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JavaServer Faces by Hans Bergsten

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Developing a New Component from Scratch

In Chapter 13 and the previous section of this chapter, you’ve seen how custom renderers can be used to customize the presentation of a standard component, and if that’s not enough, how to extend an existing component to get a component with a slightly different behavior. These options cover most possibilities, and you very rarely need to develop a brand new component class. In fact, I had a hard time coming up with an example for this section. I wanted to develop a fairly simple component to illustrate the main points, but it turns out that all the simple components are provided already as standard JSF components, and almost any customization is better done with a custom renderer.

The only component I could think of that must be implemented from scratch (except for the basic behavior inherited from UIComponentBase) is a tree control, where nodes in a tree structure can be expanded or collapsed. It’s a far more complex example than what I first had in mind, but I believe it’s still a good one. Be aware, though, that this is not for the faint of heart so hold on tight as we dig deep into the intricacies of the JSF component API and its interaction with other JSF classes and the request processing lifecycle.

Figure 14-2 shows the tree control in action, exploring the component state information captured by the CaptureStatePhaseListener discussed in Chapter 12.

Figure 14-2. Tree control with captured component state nodes

In Figure 14-2, I use folder ...

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