If you’re needing to create a new JSR-286 portlet, the Apereo Foundation (formerly JASIG), have provided a Maven Archetype for the creation of a skeleton portlet.
Essentially you can run the following command:
mvn archetype:generate -DarchetypeGroupId=org.jasig.portlet.archetype -DarchetypeArtifactId=jsr286-archetype
It will ask you for the group, artefact and package information, and will automatically create a skeleton Spring MVC Portlet for you.
See the using the uMobile Portlet Archetype article for full details.