THIS IS EXPERIMENTAL! IT IS NOT OFFICIALLY SUPPORTED NEITHER BY RAP NOR BY EMF
EMFs runtime part should work out of the box with RAP as there are no dependencies to UI-related stuff. The only thing to be aware of is the dependency to the Eclipse Resources (aka Workspace).
EMF relies in the UI parts on the Resource infrastructure to support seamless integration with the Eclipse workspace. This is a big problem as the resource framework is multi-user enabled and thus can lead to problem in the RAP environment. Even if there may be workarounds available (eg. session-scoped EFS implementation), there is still only one workspace available. This can lead to big problems like a user who locks the workspace automatically locks all other users in the webapp.
UI and Edit Framework
Generated edtitors of EMF (and in particular their dependencies) have to be modified to run on RAP. The two interesting bundles from EMF are:
With the support for cell editors in the properties view and D&D, many problems from the past have vanished. But there are still many references to IDE- and Resource-specific features that will not be available in RAP. This should be a topic to discuss further how to resolve this. That resources will be session-scoped is out of the context of the 3.x stream of the platform. This *may* come with e4 but at the moment, there are committers working on this. Another option would be to split the EMF-bundles in EMF-Core and Resource-Integration bundles. As the dependencies to resource is rather broad, this could lead to many API breaks which is not very good either. Single-sourcing the EMF-Bundles as they are with the dependency to the Resources framework would lead to a situtation where users could use them but have to be aware of the fact they should never use any API that may, even accidentally, call into the resources infrastructure.
As the whole EMF UI story has a strong dependency to the IDE bundle of Eclipse (org.eclipse.ui.ide), we need to support this somehow. This is rather problematic as IDE itself relies heavily on the Resource infrastructure. As simple mock is attached to the bug report stated in the References section. This is not intended to be used outside of the research/evaluation process.
The demo consists of a patch for the EMF-UI plugins, a mock of the IDE bundle and the EMF library example. As host we use a pretty simple RAP application (org.eclipse.rap.demo). The whole source can be found in the zip attached to the corresponding bug report.