core/src/main/java/org/jclouds/json/internal/JsonObjectAsMap.java

/**
 * Licensed to jclouds, Inc. (jclouds) under one or more
 * contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  jclouds 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 org.jclouds.json.internal;

import java.lang.reflect.Field;
import java.util.Map;

import com.google.common.base.Function;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

/**
 * Exposes the JsonObject as a map so that we can use gauva apis on it.
 * http://code.google.com/p/google-gson/issues/detail?id=325
 * @author Adrian Cole
 */
public enum JsonObjectAsMap implements Function<JsonObject, Map<String, JsonElement>> {
   INSTANCE;

   private final Field members;

   JsonObjectAsMap() {
      try {
         members = JsonObject.class.getDeclaredField("members");
         members.setAccessible(true);
      } catch (NoSuchFieldException e) {
         throw new UnsupportedOperationException("cannot access gson internals", e);
      }
   }

   @SuppressWarnings("unchecked")
   @Override
   public Map<String, JsonElement> apply(JsonObject in) {
      try {
         return (Map<String, JsonElement>) members.get(in);
      } catch (IllegalArgumentException e) {
         throw new UnsupportedOperationException("cannot access gson internals", e);
      } catch (IllegalAccessException e) {
         throw new UnsupportedOperationException("cannot access gson internals", e);
      }
   }
}