Question

I am building an Eclipse plug-in that provides a set of core features in the regular plug-in project. The optional features I am providing via fragment projects. But I need the fragments to register themselves with the main plug-in on start-up.

I cannot have a Bundle-Activator in the fragment project. So I am wondering is there some alternate mechanism to declare an entry point or some call-back that I can hook?

And if there is no alternative other than converting the fragment project to a regular plug-in project is there a downside that I need to be aware of?

This is the solution I used based on the accepted answer:

final IExtensionRegistry registry = Platform.getExtensionRegistry(); final IExtensionPoint extensionPoint = registry.getExtensionPoint('myextensionid'); final IExtension[] extensions = extensionPoint.getExtensions(); for (int j = 0; j < extensions.length; ++j) {     final IConfigurationElement[] points = extensions[j].getConfigurationElements();     for (int i = 0; i < points.length; ++i)     {         if ('myelementname'.equals(points[i].getName()))         {             try             {                 final Object objImpl= points[i].createExecutableExtension('class');                 objImplList.add(provider);             }             catch (CoreException e)             {             }         }     } } 

Answer 1

You could define an extension point and lookup/call your fragment classes via extensions.

    IExtensionRegistry registry = Platform.getExtensionRegistry();     IExtensionPoint extensionPoint = registry             .getExtensionPoint('myplugin.myextension');     IConfigurationElement points[] = extensionPoint             .getConfigurationElements();     for (IConfigurationElement point : points) {         if ('myextensionFactory'.equals(point.getName())) {             Object impl = point.createExecutableExtension('class');             if (impl instanceof IMyExtension) {                 ((IMyExtension) impl).foo();             }         }     } } 

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EDIT:

To use this approach I have to convert my fragments projects to plug-in projects. – bmatthews68

You shouldn’t have to. For example, in my test code, I have the following files in the host plugin:

META-INF/MANIFEST.MF:

Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: Myplugin Plug-in Bundle-SymbolicName: myplugin;singleton:=true Bundle-Version: 1.0.0 Bundle-Activator: myplugin.Activator Require-Bundle: org.eclipse.core.runtime Eclipse-LazyStart: true Export-Package: myplugin 

plugin.xml:

<?xml version='1.0' encoding='UTF-8'?> <?eclipse version='3.2'?> <plugin>     <extension-point id='myextension' name='myextension'         schema='schema/myextension.exsd' /> </plugin> 

The fragment contains these files:

META-INF/MANIFEST.MF:

Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: Myfragment Fragment Bundle-SymbolicName: myfragment;singleton:=true Bundle-Version: 1.0.0 Fragment-Host: myplugin;bundle-version='1.0.0' 

fragment.xml:

<?xml version='1.0' encoding='UTF-8'?> <?eclipse version='3.2'?> <fragment>    <extension          point='myplugin.myextension'>       <myextensionFactory             class='myfragment.MyExtension1'>       </myextensionFactory>    </extension> </fragment> 

These projects were generated using Eclipse 3.3.1.1.