content: // Licensed to the Apache Software Foundation (ASF) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The ASF licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  package com.cloud.ovm.object;
  
  import java.lang.reflect.Type;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  
  import com.google.gson.Gson;
  import com.google.gson.GsonBuilder;
  import com.google.gson.JsonDeserializationContext;
  import com.google.gson.JsonDeserializer;
  import com.google.gson.JsonElement;
  import com.google.gson.JsonObject;
  import com.google.gson.JsonParseException;
  import com.google.gson.reflect.TypeToken;
  
  public class Coder {
      private static Gson s_gson;
      private static Gson s_mapGson;
  
      public static Object[] s_emptyParams = new Object[0];
  
      private static class MapDecoder implements JsonDeserializer<Map<String, String>> {
          @Override
          public Map<String, String> deserialize(JsonElement arg0, Type arg1, JsonDeserializationContext arg2) throws JsonParseException {
              if (!arg0.isJsonObject()) {
                  throw new JsonParseException(arg0.toString() + " is not Json Object, cannot convert to map");
              }
              JsonObject objs = arg0.getAsJsonObject();
              Map<String, String> map = new HashMap<String, String>();
              for (Entry<String, JsonElement> e : objs.entrySet()) {
                  if (!e.getValue().isJsonPrimitive()) {
                      throw new JsonParseException(e.getValue().toString() + " is not a Json primitive," + arg0 + " can not convert to map");
                  }
                  map.put(e.getKey(), e.getValue().getAsString());
              }
              return map;
          }
  
      }
  
      static {
          GsonBuilder _builder = new GsonBuilder();
          _builder.registerTypeAdapter(Map.class, new MapDecoder());
          s_mapGson = _builder.create();
          s_gson = new Gson();
      }
  
      public static String toJson(Object obj) {
          return s_gson.toJson(obj);
      }
  
      public static <T> T fromJson(String str, Class<T> clz) {
          return s_gson.fromJson(str, clz);
      }
  
      @SuppressWarnings("unchecked")
      public static Map<String, String> mapFromJson(String str) {
          return s_mapGson.fromJson(str, Map.class);
      }
  
      public static List<String> listFromJson(String str) {
          Type listType = new TypeToken<List<String>>() {
          }.getType();
          return s_gson.fromJson(str, listType);
      }
  }
  