You've missed some imports ?
Because if your class is on package es.git.openkm.core; ( file writen ) then you need some imports
import es.git.openkm.core.principal.PrincipalAdapter;
import es.git.openkm.core.principal.PrincipalAdapterException;
and you must implement the method getMails
public Collection<String> getMails(Collection<String> users)
throws PrincipalAdapterException {
// TODO Auto-generated method stub
return null;
}
Without it your code can compile correctly.
Have you take a look about actual
developer guide, if not look it please, because I think it's not possible jboss-ide ( eclipse ) don't detects problems.