protected void updateGroupMembership(
      SlingHttpServletRequest request,
      Session session,
      Authorizable authorizable,
      String paramName,
      List<Modification> changes,
      Map<String, Object> toSave)
      throws AccessDeniedException, StorageClientException {
    if (authorizable instanceof Group) {
      Group group = ((Group) authorizable);
      String groupPath =
          LiteAuthorizableResourceProvider.SYSTEM_USER_MANAGER_GROUP_PREFIX + group.getId();

      boolean changed = false;

      AuthorizableManager authorizableManager = session.getAuthorizableManager();

      // first remove any members posted as ":member@Delete"
      String[] membersToDelete =
          request.getParameterValues(paramName + SlingPostConstants.SUFFIX_DELETE);
      if (membersToDelete != null) {
        toSave.put(group.getId(), group);
        LOGGER.info("Members to delete {} ", membersToDelete);
        for (String member : membersToDelete) {
          String memberId = getAuthIdFromParameter(member);
          group.removeMember(memberId);
          changed = true;
        }
      }

      Joinable groupJoin = getJoinable(group);

      // second add any members posted as ":member"
      String[] membersToAdd = request.getParameterValues(paramName);
      if (membersToAdd != null) {
        LOGGER.info("Members to add {} ", membersToAdd);
        Group peerGroup = getPeerGroupOf(group, authorizableManager, toSave);
        List<Authorizable> membersToRemoveFromPeer = new ArrayList<Authorizable>();
        for (String member : membersToAdd) {
          String memberId = getAuthIdFromParameter(member);
          Authorizable memberAuthorizable = (Authorizable) toSave.get(memberId);
          if (memberAuthorizable == null) {
            memberAuthorizable = authorizableManager.findAuthorizable(memberId);
          }
          if (memberAuthorizable != null) {
            if (!User.ADMIN_USER.equals(session.getUserId())
                && !UserConstants.ANON_USERID.equals(session.getUserId())
                && Joinable.yes.equals(groupJoin)
                && memberAuthorizable.getId().equals(session.getUserId())) {
              LOGGER.debug("Is Joinable {} {} ", groupJoin, session.getUserId());
              // we can grab admin session since group allows all users to join
              Session adminSession = getSession();
              try {
                AuthorizableManager adminAuthorizableManager =
                    adminSession.getAuthorizableManager();
                Group adminAuthGroup =
                    (Group) adminAuthorizableManager.findAuthorizable(group.getId());
                if (adminAuthGroup != null) {
                  adminAuthGroup.addMember(memberAuthorizable.getId());
                  adminAuthorizableManager.updateAuthorizable(adminAuthGroup);
                  changed = true;
                }
              } finally {
                ungetSession(adminSession);
              }
            } else {
              LOGGER.info(
                  "Group {} is not Joinable: User {} adding {}  ",
                  new Object[] {
                    group.getId(), session.getUserId(), memberAuthorizable.getId(),
                  });
              // group is restricted, so use the current user's authorization
              // to add the member to the group:

              group.addMember(memberAuthorizable.getId());
              if (LOGGER.isInfoEnabled()) {
                LOGGER.info(
                    "{} Membership now {} {} {}",
                    new Object[] {
                      group.getId(),
                      Arrays.toString(group.getMembers()),
                      Arrays.toString(group.getMembersAdded()),
                      Arrays.toString(group.getMembersRemoved())
                    });
              }
              toSave.put(group.getId(), group);
              Group gt = (Group) toSave.get(group.getId());
              if (LOGGER.isInfoEnabled()) {
                LOGGER.info(
                    "{} Membership now {} {} {}",
                    new Object[] {
                      group.getId(),
                      Arrays.toString(gt.getMembers()),
                      Arrays.toString(gt.getMembersAdded()),
                      Arrays.toString(gt.getMembersRemoved())
                    });
              }
              changed = true;
            }
            if (peerGroup != null && peerGroup.getId() != group.getId()) {
              Set<String> members = ImmutableSet.of(peerGroup.getMembers());
              if (members.contains(memberAuthorizable.getId())) {
                membersToRemoveFromPeer.add(memberAuthorizable);
              }
            }
          } else {
            LOGGER.warn("member not found {} ", memberId);
          }
        }
        if ((peerGroup != null) && (membersToRemoveFromPeer.size() > 0)) {
          for (Authorizable member : membersToRemoveFromPeer) {
            if (LOGGER.isInfoEnabled()) {
              LOGGER.info("Removing Member {} from {} ", member.getId(), peerGroup.getId());
            }
            peerGroup.removeMember(member.getId());
          }
          toSave.put(peerGroup.getId(), peerGroup);
          if (LOGGER.isInfoEnabled()) {
            LOGGER.info(
                "{} Just Updated Peer Group Membership now {} {} {}",
                new Object[] {
                  peerGroup.getId(),
                  Arrays.toString(peerGroup.getMembers()),
                  Arrays.toString(peerGroup.getMembersAdded()),
                  Arrays.toString(peerGroup.getMembersRemoved())
                });
          }
        }
      }

      if (changed) {
        // add an entry to the changes list to record the membership
        // change
        changes.add(Modification.onModified(groupPath + "/members"));
      }
    }
  }
  @SuppressWarnings("unchecked")
  public void onMessage(Message message) {
    log.debug("Receiving a message on {} : {}", SyncJMSMessageProducer.QUEUE_NAME, message);
    try {

      String topic = message.getJMSType();
      String groupId = (String) message.getStringProperty("path");

      String operation = "UNKNOWN";

      // A group was DELETED
      if ("org/sakaiproject/nakamura/lite/authorizables/DELETE".equals(topic)
          && config.getDeletesEnabled()) {
        Map<String, Object> attributes =
            (Map<String, Object>) message.getObjectProperty(StoreListener.BEFORE_EVENT_PROPERTY);
        grouperManager.deleteGroup(groupId, attributes);
        operation = "DELETED";
      }

      // A new group was ADDED or an existing group was UPDATED
      if ("org/sakaiproject/nakamura/lite/authorizables/ADDED".equals(topic)
          || "org/sakaiproject/nakamura/lite/authorizables/UPDATED".equals(topic)) {
        // These events should be under org/sakaiproject/nakamura/lite/authorizables/UPDATED
        // http://jira.sakaiproject.org/browse/KERN-1795
        String membersAdded =
            (String) message.getStringProperty(GrouperEventUtils.MEMBERS_ADDED_PROP);
        if (membersAdded != null) {
          // membership adds can be attached to the same event for the group add.
          grouperManager.createGroup(groupId, config.getGroupTypes());
          grouperManager.addMemberships(
              groupId, Arrays.asList(StringUtils.split(membersAdded, ",")));
          operation = "ADD_MEMBERS";
        }

        String membersRemoved =
            (String) message.getStringProperty(GrouperEventUtils.MEMBERS_REMOVED_PROP);
        if (membersRemoved != null) {
          grouperManager.removeMemberships(
              groupId, Arrays.asList(StringUtils.split(membersRemoved, ",")));
          operation = "REMOVE_MEMBERS";
        }

        if (membersAdded == null && membersRemoved == null) {
          org.sakaiproject.nakamura.api.lite.Session repositorySession =
              repository.loginAdministrative();
          AuthorizableManager am = repositorySession.getAuthorizableManager();
          Group group = (Group) am.findAuthorizable(groupId);
          repositorySession.logout();

          if (groupId.startsWith(ContactsGrouperNameProviderImpl.CONTACTS_GROUPID_PREFIX)) {
            // TODO Why are we not getting added and removed properties on the Message
            grouperManager.createGroup(groupId, null);
            grouperManager.addMemberships(groupId, Arrays.asList(group.getMembers()));
            operation = "UPDATE CONTACTS";
          } else {
            grouperManager.createGroup(groupId, config.getGroupTypes());
            grouperManager.addMemberships(groupId, Arrays.asList(group.getMembers()));
            operation = "CREATE";
          }
        }
      }

      // The message was processed successfully. No exceptions were thrown.
      // We acknowledge the message and its removed from the queue
      message.acknowledge();

      // We got a message that we didn't know what to do with.
      if (operation.equals("UNKNOWN")) {
        log.error(
            "I don't know what to do with this topic: {}. Turn on debug logs to see the message.",
            topic);
        log.debug(message.toString());
      } else {
        log.info("Successfully processed and acknowledged. {}, {}", operation, groupId);
        log.debug(message.toString());
      }

    } catch (JMSException jmse) {
      log.error("JMSException while processing message.", jmse);
    } catch (Exception e) {
      log.error("Exception while processing message.", e);
    }
  }