code: public boolean unlock(final CmsUUID structureId) {
  
          // lock the sitemap
          CmsRpcAction<String> unlockAction = new CmsRpcAction<String>() {
  
              /**
              * @see org.opencms.gwt.client.rpc.CmsRpcAction#execute()
              */
              @Override
              public void execute() {
  
                  start(200, false);
                  getService().unlock(structureId, this);
              }
  
              /**
              * @see org.opencms.gwt.client.rpc.CmsRpcAction#onResponse(java.lang.Object)
              */
              @Override
              public void onResponse(String result) {
  
                  stop(false);
                  if (result == null) {
                      // ok
                      return;
                  }
                  // unable to lock
                  String text = Messages.get().key(Messages.GUI_UNLOCK_NOTIFICATION_2, structureId.toString(), result);
                  CmsNotification.get().send(CmsNotification.Type.WARNING, text);
              }
          };
          return unlockAction.executeSync() == null;
      }
docs: Unlocks the given resource, synchronously.<p>
  
  @param structureId the resource structure id
  
  @return <code>true</code> if succeeded, if not a a warning is already shown to the user