Learning Java

Chapter 19. Java Beans

JavaBeans^[49] is a component architecture for Java. It is a set of rules for writing highly reusable software elements that can be linked together in a “plug and play” fashion to build applications. Writing objects to the JavaBeans specification means you will have to write less custom code to glue them together. It also allows you to leverage JavaBean-aware development tools. With some graphical development environments, it is even possible to build complete applications just by connecting prefabricated Java Beans.

JavaBeans is a rich topic, and we can’t give it more than a brief overview here. If this overview whets your appetite, look for Developing Java Beans by Robert Englander (O’Reilly & Associates).

What’s a Bean?

So, what exactly is or are Java Beans? JavaBeans defines a set of rules; Java Beans are ordinary Java objects that play by these rules. That is, Java Beans are Java objects that conform to the JavaBeans API and design patterns. By doing so they can be recognized and manipulated within visual application builder environments. Beans live and work in the Java runtime system, as do all Java objects. They communicate with their neighbors using events and other normal method invocations.

For examples of Beans, we have to look no further than the javax.swing packages. All of the familiar components, like JButton, JTextArea, JScrollpane, etc., are not only suggestive of things suitable to be Beans, but are, in fact, Beans! Much of what you learned in ...