[Webwork-devel] JSR 162: Portlet API

[DeSouza, E. <ede...@ja...>]

For more info:
http://www.jcp.org/jsr/detail/162.jsp

The Portlet API specification defines an API for web application
components that interact with and can be aggregated in web applications
like portals. We refer to these components as portlets in the remainder
of this text.

Portlets are web components like servlets, but have additional, special
properties that allow them to easily plug into and run in enclosing web
applications like portals. Portlets are designed to be aggregatable in
the larger context of composite pages, e.g. multiple instances of the
same portlet parameterized with different per-user, per-instance portlet
data can coexist on the same portal page. Usually, many portlets are
invoked in the course of handling a single request to aggregate their
respective produced markup fragments in a page of markup. The markup
fragments generated by portlets often need to contain links to trigger
actions in the portlet, therefore URL-rewriting methods are required
that allow portlets to transparently create links within the markup
fragments they output, without needing to know how URLs are structured
in the particular web application.

Portlets rely on the portlet container infrastructure accessible via the
Portlet API for functions like access to user profile information for
the current user, access to the window object that represents the window
in which the portlet is displayed, participation in the portal window
and action event model, access to web client information, inter-portlet
messaging and a standard way of storing and retrieving
per-user/per-instance data persistently.

The Portlet API provides standard interfaces for the functions mentioned
above. The Portlet API extends the servlet programming model and defines
a common base class and interfaces for portlets and tags for JSPs called
by portlets, cleanly separating portlets from the surrounding
infrastructure so that portlets can run on different portal servers like
servlets can run on different application servers.

The Portlet API specification shall evolve from the portlet concept as
developed in the Apache JetSpeed Open Source project. In many aspects,
the Portlet API is an extension of the Servlet API, defining additional
interfaces for portlet-specific functionality. In some other aspects, it
restricts use of functions provided by the Servlet API to the subset
that makes sense for portlets just producing aggregatable markup
fragments and not having ownership of the entire page that displays
them. For example, unlike servlets, portlets may not send errors or
redirects as a response, this may only be done by the application that
invokes and aggregates the portlets into a larger page.
Portlets can be grouped in Portlet Applications. Portlets in one portlet
application can exchange messages via the Portlet API. Portlet
Applications are packaged, distributed and deployed using WAR files that
include portlet-related meta-information, utilizing existing Servlet
infrastructure.

The Portlet API shall be compatible with the Remote Portlet Web Services
concept in the sense that portlets written to the Portlet API can act as
local proxies in a portal server for remote portlet web services located
on other servers and portlets written to the Portlet API can be wrapped
into remote portlet web services.=20