Creating a portlet from existing WAR file

I have an existing war file, nothing special about it, just a normal web application. I am making a portal page and I want to make this existing web application into a portlet. Anyone know how to go about doing that? Basically if I could just stick this war file into a portlet window, that would be great but I don't know where to begin.

I am using OpenPortal 2.x that has been installed on Tomcat 6.0.x and programming in Eclipse Helios.

Yes you can package your portlet wars in the specified format and ensure you have a portlet.xml in addition to the web.xml

I have not used OpenPortal but I assume it is the portal framework that allows you to deploy your individual portlet as a war.

A diagram example is available here. See 5.2.1.2. Package Structure for more.

Another thing you can do is to use this tutorial for OpenPortal and Eclipse, and create a sample portlet and export it as a war. Then compare the new war with your existing war, most likely you'll only need to add a couple of files - one of them being portlet.xml

Then deploy your modified war into the portal.

I've found some more samples for you, take a look at these - you can directly compare your existing war to the structure of these. Try deploying some of these, so you'll know if they work on OpenPortal too.