Chapter 15. The Open APIs

Part of the process of designing software is deciding what functionality needs to be abstracted and exposed for extensibility and what should be encapsulated and invisible to someone extending the system. One good example is Presenter s. Presenters are NetBeans’ abstraction for components such as menu items and toolbar buttons—usually the default implementation is sufficient, and you simply specify an icon and display name and the runtime takes care of actually creating a user-interface component for them, but you can override this behavior if necessary.

The simplest way to let someone extend menus and toolbars is to give them access to a JMenu and let them add components to it. However, this is unmaintainable—if five third-party modules all add items to the File menu, the resulting interface is not likely to be very usable. In such a situation different modules might do things to the menu that interfere with each other working correctly, because there is no contract for how they should behave.

The solution is, appropriately, an abstraction that wraps concepts such as presentation of functionality, and even the Action abstraction for user-invokable behaviors. The goal is to give someone the ability to add functionality, not menu items per se. So we have the Actions, Menus, and Toolbars hierarchies in Tools Options IDE Configuration Look and Feel. As a result, it becomes possible to consistently integrate new functionality—the core takes care of presenting ...

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