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Trail: JavaBeans(TM)
Lesson: Using the BeanContext API

Overview of the BeanContext API

Purpose

As stated in the specification, the purpose of the Extensible Runtime Containment and Services Protocol is "to introduce the concept of a relationship between a Component and its environment, or Container, wherein a newly instantiated Component is provided with a reference to its Container or Embedding Context. The Container, or Embedding Context not only establishes the hierarchy or logical structure, but it also acts as a service provider that Components may interrogate in order to determine, and subsequently employ, the services provided by their Context."

This protocol supports extensible mechanisms that:

In English, this means that there now exists a standard mechanism through which Java developers can logically group a set of related JavaBeans into a "context" that the beans can become aware of and/or interact with. This context, or "containing environment", is known as the BeanContext.

There are two distinct types of BeanContext included in this protocol: one which supports membership only (interface java.beans.beancontext.BeanContext (in the API reference documentation)) and one which supports membership and offers services (interface java.beans.beancontext.BeanContextServices (in the API reference documentation)) to its JavaBeans nested within.

To orient yourself with the classes and interfaces of java.beans.beancontext, take a minute to look over the following hierarchy diagram. You will notice that the majority of the package is defined as interfaces, which allow for multiple inheritance.

Inheritance Diagram of the BeanContext API

The classes and interfaces relevant to the BeanContext API are listed in the following diagrams. As you study the diagrams, take note of the BeanContext and BeanContextServices interfaces, and that each has its own concrete implementation that you can subclass or instantiate directly (classes java.beans.beancontext.BeanContextSupport (in the API reference documentation) and java.beans.beancontext.BeanContextServicesSupport (in the API reference documentation) respectively). Also take note of the location of the java.beans.beancontext.BeanContextChild (in the API reference documentation) interface. This is the interface that allows nested JavaBeans to become aware of their enclosing BeanContext.


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