1/*
2 * Copyright (C) 2012 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.caliper.json;
18
19import com.google.common.collect.ImmutableMap;
20import com.google.common.collect.Maps;
21import com.google.gson.Gson;
22import com.google.gson.TypeAdapter;
23import com.google.gson.TypeAdapterFactory;
24import com.google.gson.reflect.TypeToken;
25import com.google.gson.stream.JsonReader;
26import com.google.gson.stream.JsonWriter;
27
28import java.io.IOException;
29import java.lang.reflect.ParameterizedType;
30import java.lang.reflect.Type;
31import java.util.HashMap;
32import java.util.Map;
33
34/**
35 * Serializes and deserializes {@link ImmutableMap} instances using a {@link HashMap} as an
36 * intermediary.
37 */
38final class ImmutableMapTypeAdapterFactory implements TypeAdapterFactory {
39  @SuppressWarnings("unchecked")
40  @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
41    Type type = typeToken.getType();
42    if (typeToken.getRawType() != ImmutableMap.class
43        || !(type instanceof ParameterizedType)) {
44      return null;
45    }
46
47    com.google.common.reflect.TypeToken<ImmutableMap<?, ?>> betterToken =
48        (com.google.common.reflect.TypeToken<ImmutableMap<?, ?>>)
49            com.google.common.reflect.TypeToken.of(typeToken.getType());
50    final TypeAdapter<HashMap<?, ?>> hashMapAdapter =
51        (TypeAdapter<HashMap<?, ?>>) gson.getAdapter(
52            TypeToken.get(betterToken.getSupertype(Map.class).getSubtype(HashMap.class)
53                .getType()));
54    return new TypeAdapter<T>() {
55      @Override public void write(JsonWriter out, T value) throws IOException {
56        HashMap<?, ?> hashMap = Maps.newHashMap((Map<?, ?>) value);
57        hashMapAdapter.write(out, hashMap);
58      }
59
60      @Override public T read(JsonReader in) throws IOException {
61        HashMap<?, ?> hashMap = hashMapAdapter.read(in);
62        return (T) ImmutableMap.copyOf(hashMap);
63      }
64    };
65  }
66}
67