#vulnerable code 
                              @Override
  public void execute(final ClusterEvent event) throws Exception {
    _eventId = event.getEventId();
    HelixManager manager = event.getAttribute(AttributeName.helixmanager.name());
    Map<String, Resource> resourceMap = event.getAttribute(AttributeName.RESOURCES.name());
    ClusterDataCache cache = event.getAttribute(AttributeName.ClusterDataCache.name());

    if (manager == null || resourceMap == null || cache == null) {
      throw new StageException("Missing attributes in event:" + event
          + ". Requires ClusterManager|RESOURCES|DataCache");
    }

    HelixDataAccessor dataAccessor = manager.getHelixDataAccessor();
    PropertyKey.Builder keyBuilder = dataAccessor.keyBuilder();

    CurrentStateOutput currentStateOutput =
        event.getAttribute(AttributeName.CURRENT_STATE.name());

    List<ExternalView> newExtViews = new ArrayList<>();

    Map<String, ExternalView> curExtViews = cache.getExternalViews();

    for (String resourceName : resourceMap.keySet()) {
      ExternalView view = new ExternalView(resourceName);
      // view.setBucketSize(currentStateOutput.getBucketSize(resourceName));
      // if resource ideal state has bucket size, set it
      // otherwise resource has been dropped, use bucket size from current state instead
      Resource resource = resourceMap.get(resourceName);
      if (resource.getBucketSize() > 0) {
        view.setBucketSize(resource.getBucketSize());
      } else {
        view.setBucketSize(currentStateOutput.getBucketSize(resourceName));
      }

      int totalPendingMessageCount = 0;

      for (Partition partition : resource.getPartitions()) {
        Map<String, String> currentStateMap =
            currentStateOutput.getCurrentStateMap(resourceName, partition);
        if (currentStateMap != null && currentStateMap.size() > 0) {
          // Set<String> disabledInstances
          // = cache.getDisabledInstancesForResource(resource.toString());
          for (String instance : currentStateMap.keySet()) {
            // if (!disabledInstances.contains(instance))
            // {
            view.setState(partition.getPartitionName(), instance, currentStateMap.get(instance));
            // }
          }
        }
        totalPendingMessageCount +=
            currentStateOutput.getPendingMessageMap(resource.getResourceName(), partition).size();
      }

      // Update cluster status monitor mbean
      IdealState idealState = cache.getIdealState(resourceName);
      if (!cache.isTaskCache()) {
        ResourceConfig resourceConfig = cache.getResourceConfig(resourceName);
        ClusterStatusMonitor clusterStatusMonitor =
            event.getAttribute(AttributeName.clusterStatusMonitor.name());
        if (clusterStatusMonitor != null) {
          if (idealState != null && (resourceConfig == null || !resourceConfig
              .isMonitoringDisabled())) {
            if (!idealState.getStateModelDefRef()
                .equalsIgnoreCase(DefaultSchedulerMessageHandlerFactory.SCHEDULER_TASK_QUEUE)) {
              StateModelDefinition stateModelDef =
                  cache.getStateModelDef(idealState.getStateModelDefRef());
              clusterStatusMonitor
                  .setResourceStatus(view, cache.getIdealState(view.getResourceName()),
                      stateModelDef);
              clusterStatusMonitor
                  .updatePendingMessages(resource.getResourceName(), totalPendingMessageCount);
            }
          } else {
            // Drop the metrics if the resource is dropped, or the MonitorDisabled is changed to true.
            clusterStatusMonitor.unregisterResource(view.getResourceName());
          }
        }
      }
      ExternalView curExtView = curExtViews.get(resourceName);
      // copy simplefields from IS, in cases where IS is deleted copy it from existing ExternalView
      if (idealState != null) {
        view.getRecord().getSimpleFields().putAll(idealState.getRecord().getSimpleFields());
      } else if (curExtView != null) {
        view.getRecord().getSimpleFields().putAll(curExtView.getRecord().getSimpleFields());
      }

      // compare the new external view with current one, set only on different
      if (curExtView == null || !curExtView.getRecord().equals(view.getRecord())) {
        // Add external view to the list which will be written to ZK later.
        newExtViews.add(view);

        // For SCHEDULER_TASK_RESOURCE resource group (helix task queue), we need to find out which
        // task partitions are finished (COMPLETED or ERROR), update the status update of the original
        // scheduler message, and then remove the partitions from the ideal state
        if (idealState != null
            && idealState.getStateModelDefRef().equalsIgnoreCase(
            DefaultSchedulerMessageHandlerFactory.SCHEDULER_TASK_QUEUE)) {
          updateScheduledTaskStatus(view, manager, idealState);
        }
      }
    }

    List<String> externalviewsToRemove = new ArrayList<>();
    // TODO: consider not setting the externalview of SCHEDULER_TASK_QUEUE at all.
    // Are there any entity that will be interested in its change?

    // For the resource with DisableExternalView option turned on in IdealState
    // We will not actually create or write the externalView to ZooKeeper.
    List<PropertyKey> keys = new ArrayList<>();
    for(Iterator<ExternalView> it = newExtViews.iterator(); it.hasNext(); ) {
      ExternalView view = it.next();
      String resourceName = view.getResourceName();
      IdealState idealState = cache.getIdealState(resourceName);
      if (idealState != null && idealState.isExternalViewDisabled()) {
        it.remove();
        // remove the external view if the external view exists
        if (curExtViews.containsKey(resourceName)) {
          LogUtil
              .logInfo(LOG, _eventId, "Remove externalView for resource: " + resourceName);
          dataAccessor.removeProperty(keyBuilder.externalView(resourceName));
          externalviewsToRemove.add(resourceName);
        }
      } else {
        keys.add(keyBuilder.externalView(resourceName));
      }
    }

    // add/update external-views
    if (newExtViews.size() > 0) {
      dataAccessor.setChildren(keys, newExtViews);
      cache.updateExternalViews(newExtViews);
    }

    // remove dead external-views
    for (String resourceName : curExtViews.keySet()) {
      if (!resourceMap.keySet().contains(resourceName)) {
        LogUtil.logInfo(LOG, _eventId, "Remove externalView for resource: " + resourceName);
        dataAccessor.removeProperty(keyBuilder.externalView(resourceName));
        externalviewsToRemove.add(resourceName);
      }
    }
    cache.removeExternalViews(externalviewsToRemove);
  } 
                            #location 32 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              @Override
  public void execute(final ClusterEvent event) throws Exception {
    _eventId = event.getEventId();
    HelixManager manager = event.getAttribute(AttributeName.helixmanager.name());
    Map<String, Resource> resourceMap = event.getAttribute(AttributeName.RESOURCES.name());
    ClusterDataCache cache = event.getAttribute(AttributeName.ClusterDataCache.name());

    if (manager == null || resourceMap == null || cache == null) {
      throw new StageException("Missing attributes in event:" + event
          + ". Requires ClusterManager|RESOURCES|DataCache");
    }

    HelixDataAccessor dataAccessor = manager.getHelixDataAccessor();
    PropertyKey.Builder keyBuilder = dataAccessor.keyBuilder();

    CurrentStateOutput currentStateOutput =
        event.getAttribute(AttributeName.CURRENT_STATE.name());
    ClusterStatusMonitor clusterStatusMonitor =
        event.getAttribute(AttributeName.clusterStatusMonitor.name());

    List<ExternalView> newExtViews = new ArrayList<>();
    Set<String> monitoringResources = new HashSet<>();

    Map<String, ExternalView> curExtViews = cache.getExternalViews();

    for (String resourceName : resourceMap.keySet()) {
      ExternalView view = new ExternalView(resourceName);
      // view.setBucketSize(currentStateOutput.getBucketSize(resourceName));
      // if resource ideal state has bucket size, set it
      // otherwise resource has been dropped, use bucket size from current state instead
      Resource resource = resourceMap.get(resourceName);
      if (resource.getBucketSize() > 0) {
        view.setBucketSize(resource.getBucketSize());
      } else {
        view.setBucketSize(currentStateOutput.getBucketSize(resourceName));
      }

      int totalPendingMessageCount = 0;

      for (Partition partition : resource.getPartitions()) {
        Map<String, String> currentStateMap =
            currentStateOutput.getCurrentStateMap(resourceName, partition);
        if (currentStateMap != null && currentStateMap.size() > 0) {
          // Set<String> disabledInstances
          // = cache.getDisabledInstancesForResource(resource.toString());
          for (String instance : currentStateMap.keySet()) {
            // if (!disabledInstances.contains(instance))
            // {
            view.setState(partition.getPartitionName(), instance, currentStateMap.get(instance));
            // }
          }
        }
        totalPendingMessageCount +=
            currentStateOutput.getPendingMessageMap(resource.getResourceName(), partition).size();
      }

      // Update cluster status monitor mbean
      IdealState idealState = cache.getIdealState(resourceName);
      if (!cache.isTaskCache()) {
        ResourceConfig resourceConfig = cache.getResourceConfig(resourceName);
        if (clusterStatusMonitor != null) {
          if (idealState != null // has ideal state
              && (resourceConfig == null || !resourceConfig.isMonitoringDisabled()) // monitoring not disabled
              && !idealState.getStateModelDefRef() // and not a job resource
              .equalsIgnoreCase(DefaultSchedulerMessageHandlerFactory.SCHEDULER_TASK_QUEUE)) {
            StateModelDefinition stateModelDef =
                cache.getStateModelDef(idealState.getStateModelDefRef());
            clusterStatusMonitor
                .setResourceStatus(view, cache.getIdealState(view.getResourceName()),
                    stateModelDef);
            clusterStatusMonitor
                .updatePendingMessages(resource.getResourceName(), totalPendingMessageCount);
            monitoringResources.add(resourceName);
          }
        }
      }
      ExternalView curExtView = curExtViews.get(resourceName);
      // copy simplefields from IS, in cases where IS is deleted copy it from existing ExternalView
      if (idealState != null) {
        view.getRecord().getSimpleFields().putAll(idealState.getRecord().getSimpleFields());
      } else if (curExtView != null) {
        view.getRecord().getSimpleFields().putAll(curExtView.getRecord().getSimpleFields());
      }

      // compare the new external view with current one, set only on different
      if (curExtView == null || !curExtView.getRecord().equals(view.getRecord())) {
        // Add external view to the list which will be written to ZK later.
        newExtViews.add(view);

        // For SCHEDULER_TASK_RESOURCE resource group (helix task queue), we need to find out which
        // task partitions are finished (COMPLETED or ERROR), update the status update of the original
        // scheduler message, and then remove the partitions from the ideal state
        if (idealState != null
            && idealState.getStateModelDefRef().equalsIgnoreCase(
            DefaultSchedulerMessageHandlerFactory.SCHEDULER_TASK_QUEUE)) {
          updateScheduledTaskStatus(view, manager, idealState);
        }
      }
    }

    // Keep MBeans for existing resources and unregister MBeans for dropped resources
    if (clusterStatusMonitor != null) {
      clusterStatusMonitor.retainResourceMonitor(monitoringResources);
    }

    List<String> externalViewsToRemove = new ArrayList<>();
    // TODO: consider not setting the externalview of SCHEDULER_TASK_QUEUE at all.
    // Are there any entity that will be interested in its change?

    // For the resource with DisableExternalView option turned on in IdealState
    // We will not actually create or write the externalView to ZooKeeper.
    List<PropertyKey> keys = new ArrayList<>();
    for(Iterator<ExternalView> it = newExtViews.iterator(); it.hasNext(); ) {
      ExternalView view = it.next();
      String resourceName = view.getResourceName();
      IdealState idealState = cache.getIdealState(resourceName);
      if (idealState != null && idealState.isExternalViewDisabled()) {
        it.remove();
        // remove the external view if the external view exists
        if (curExtViews.containsKey(resourceName)) {
          LogUtil
              .logInfo(LOG, _eventId, "Remove externalView for resource: " + resourceName);
          dataAccessor.removeProperty(keyBuilder.externalView(resourceName));
          externalViewsToRemove.add(resourceName);
        }
      } else {
        keys.add(keyBuilder.externalView(resourceName));
      }
    }

    // add/update external-views
    if (newExtViews.size() > 0) {
      dataAccessor.setChildren(keys, newExtViews);
      cache.updateExternalViews(newExtViews);
    }

    // remove dead external-views
    for (String resourceName : curExtViews.keySet()) {
      if (!resourceMap.keySet().contains(resourceName)) {
        LogUtil.logInfo(LOG, _eventId, "Remove externalView for resource: " + resourceName);
        dataAccessor.removeProperty(keyBuilder.externalView(resourceName));
        externalViewsToRemove.add(resourceName);
      }
    }
    cache.removeExternalViews(externalViewsToRemove);
  }