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Development of reusable component architectures that will allow
large software systems to be designed by combining components from possibly different
sources is the intended goal of JavaBeans. JavaBeans provides mechanisms to define
components in Java and specify interactions amongst them. Java Beans components provide
support wherein component assemblers discover properties about components. One of the
other interesting aspect about JavaBeans is that it also accommodates other component
architectures such as OpenDoc, ActiveX and LiveConnect. So by writing to JavaBeans the
developer is assured that the components can be used in these and other component
architectures.
The bean that we present here is the Image-Editing bean detailed in
Section 2.4.5.5 in the Java
Chapter.
Source : (Image Editing Bean)
(a) sunw/demo/ImageEditor/ImageEditor.java
(b) sunw/demo/ImageEditor/FilterNameEditor.java
(c) sunw/demo/ImageEditor/ImageEditorBeanInfo.java
NOTE: A class that provides explicit information about a
bean must implement the BeanInfo interface or extend a class that implements it.
This interface identifies all of the methods that a framework needs in order to introspect
a bean.
You specify the name of the bean info class by adding BeanInfo to the
name of the bean. For example, the bean info class associated to the class ImageEditor
must be named ImageEditorBeanInfo. The bean info class must be part of the same
package as the bean itself.
(d) Resource files:
sunw/demo/ImageEditor/faces.gif,
sunw/demo/ImageEditor/ImageScaleIconColor16.gif,
sunw/demo/ImageEditor/ImageScaleIconColor32.gif,
sunw/demo/ImageEditor/ImageScaleIconMono16.gif,
sunw/demo/ImageEditor/ImageScaleIconMono32.gif
Makefile:
Compiling a bean is very similar to compiling a Java class. A bean,
however, usually consists of more than one class: it can have an icon, a customizer, a
BeanInfo class, and so on. Therefore, all of the bean class files and all other resource
files must be packaged and delivered as a unit. JDK1.1 provides a utility, called Java
archive (JAR), that supports the ZIP format and can bundle a number of files into one
flat JAR file. Another complication when compiling a bean is the configuration management.
Because a bean comprises more than one file, we need to ensure that proper versions of
files are packaged together and that the JAR file is recreated whenever any of the bean's
files changes. The best way to manage this complexity is through the use of makefiles.
ImageEditor.mk
JAR Files: Please refer to the Java-Basics section for more information on using JAR
files.
ImageEditor.jar
Another Example: (TextEditor Bean)