifeRay Portal 6.1.0 GA1. This is one of the bundles that can be downloaded from LifeRay's release archive.
During deployment, when the init() method is called, getRequestDispatcher() returns null. Below is the exact error message:
09:22:15,972 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/my-portlet-name]] (MSC service thread 1-15) Error during mapping: java.lang.NullPointerException
Below is a snippet from my init() method:
PortletConfig config = getPortletConfig();
PortletContext context = getPortletContext();
PortletRequestDispatcher normalView = context.getRequestDispatcher("/portlet.jsp");
As a temporary workaround, I have moved all getRequestDispatcher() calls to doView() where it executes without problem. I do not understand why getRequestDispatcher() can locate portlet.jsp when called during doView, but not when its called during init()
Am I missing a preceding call of some other method that would resolve this? Is this a known issue?
Thanks for any help.
Getting the request dispatcher in the doView is the only place I've seen it done. I would imagine that it returns null during init because there is no actual request to dispatch.
Typically the init method is used for time-expensive operations that you don't want to incur for each request. This might be something like reading data from a file, or creating a reusable SQL connection.
You should also keep in mind that you should keep any portlet state thread safe. Don't create class or object variables that can only be used for one request at a time. The portlet methods are not inhererently thread safe, so you need to make sure that whatever variables a request is interacting with won't be manipulated by another request that is executing concurrently.