private List<PropertyProvider> ensurePropertyProviders(Type type) {
    synchronized (propertyProviders) {
      if (!propertyProviders.containsKey(type)) {
        List<PropertyProvider> providers = providerModule.getPropertyProviders(type);
        propertyProviders.put(type,
            providers == null ? Collections.emptyList() : providers);
      }
    }
    return propertyProviders.get(type);
  }
Get the list of property providers for the given type.

@param type  the resource type

@return the list of property providers
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/ClusterControllerImpl.java