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.ImmutableSet;
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.Map;
32import java.util.SortedMap;
33import java.util.TreeMap;
34
35/**
36 * Serializes and deserializes {@link SortedMap} instances using a {@link TreeMap} with natural
37 * ordering as an intermediary.
38 */
39final class NaturallySortedMapTypeAdapterFactory implements TypeAdapterFactory {
40  @SuppressWarnings("rawtypes")
41  private static final ImmutableSet<Class<? extends SortedMap>> CLASSES =
42      ImmutableSet.of(SortedMap.class, TreeMap.class);
43
44  @SuppressWarnings("unchecked")
45  @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
46    Type type = typeToken.getType();
47    if (!CLASSES.contains(typeToken.getRawType())
48        || !(type instanceof ParameterizedType)) {
49      return null;
50    }
51
52    com.google.common.reflect.TypeToken<SortedMap<?, ?>> betterToken =
53        (com.google.common.reflect.TypeToken<SortedMap<?, ?>>)
54            com.google.common.reflect.TypeToken.of(typeToken.getType());
55    final TypeAdapter<Map<?, ?>> mapAdapter =
56        (TypeAdapter<Map<?, ?>>) gson.getAdapter(
57            TypeToken.get(betterToken.getSupertype(Map.class).getType()));
58    return new TypeAdapter<T>() {
59      @Override public void write(JsonWriter out, T value) throws IOException {
60        TreeMap<?, ?> treeMap = Maps.newTreeMap((SortedMap<?, ?>) value);
61        mapAdapter.write(out, treeMap);
62      }
63
64      @SuppressWarnings("rawtypes")
65      @Override public T read(JsonReader in) throws IOException {
66        TreeMap treeMap = Maps.newTreeMap();
67        treeMap.putAll(mapAdapter.read(in));
68        return (T) treeMap;
69      }
70    };
71  }
72}
73