@SuppressWarnings("unchecked")
 public void addDefaultValue(String className, JSONObject oper) throws Exception {
   ObjectMapper defaultValueMapper = ObjectMapperFactory.getOperatorValueSerializer();
   Class<? extends Operator> clazz = (Class<? extends Operator>) classLoader.loadClass(className);
   if (clazz != null) {
     Operator operIns = clazz.newInstance();
     String s = defaultValueMapper.writeValueAsString(operIns);
     oper.put("defaultValue", new JSONObject(s).get(className));
   }
 }
 public JSONObject describeClass(Class<?> clazz) throws Exception {
   JSONObject desc = new JSONObject();
   desc.put("name", clazz.getName());
   if (clazz.isEnum()) {
     @SuppressWarnings("unchecked")
     Class<Enum<?>> enumClass = (Class<Enum<?>>) clazz;
     ArrayList<String> enumNames = Lists.newArrayList();
     for (Enum<?> e : enumClass.getEnumConstants()) {
       enumNames.add(e.name());
     }
     desc.put("enum", enumNames);
   }
   UI_TYPE ui_type = UI_TYPE.getEnumFor(clazz);
   if (ui_type != null) {
     desc.put("uiType", ui_type.getName());
   }
   desc.put("properties", getClassProperties(clazz, 0));
   return desc;
 }
  private JSONArray getClassProperties(Class<?> clazz, int level) throws IntrospectionException {
    JSONArray arr = new JSONArray();
    TypeDiscoverer td = new TypeDiscoverer();
    try {
      for (PropertyDescriptor pd : Introspector.getBeanInfo(clazz).getPropertyDescriptors()) {
        Method readMethod = pd.getReadMethod();
        if (readMethod != null) {
          if (readMethod.getDeclaringClass() == java.lang.Enum.class) {
            // skip getDeclaringClass
            continue;
          } else if ("class".equals(pd.getName())) {
            // skip getClass
            continue;
          }
        } else {
          // yields com.datatorrent.api.Context on JDK6 and
          // com.datatorrent.api.Context.OperatorContext with JDK7
          if ("up".equals(pd.getName())
              && com.datatorrent.api.Context.class.isAssignableFrom(pd.getPropertyType())) {
            continue;
          }
        }
        // LOG.info("name: " + pd.getName() + " type: " + pd.getPropertyType());

        Class<?> propertyType = pd.getPropertyType();
        if (propertyType != null) {
          JSONObject propertyObj = new JSONObject();
          propertyObj.put("name", pd.getName());
          propertyObj.put("canGet", readMethod != null);
          propertyObj.put("canSet", pd.getWriteMethod() != null);
          if (readMethod != null) {
            for (Class<?> c = clazz; c != null; c = c.getSuperclass()) {
              OperatorClassInfo oci = classInfo.get(c.getName());
              if (oci != null) {
                MethodInfo getMethodInfo = oci.getMethods.get(readMethod.getName());
                if (getMethodInfo != null) {
                  addTagsToProperties(getMethodInfo, propertyObj);
                  break;
                }
              }
            }
            // type can be a type symbol or parameterized type
            td.setTypeArguments(clazz, readMethod.getGenericReturnType(), propertyObj);
          } else {
            if (pd.getWriteMethod() != null) {
              td.setTypeArguments(
                  clazz, pd.getWriteMethod().getGenericParameterTypes()[0], propertyObj);
            }
          }
          // if (!propertyType.isPrimitive() && !propertyType.isEnum() && !propertyType.isArray() &&
          // !propertyType.getName().startsWith("java.lang") && level < MAX_PROPERTY_LEVELS) {
          //  propertyObj.put("properties", getClassProperties(propertyType, level + 1));
          // }
          arr.put(propertyObj);
        }
      }
    } catch (JSONException ex) {
      throw new RuntimeException(ex);
    }
    return arr;
  }