EDIT

@XmlRootElement(name = "Group")

@Entity

public class GrantedAuthorityImpl extends CdmBase implements GrantedAuthority {

    private static final long serialVersionUID = 2651969425860655040L;

    private static final Logger logger = Logger

            .getLogger(GrantedAuthority.class);

        return new GrantedAuthorityImpl();

    }

    public String getAuthority() {

        return authority;

    }

        this.authority = authority;

    }

    public int compareTo(Object o) {

        if (o instanceof GrantedAuthority) {

            return this.authority.compareTo(((GrantedAuthority) o)

            return null;

        }

    }

}