The simple portal framework, which builds on top of the portlet container, is JSR-286-compliant. However, the WebSphere® Application Server implementation supports a subset of the optional features in the JSR-286 Portlet Specification.
The aggregation tag library generates a portlet aggregation framework to address one or more portlets on one page If you write JavaServer Pages, you can aggregate multiple portlets on one page using the aggregation tag library. This tag library does not provide full featured portal aggregation implementation, but provides a good migration scenario if you already have aggregating servlets and JavaServer Pages and want to switch to portlets.
Preferences are set by portlets to store customized information. By default, the PortletServingServlet servlet stores the portlet preferences for each portlet window in a cookie. However, you can change the location to store them in either a session, an .xml file, or a database.
You can use either the events mechanism or the public render parameters mechanism to coordinate portlets within a portal.
A portlet only delivers fragment output whereas a servlet typically delivers document output. However, you can use the PortletServingServlet servlet, which is similar to the FileServingServlet servlet, to address portlets like servlets.