What Is a Java Bean in Java

Generation Denso QR Bar Code in Java What Is a Java Bean

A Java Bean is a software component that has been designed to be reusable in a variety of different environments There is no restriction on the capability of a Bean It may perform a simple function, such as checking the spelling of a document, or a complex function, such as forecasting the performance of a stock portfolio A Bean may be visible to an end user One example of this is a button on a graphical user interface A Bean may also be invisible to a user Software to decode a stream of multimedia information in real time is an example of this type of building block Finally, a Bean may be designed to work autonomously on a user's workstation or to work in cooperation with a set of other distributed components Software to generate a pie chart from a set of data points is an example of a Bean that can execute locally However, a Bean that provides real-time price information from a stock or commodities exchange would need to work in cooperation with other distributed software to obtain its data We will see shortly what specific changes a software developer must make to a class so that it is usable as a Java Bean However, one of the goals of the Java designers was to make it easy to use this technology Therefore, the code changes are minimal

A software component architecture provides standard mechanisms to deal with software building blocks The following list enumerates some of the specific benefits that Java technology provides for a component developer:

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A Bean obtains all the benefits of Java's "write-once, run-anywhere" paradigm The properties, events, and methods of a Bean that are exposed to an application builder tool can be controlled A Bean may be designed to operate correctly in different locales, which makes it useful in global markets Auxiliary software can be provided to help a person configure a Bean This software is only needed when the design-time parameters for that component are being set It does not need to be included in the run-time environment The configuration settings of a Bean can be saved in persistent storage and restored at a later time A Bean may register to receive events from other objects and can generate events that are sent to other objects

When working with Java Beans, most developers use an application builder tool, a utility that enables you to configure a set of Beans, connect them together, and produce a working application Its major capabilities are the following: A palette is provided that lists all of the available Beans As additional Beans are developed or purchased, they can be added to the palette A worksheet is displayed that allows the designer to lay out Beans in a graphical user interface A designer may drag and drop a Bean from the palette to this worksheet Special editors and customizers allow a Bean to be configured This is the mechanism by which the behavior of a Bean may be adapted for a particular environment Commands allow a designer to inquire about the state and behavior of a Bean This information automatically becomes available when a Bean is added to the palette Capabilities exist to interconnect Beans This means that events generated by one component are mapped to method invocations on other components When a collection of Beans has been configured and connected, it is possible to save all of this information in a persistent storage area At a later time, this information can then be used to restore the state of the application

The Bean Developer Kit (BDK)

The Bean Developer Kit (BDK), available from the JavaSoft site, is a simple example of a tool that enables you to create, configure, and connect a set of Beans There is also a set of sample Beans with their source code This section provides step-by-step instructions for installing and using this tool Note In this chapter, instructions are provided for a Windows 95/98/NT environment The procedures for a UNIX platform are similar, but some of the commands are different