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Introducing the Portlet Specification, Part 1
Get your feet wet with the specification's underlying terms and concepts
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Figure 1. Portal architecture. Click on thumbnail to view full-size image.
Page
Figure 2 depicts the basic portal page components. The portal page itself represents a complete markup document and aggregates several portlet windows. In addition to the portlets, the page may also consist of navigation areas and banners. A portlet window consists of a title bar with the portlet's title, decorations, and the content produced by the portlet. The decorations can include buttons to change the portlet's window state and mode (we explain these concepts later).
Figure 2. Portal page. Click on thumbnail to view full-size image.
Portlet
As mentioned above, a portlet is a Java-based Web component that processes requests and generates dynamic content. The content generated by a portlet is called a fragment, a piece of markup (e.g., HTML, XHTML, or WML (Wireless Markup Language)) adhering to certain rules. A fragment can be aggregated with other fragments to form a complete document, as shown in Figure 3. A portlet's content normally aggregates with the content of other portlets to form the portal page. A portlet container manages a portlet's life cycle.
Figure 3. Different portlet markups: on the left side, HTML markup in a desktop browser; on the right side, WML markup on a mobile phone. Click on thumbnail to view full-size image.
Web clients interact with portlets via a request/response paradigm implemented by the portal. Usually, users interact with content produced by portlets by, for example, following links or submitting forms, resulting in portlet actions being received by the portal, which then forward to the portlets targeted by the user's interactions.
The content generated by a portlet may vary from one user to another depending on the portlet's user configuration.
Portlet container
A portlet container runs portlets and provides them with the required runtime environment. A portlet container contains portlets and manages their life cycles. It also provides persistent storage mechanisms for the portlet preferences. A portlet container receives requests from the portal to execute requests on the portlets hosted by it. A portlet container is not responsible for aggregating the content produced by the portlets; the portal itself handles aggregation.
A portal and a portlet container can be built together as a single component of an application suite or as two separate components of a portal application.
Concepts
This section explains the basic programming concepts in JSR 168, such as a portlet's life cycle, interface, and modes and window states, as well as session access, persistent storage access, and how to include servlets and JSP pages.
Portlet life cycle
The basic portlet life cycle of a JSR 168 portlet is:
- Init: initialize the portlet and put the portlet into service
- Handle requests: process different kinds of action- and render-requests
- Destroy: put portlet out of service
The portlet container manages the portlet life cycle and calls the corresponding methods on the portlet interface.
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Resources
- Pluto reference implementation
http://jakarta.apache.org/pluto - Read the whole series, "Introducing the Portlet Specification," Stefan Hepper and Stephan Hesmer (JavaWorld):
- Part 1Get your feet wet with the specification's underlying terms and concepts (August 2003)
- Part 2The Portlet API's reference implementation reveals its secrets (September 2003)
- JSR 168
http://www.jcp.org/en/jsr/detail?id=168 - Information about WSRP
http://www.oasis-open.org/committees/wsrp/ - Information about the user profile attributes in P3P
http://www.w3c.org/TR/P3P - For more on portals and portlets, read the following JavaWorld articles
- "Go With the Flow," Brian Pontarelli and Grant Zemont (February 2003)
- "Develop Java Portlets," Carl Vieregger (February 2003)
- "Build Portals with Jetspeed," Jeff Linwood (July 2001)
- Browse the JavaServer Pages section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-jsp-index.shtml - Browse the Java and Web Services section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-webserv-index.shtml - Browse the Java 2 Platform, Enterprise Edition (J2EE) section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-j2ee-index.shtml - Browse the Servlets section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-servlets-index.shtml - Browse the Java Community Process of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-jcp-index.shtml - Browse the APIs section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-apis-index.shtml - Visit JavaWorld's Enterprise Java discussion
http://www.javaworld.com/javaforums/postlist.php?Cat=&Board=Enterprisejava - Sign up for JavaWorld's free weekly Enterprise Java email newsletter
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Excellent for beginnersBy Anonymous on December 15, 2009, 10:55 pmIts awesome...
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Nice oneBy Anonymous on November 11, 2009, 1:59 amThank you so much .it's veryuseful
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Nice articleBy Anonymous on September 18, 2009, 8:57 amIt is good introduction to portlets. Appreciate the efforts !
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A good tutorial finally !By Anonymous on June 26, 2009, 1:05 amA good tutorial finally !
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Great articleBy Anonymous on March 25, 2009, 9:32 pmThanks for this excellent arcticle.
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