Introduction to JavaBean

A JavaBean is a reusable piece of software developed in java that supports three fundamentals of every component, which is events, properties and methods.

Features of JavaBean

Events or the power to advise its environment of special events and changes in state.
Properties or private fields through which data can be displayed.
Introspection or the power of external objects to examine the working of a bean.
Customization or the power to customize the appearance or behavior of a bean.
Persistence or mechanisms that enables storage of a bean for later use.

Use of JavaBean
Redistribution or reuse of code and code  compartmentalization are the two basic reasons why the java beans technology  came into existence. With the help of the java beans technology, a person can  create an entire application by simply using a graphical tool to connect some  bean components together.
Bean Development Kit
The Java Bean Development Kit (BDK), according to  Sun Microsystems, is intended to support the development of JavaBeans components  and to act as a standard reference base for both component developers and tool  vendors. The BDK includes a BeanBox, which is the JavaBeans reference container  and acts as an example of how to build your own bean container. The Beanbox  however is not an application development tool. It allows you to test the  functionality of your Bean components including properties and events.
BeanBox
BeanBox is a basic tool that Sun provides for  testing Java Beans. To run the BeanBox, your computer needs to have access to a  BDK installation. To run the BeanBox, go to the beans/beanbox subdirectory and  then type run. This will bring up three windows:

    
    The ToolBox window gives you a palette of sample  Java Beans to choose from.
    
    
    The BeanBox window is a container within which  you can visually wire beans together.
    
    
    The Properties window allows you to edit the  properties of the currently selected Java Bean.
    

Creating a Java Bean
This example illustrates how to create a simple  Java Bean. Java Bean classes must be made Serializable so that they support  persistent storage. To make use of the default serialization capabilities in  Java, the class needs to implement the Serializable interface or inherit a class  that implements the Serializable interface. It just serves as a flag to say that  the designer has tested the class to make sure it works with default  serialization. Here is the code:
SimpleBean.java

    
        
            
            import java.awt.*;
            import java.io.Serializable;
            public class SimpleBean extends Canvas implements Serializable  {
            //Constructor sets inherited properties
                public SimpleBean() {
                    setSize(60,40);
                    setBackground(Color.red);
                }
            }
            
        
    

Since this class extends a GUI component,  java.awt.Canvas, it will be a visible Java Bean. Java Beans may also be  invisible. Now the Java Bean must be compiled and packaged into a JAR file.  First run the compiler: javac SimpleBean.java Then create a manifest file  manifest.tmp Name: SimpleBean.class Java-Bean: True Finally create the JAR file:  jar cfmv SimpleBean.jar manifest.tmp SimpleBean.class. The JAR file can now be  placed in the beans/jars so that the BeanBox will find it on startup, or it can  be loaded subsequently by choosing File | LoadJar.