25.3. Layouts

25.3.1. How to define a Layout

Layouts are used by the portal to produce the actual markup of a portal response. After all the portlets on a page have been rendered and have produced their markup fragments, the layout is responsible for aggregating all these pieces, mix them with some ingredients from the portal itself, and at the end write the response back to the requesting client.
Layouts can be either a JSP or a Servlet. The portal determines the layout to use via the configured properties of the portal, or the requested page. Both, portal and pages, can define the layout to use in order to render their content. In case both define a layout, the layout defined for the page will overwrite the one defined for the portal.
A Layout is defined in the layout descriptor named portal-layouts.xml. This descriptor must be part of the portal application, and is picked up by the layout deployer. If the layout deployer detects such a descriptor in a web application, it will parse the content and register the layouts with the layout service of the portal. Here is an example of such a descriptor file:
      <uri state="maximized">/industrial/maximized.jsp</uri>