| 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 java.io.ObjectInputStream; |
| 20 | import java.io.ObjectStreamClass; |
| 21 | import java.lang.reflect.Field; |
| 22 | import java.lang.reflect.Method; |
| 23 | |
| 24 | /** |
| 25 | * Do sneaky things to allocate objects without invoking their constructors. |
| 26 | * |
| 27 | * @author Joel Leitch |
| 28 | * @author Jesse Wilson |
| 29 | */ |
| 30 | public abstract class UnsafeAllocator { |
| 31 | public abstract <T> T newInstance(Class<T> c) throws Exception; |
| 32 | |
| 33 | public static UnsafeAllocator create() { |
| 34 | // try JVM |
| 35 | // public class Unsafe { |
| 36 | // public Object allocateInstance(Class<?> type); |
| 37 | // } |
| 38 | try { |
| 39 | Class<?> unsafeClass = Class.forName("sun.misc.Unsafe"); |
| 40 | Field f = unsafeClass.getDeclaredField("theUnsafe"); |
| 41 | f.setAccessible(true); |
| 42 | final Object unsafe = f.get(null); |
| 43 | final Method allocateInstance = unsafeClass.getMethod("allocateInstance", Class.class); |
| 44 | return new UnsafeAllocator() { |
| 45 | @Override |
| 46 | @SuppressWarnings("unchecked") |
| 47 | public <T> T newInstance(Class<T> c) throws Exception { |
| 48 | return (T) allocateInstance.invoke(unsafe, c); |
| 49 | } |
| 50 | }; |
| 51 | } catch (Exception ignored) { |
| 52 | } |
| 53 | |
| 54 | // try dalvikvm, pre-gingerbread |
| 55 | // public class ObjectInputStream { |
| 56 | // private static native Object newInstance( |
| 57 | // Class<?> instantiationClass, Class<?> constructorClass); |
| 58 | // } |
| 59 | try { |
| 60 | final Method newInstance = ObjectInputStream.class |
| 61 | .getDeclaredMethod("newInstance", Class.class, Class.class); |
| 62 | newInstance.setAccessible(true); |
| 63 | return new UnsafeAllocator() { |
| 64 | @Override |
| 65 | @SuppressWarnings("unchecked") |
| 66 | public <T> T newInstance(Class<T> c) throws Exception { |
| 67 | return (T) newInstance.invoke(null, c, Object.class); |
| 68 | } |
| 69 | }; |
| 70 | } catch (Exception ignored) { |
| 71 | } |
| 72 | |
| 73 | // try dalvikvm, post-gingerbread |
| 74 | // public class ObjectStreamClass { |
| 75 | // private static native int getConstructorId(Class<?> c); |
| 76 | // private static native Object newInstance(Class<?> instantiationClass, int methodId); |
| 77 | // } |
| 78 | try { |
| 79 | Method getConstructorId = ObjectStreamClass.class |
| 80 | .getDeclaredMethod("getConstructorId", Class.class); |
| 81 | getConstructorId.setAccessible(true); |
| 82 | final int constructorId = (Integer) getConstructorId.invoke(null, Object.class); |
| 83 | final Method newInstance = ObjectStreamClass.class |
| 84 | .getDeclaredMethod("newInstance", Class.class, int.class); |
| 85 | newInstance.setAccessible(true); |
| 86 | return new UnsafeAllocator() { |
| 87 | @Override |
| 88 | @SuppressWarnings("unchecked") |
| 89 | public <T> T newInstance(Class<T> c) throws Exception { |
| 90 | return (T) newInstance.invoke(null, c, constructorId); |
| 91 | } |
| 92 | }; |
| 93 | } catch (Exception ignored) { |
| 94 | } |
| 95 | |
| 96 | // give up |
| 97 | return new UnsafeAllocator() { |
| 98 | @Override |
| 99 | public <T> T newInstance(Class<T> c) { |
| 100 | throw new UnsupportedOperationException("Cannot allocate " + c); |
| 101 | } |
| 102 | }; |
| 103 | } |
| 104 | } |