GateIn Portal interface is fully customizable using applications called portlets. The Portlet API is described in JSR-286.

There are several technologies available for writing portlets. The most basic one is directly implementing the plain JSR-286 portlet interface. Alternatively, by means of JBoss Portlet Bridge, you can also use JavaServer Faces (JSF) and RichFaces for portlet development.

Whichever technology you choose, please refer to Starting a Portlet Project to learn how to set up your project in a robust and effective way using GateIn Portal Bill of Materials (BOM).