2.2 Inside Plug-ins
Now that you’ve seen the 10,000- and 1,000-foot views of Eclipse, let’s drop down to 100 feet and look at plug-ins, the basic building blocks of Eclipse. A plug-in is a collection of files and a manifest that describe the plug-in and its relationships to other plug-ins.
Figure 2–3 Plug-in disk layout
Figure 2–3 shows the layout of the org.eclipse.ui plug-in. The first thing to notice is that the plug-in is a Java Archive (JAR), org.eclipse.ui_3.1.0.jar. As a JAR, it has a MANIFEST.MF. The manifest includes a description of the plug-in and its relationship to the rest of the world.
Plug-ins can contain code and/or read-only content such as images, Web pages, translated message files, documentation, and so on. For instance, the UI plug-in in Figure 2–3 has code in the org/eclipse/ui/... directory structure and other content in icons/ and about.html.
Notice that the plug-in also has a plugin.xml file. Historically, that was the home of the execution-related information now stored in the MANIFEST.MF. The plugin.xml continues to be the home of any extension and extension point declarations contributed by the plug-in.