Human Worklist group authentication

As I have written an article that is using database authentication within the SOA suite for human tasks, this soultion is not complete. Apart of the pointing reference to the example "workflow-120-SQLIdentityProvider", this example is not available for download (yet).
The solution is wokring, but it does not work for groups. If you assign an task to:

• a user, you can use the task in the worklist application.
• a user AND group, you can use/claim the task in the worklist application.
• a group, an error occurs in the assignement. 

 The issue is not the SQLAuthenticator or the configuration of weblogic. But it is the custom java code that is used in the custom identity provider.

Follow the instruction in my previous article, but now use the new Java code, summary:

1. Apply the SQL Authenticator in your SOA WLS environment.
2. Test if users and groups can be viewed and edited.
3. Shutdown the admin server and managed servers.
4. Copy the dbprovider.jar to the SOA_DOMAIN/lib directory
5. make changes in the SOA FMW  JPS config file:
6. Start admin and managed servers
7. Test the worklist application with database users.
8. Configure SQL Authenticator in WebLogic Server
9. Add a new Identity Store.
10. Add a new Service Instance.
11. Change JpsContext to the new Identity store.