Portlet API (JSR-168) is what you need to look for. This will explain to you how views are managed by portlet container, how portlets are rendered and how actions are mapped.
Co
portlet interaction is always 2-phase - action and render - while web server interaction is always single phase;
in a standard Web application, the form is submitted to the servlet specified in action field of the html form tag. In JSR-168 portlet, the action URL for an HTML form is generated using the actionURL portlet tag e.g. <form action="<portlet:actionURL/>" method="post">
submitting the HTML form results in invoking the processAction(ActionRequest aRequest, ActionResponse aResponse) method of a portlet
servlets are allowed to do include, forward, and redirect; portlets are only allowed to include.
Servlets can render a complete page, portlets render only page fragments.
Portlet API (JSR-168) is what you need to look for. This will explain to you how views are managed by portlet container, how portlets are rendered and how actions are mapped.
Co
<form action="<portlet:actionURL/>" method="post">