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An inside view of Observer
The Observer pattern facilitates communication between decoupled objects
Page 6 of 6
- Maintain a collection of listeners
- Implement
addPropertyChangeListener() - Notify listeners when a bound property changes
Once you implement the above steps, you can add property change listeners to your event source and react to events.
Listen and observe
The Observer design pattern is one of the most fundamental design patterns because it allows loosely coupled objects to communicate. That ability lets you create pluggable components, which lie at the heart of object-oriented extensibility and reuse.
About the author
David Geary is the author of Core JSTL Mastering the JSP Standard Tag Library (Prentice Hall, 2002; ISBN: 0131001531), Advanced JavaServer Pages (Prentice Hall, 2001; ISBN: 0130307041), and the Graphic Java series (Prentice Hall). David has been developing object-oriented software with numerous object-oriented languages for 18 years. Since the GOF Design Patterns book was published in 1994, David has been an active proponent of design patterns, and has used and implemented design patterns in Smalltalk, C++, and Java. In 1997, David began working full-time as an author and occasional speaker and consultant. David is a member of the expert groups defining the JSP Standard Tag Library and JavaServer Faces, and is a contributor to the Apache Struts JSP framework.Read more about Core Java in JavaWorld's Core Java section.
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Resources
- Download this article's complete source code as a jar file
http://www.javaworld.com/javaworld/jw-03-2003/designpatterns/jw-0328-designpatterns.jar - The famous Gang of Four bookDesign Patterns, Eric Gamma, Richard Helm, Ralph Johnson, John Vlissides (Addison-Wesley Publishing Co., 1995; ISBN0201633612)
http://www.amazon.com/exec/obidos/ASIN/0201633612/javaworld - Designing Object-Oriented Software, Rebecca Wirfs-Brock, Brain Wilkerson, and Lauren Wiener (Prentice-Hall, 1990; ISBN0136298257)
http://www.amazon.com/exec/obidos/ASIN/0136298257/javaworld - Object-Oriented Analysis and Design With Applications, Grady Booch (Addison-Wesley Publishing Co., 1994; ISBN0805353402)
http://www.amazon.com/exec/obidos/ASIN/0805353402/javaworld - Object-Oriented Software Construction, Second Edition, Bertrand Meyer (Prentice-Hall, 2000; ISBN0136291554)
http://www.amazon.com/exec/obidos/ASIN/0136291554/javaworld - Read David Geary's previous Java Design Patterns columns
http://www.javaworld.com/columns/jw-java-design-patterns-index.shtml - For more design pattern articles, visit the Design Patterns section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-patterns-index.shtml - Visit JavaWorld's Programming Theory & Practice discussion
http://forums.devworld.com/webx?50@@.ee6b806 - Sign up for JavaWorld's free weekly email newsletters
http://www.javaworld.com/subscribe - You'll find a wealth of IT-related articles from our sister publications at IDG.net
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