Documentum portlets use a single portlet class, com.documentum.web.env.jsr168.DocumentumComponent which extends javax.portlet.GenericPortlet. This class will launch the component that you specify for the portlet as the value of the view mode in the portlet.xml file and will also provide access to preferences and help for the component using the preferences and help mode values in the portlet.xml file.
If your IDE creates portlets by creating the portlet class, make sure you do not create a Documentum portlet within the IDE by specifying the portlet class as DocumentumComponent. The IDE will overwrite the Documentum portlet class and render all Documentum portlets invalid. If this happens, you can restore the portlet class from your installation WAR file.