Download Java Beans

By Dr. Jiang B. Liu
12. The Java Beans
Java Beans
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JavaBeans is a portable, platform-independent software
component model written in Java. It enables developers to write
reusable components once and run them anywhere - benefiting
from the platform-independent power of Java.
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Beans may be manipulated in a visual builder tool and composed
together into applications. A Bean is any Java class which adheres
to certain property and event interface conventions.
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The Beans Development Kit (BDK) provides support for the
JavaBeans APIs and a test container (the “BeanBox” to test Bean
behavior),
Network Computing: Java Beans
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JavaBeans Network Component Computing Model
JavaBeans
OSes Supported
Virtually all
HTTP Servers Supported
JavaSoft’s Java Web Server;
others to come
Programming Languages
Java
Component Model
JavaBeans
Network Component Model
CORBA IIOP or Java RMI
Java Beans in the Java Enterprise Architecture
Java Beans: Caracteristic features
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Introspection: Enables a builder tool to analyze how a bean works.
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Customization: Enables the developer of a Bean component to customize
the appearance and behavior of a Bean.
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Events: Enables beans to fire events and informing builder tools about
the events they can fire and the events they can handle.
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Properties:Supports the customization mentioned above.
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Persistence: Enables developers to customize Beans, and then retrieve
those Beans later, with customized features intact.
Java Beans: Create a Java Bean
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1. Create a Bean (jar) file
jar cfm FancyButton.jar \
FancyButton.mf FancyButton.class FancyButton.gif
FancyButton.au
(FancyButton.mf:
Manifest-Version: 1.0
Name: FancyButton.class
Java-Bean: True)
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2. Copy the Bean file to C:\BDK1.0\jars
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3. Test the Bean in the BeanBox.
Java Beans: JAR Files
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A JAR file is a convenient way of packaging together a set of class files
and any associated GIF images, data files, or other resource files.
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A JAR file consists of a normal ZIP format file, plus an optional
manifest file describing the JAR contents.
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You can use the JDK 1.1 jar command to create and read JAR files.
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Manifest file: Each JAR file may contest a manifest file describing the
contents of the JAR file.
Java Beans: JAR Files
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The jar command
The jar command is provided as part of JDK 1.1. It allows you to
either create a JAR file or to extract the content of a jar file.
The jar command syntax is:
jar [ctxvfm] [jar-file] [manifest-file] files …
Option flags are:
c create new archive
t list table of contents for archive
x extract named (or all) files from archive
v generate verbose output on standard error
f specify JAR file name
m include manifest information from specified manifest file
If any file is a directory then it is processed recursively.
Java Beans: BeanBox
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The BeanBox is a very simple test container. It allows you to try
out beans.
The BeanBox allows you to:
drop beans onto a composition window
resize and move beans around
edit the exported properties of a bean
run a customizer to configure a bean
connect a bean event source to an event handler method
connect together bound properties on different beans
save and restore sets of beans
get an introspection report on a bean
add new beans from JAR files
Java Beans: Create an Application using Beans
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1. Run BeanBox
java sun.beanbox.BeanBoxFrameset
(CLASSPATH=%CLASSPATH%;C:\JavaBdk1.0\beanbox\CLASSES)
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2. Create an instance of Juggler bean and two instance of OurButton
beans. (using Toolbox) Rename the button label (using PropertySheet)
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3. Select the button bean and connected to the Juggler bean.
(Edit->event->action->actionPerform->Click on the Juggler>start/stop method in EventTargetDialog)
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4. Save the application (File->save)
Java BeanBox