"The Java Portlet Specification (originally created through
JSR-168) provides a standard for developing portal components with
the Java programming language. Although the specification was
originally created with the intent of standardizing the API and
execution environment of portals and portlets, developers are also
leveraging the specification as a standard for developing Web
application plugins. By implementing or embedding a portlet
container within a Web application, developers allow their Web
applications to be extended by third parties through the deployment
of compliant portlets.
"Apache Pluto, the reference implementation of the Java Portlet
Specification, implements a portlet container that can be embedded
easily within a portal or Web application..."