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1 | /* | |
2 | * Copyright (C) 2011 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 | ||
17 | package com.google.gson.internal; | |
18 | ||
19 | import com.google.gson.InstanceCreator; | |
20 | import com.google.gson.JsonIOException; | |
21 | import com.google.gson.reflect.TypeToken; | |
22 | ||
23 | import java.lang.reflect.Constructor; | |
24 | import java.lang.reflect.InvocationTargetException; | |
25 | import java.lang.reflect.ParameterizedType; | |
26 | import java.lang.reflect.Type; | |
27 | import java.util.ArrayList; | |
28 | import java.util.Collection; | |
29 | import java.util.EnumSet; | |
30 | import java.util.LinkedHashMap; | |
31 | import java.util.LinkedHashSet; | |
32 | import java.util.LinkedList; | |
33 | import java.util.Map; | |
34 | import java.util.Queue; | |
35 | import java.util.Set; | |
36 | import java.util.SortedMap; | |
37 | import java.util.SortedSet; | |
38 | import java.util.TreeMap; | |
39 | import java.util.TreeSet; | |
40 | ||
41 | /** | |
42 | * Returns a function that can construct an instance of a requested type. | |
43 | */ | |
44 | public final class ConstructorConstructor { | |
45 | private final Map<Type, InstanceCreator<?>> instanceCreators; | |
46 | ||
47 | public ConstructorConstructor(Map<Type, InstanceCreator<?>> instanceCreators) { | |
48 | this.instanceCreators = instanceCreators; | |
49 | } | |
50 | ||
51 | public <T> ObjectConstructor<T> get(TypeToken<T> typeToken) { | |
52 | final Type type = typeToken.getType(); | |
53 | final Class<? super T> rawType = typeToken.getRawType(); | |
54 | ||
55 | // first try an instance creator | |
56 | ||
57 | @SuppressWarnings("unchecked") // types must agree | |
58 | final InstanceCreator<T> typeCreator = (InstanceCreator<T>) instanceCreators.get(type); | |
59 | if (typeCreator != null) { | |
60 | return new ObjectConstructor<T>() { | |
61 | public T construct() { | |
62 | return typeCreator.createInstance(type); | |
63 | } | |
64 | }; | |
65 | } | |
66 | ||
67 | // Next try raw type match for instance creators | |
68 | @SuppressWarnings("unchecked") // types must agree | |
69 | final InstanceCreator<T> rawTypeCreator = | |
70 | (InstanceCreator<T>) instanceCreators.get(rawType); | |
71 | if (rawTypeCreator != null) { | |
72 | return new ObjectConstructor<T>() { | |
73 | public T construct() { | |
74 | return rawTypeCreator.createInstance(type); | |
75 | } | |
76 | }; | |
77 | } | |
78 | ||
79 | ObjectConstructor<T> defaultConstructor = newDefaultConstructor(rawType); | |
80 | if (defaultConstructor != null) { | |
81 | return defaultConstructor; | |
82 | } | |
83 | ||
84 | ObjectConstructor<T> defaultImplementation = newDefaultImplementationConstructor(type, rawType); | |
85 | if (defaultImplementation != null) { | |
86 | return defaultImplementation; | |
87 | } | |
88 | ||
89 | // finally try unsafe | |
90 | return newUnsafeAllocator(type, rawType); | |
91 | } | |
92 | ||
93 | private <T> ObjectConstructor<T> newDefaultConstructor(Class<? super T> rawType) { | |
94 | try { | |
95 | final Constructor<? super T> constructor = rawType.getDeclaredConstructor(); | |
96 | if (!constructor.isAccessible()) { | |
97 | constructor.setAccessible(true); | |
98 | } | |
99 | return new ObjectConstructor<T>() { | |
100 | @SuppressWarnings("unchecked") // T is the same raw type as is requested | |
101 | public T construct() { | |
102 | try { | |
103 | Object[] args = null; | |
104 | return (T) constructor.newInstance(args); | |
105 | } catch (InstantiationException e) { | |
106 | // TODO: JsonParseException ? | |
107 | throw new RuntimeException("Failed to invoke " + constructor + " with no args", e); | |
108 | } catch (InvocationTargetException e) { | |
109 | // TODO: don't wrap if cause is unchecked! | |
110 | // TODO: JsonParseException ? | |
111 | throw new RuntimeException("Failed to invoke " + constructor + " with no args", | |
112 | e.getTargetException()); | |
113 | } catch (IllegalAccessException e) { | |
114 | throw new AssertionError(e); | |
115 | } | |
116 | } | |
117 | }; | |
118 | } catch (NoSuchMethodException e) { | |
119 | return null; | |
120 | } | |
121 | } | |
122 | ||
123 | /** | |
124 | * Constructors for common interface types like Map and List and their | |
125 | * subytpes. | |
126 | */ | |
127 | @SuppressWarnings("unchecked") // use runtime checks to guarantee that 'T' is what it is | |
128 | private <T> ObjectConstructor<T> newDefaultImplementationConstructor( | |
129 | final Type type, Class<? super T> rawType) { | |
130 | if (Collection.class.isAssignableFrom(rawType)) { | |
131 | if (SortedSet.class.isAssignableFrom(rawType)) { | |
132 | return new ObjectConstructor<T>() { | |
133 | public T construct() { | |
134 | return (T) new TreeSet<Object>(); | |
135 | } | |
136 | }; | |
137 | } else if (EnumSet.class.isAssignableFrom(rawType)) { | |
138 | return new ObjectConstructor<T>() { | |
139 | @SuppressWarnings("rawtypes") | |
140 | public T construct() { | |
141 | if (type instanceof ParameterizedType) { | |
142 | Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0]; | |
143 | if (elementType instanceof Class) { | |
144 | return (T) EnumSet.noneOf((Class)elementType); | |
145 | } else { | |
146 | throw new JsonIOException("Invalid EnumSet type: " + type.toString()); | |
147 | } | |
148 | } else { | |
149 | throw new JsonIOException("Invalid EnumSet type: " + type.toString()); | |
150 | } | |
151 | } | |
152 | }; | |
153 | } else if (Set.class.isAssignableFrom(rawType)) { | |
154 | return new ObjectConstructor<T>() { | |
155 | public T construct() { | |
156 | return (T) new LinkedHashSet<Object>(); | |
157 | } | |
158 | }; | |
159 | } else if (Queue.class.isAssignableFrom(rawType)) { | |
160 | return new ObjectConstructor<T>() { | |
161 | public T construct() { | |
162 | return (T) new LinkedList<Object>(); | |
163 | } | |
164 | }; | |
165 | } else { | |
166 | return new ObjectConstructor<T>() { | |
167 | public T construct() { | |
168 | return (T) new ArrayList<Object>(); | |
169 | } | |
170 | }; | |
171 | } | |
172 | } | |
173 | ||
174 | if (Map.class.isAssignableFrom(rawType)) { | |
175 | if (SortedMap.class.isAssignableFrom(rawType)) { | |
176 | return new ObjectConstructor<T>() { | |
177 | public T construct() { | |
178 | return (T) new TreeMap<Object, Object>(); | |
179 | } | |
180 | }; | |
181 | } else if (type instanceof ParameterizedType && !(String.class.isAssignableFrom( | |
182 | TypeToken.get(((ParameterizedType) type).getActualTypeArguments()[0]).getRawType()))) { | |
183 | return new ObjectConstructor<T>() { | |
184 | public T construct() { | |
185 | return (T) new LinkedHashMap<Object, Object>(); | |
186 | } | |
187 | }; | |
188 | } else { | |
189 | return new ObjectConstructor<T>() { | |
190 | public T construct() { | |
191 | return (T) new LinkedTreeMap<String, Object>(); | |
192 | } | |
193 | }; | |
194 | } | |
195 | } | |
196 | ||
197 | return null; | |
198 | } | |
199 | ||
200 | private <T> ObjectConstructor<T> newUnsafeAllocator( | |
201 | final Type type, final Class<? super T> rawType) { | |
202 | return new ObjectConstructor<T>() { | |
203 | private final UnsafeAllocator unsafeAllocator = UnsafeAllocator.create(); | |
204 | @SuppressWarnings("unchecked") | |
205 | public T construct() { | |
206 | try { | |
207 | Object newInstance = unsafeAllocator.newInstance(rawType); | |
208 | return (T) newInstance; | |
209 | } catch (Exception e) { | |
210 | throw new RuntimeException(("Unable to invoke no-args constructor for " + type + ". " | |
211 | + "Register an InstanceCreator with Gson for this type may fix this problem."), e); | |
212 | } | |
213 | } | |
214 | }; | |
215 | } | |
216 | ||
217 | @Override public String toString() { | |
218 | return instanceCreators.toString(); | |
219 | } | |
220 | } |