So far, we've been looking at the different extensions that are provided by the contributions plug-in. Let's look at the general definition of the contributions plug-in.
The readme tool plug-in is defined in the MANIFEST.MF file.
Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: %contributions.Activator.name Bundle-SymbolicName: org.eclipse.ui.examples.contributions; singleton:=true Bundle-Version: 3.3.100.qualifier Bundle-Activator: org.eclipse.ui.examples.contributions.Activator Require-Bundle: org.eclipse.ui;bundle-version="[3.3.0,4.0.0)", org.eclipse.core.runtime, org.eclipse.core.expressions;bundle-version="[3.3.0,4.0.0)" Bundle-Vendor: %contributions.Activator.providerName Bundle-Localization: plugin Bundle-RequiredExecutionEnvironment: J2SE-1.4 Bundle-ActivationPolicy: lazy
The plug-in definition includes the Bundle-Name, Bundle-SymbolicName (plug-in id), Bundle-Version, and Bundle-Vendor of the plug-in. We saw most of these parameters before in our hello world plug-in. The contribution plug-in also defines a specialized plug-in class, org.eclipse.ui.examples.contributions.Activator.
The Require-Bundle element informs the platform of the contribution plug-in's dependencies. The workbench UI plug-ins are listed as required plug-ins, along with the various core and expression plug-ins.
The Activator class represents the contribution plug-in and manages the life cycle of the plug-in. As we saw in the Hello World example, you don't have to specify a plug-in class. The platform will provide one for you. In this case, our plug-in needs to initialize UI related data when it starts up. The platform class AbstractUIPlugin provides a structure for managing UI resources and is extended by Activator.
AbstractUIPlugin uses the generic startup and shutdown methods to manage images, dialog settings, and a preference store during the lifetime of the plug-in.