| /* |
| * Copyright (C) 2011 Google Inc. |
| * |
| * Licensed 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 com.google.gson.internal; |
| |
| import java.io.ObjectInputStream; |
| import java.io.ObjectStreamClass; |
| import java.lang.reflect.Field; |
| import java.lang.reflect.Method; |
| import java.lang.reflect.Modifier; |
| |
| /** |
| * Do sneaky things to allocate objects without invoking their constructors. |
| * |
| * @author Joel Leitch |
| * @author Jesse Wilson |
| */ |
| public abstract class UnsafeAllocator { |
| public abstract <T> T newInstance(Class<T> c) throws Exception; |
| |
| /** |
| * Check if the class can be instantiated by Unsafe allocator. If the instance has interface or abstract modifiers |
| * return an exception message. |
| * @param c instance of the class to be checked |
| * @return if instantiable {@code null}, else a non-{@code null} exception message |
| */ |
| static String checkInstantiable(Class<?> c) { |
| int modifiers = c.getModifiers(); |
| if (Modifier.isInterface(modifiers)) { |
| return "Interfaces can't be instantiated! Register an InstanceCreator " |
| + "or a TypeAdapter for this type. Interface name: " + c.getName(); |
| } |
| if (Modifier.isAbstract(modifiers)) { |
| return "Abstract classes can't be instantiated! Register an InstanceCreator " |
| + "or a TypeAdapter for this type. Class name: " + c.getName(); |
| } |
| return null; |
| } |
| |
| /** |
| * Asserts that the class is instantiable. This check should have already occurred |
| * in {@link ConstructorConstructor}; this check here acts as safeguard since trying |
| * to use Unsafe for non-instantiable classes might crash the JVM on some devices. |
| */ |
| private static void assertInstantiable(Class<?> c) { |
| String exceptionMessage = checkInstantiable(c); |
| if (exceptionMessage != null) { |
| throw new AssertionError("UnsafeAllocator is used for non-instantiable type: " + exceptionMessage); |
| } |
| } |
| |
| public static UnsafeAllocator create() { |
| // try JVM |
| // public class Unsafe { |
| // public Object allocateInstance(Class<?> type); |
| // } |
| try { |
| Class<?> unsafeClass = Class.forName("sun.misc.Unsafe"); |
| Field f = unsafeClass.getDeclaredField("theUnsafe"); |
| f.setAccessible(true); |
| final Object unsafe = f.get(null); |
| final Method allocateInstance = unsafeClass.getMethod("allocateInstance", Class.class); |
| return new UnsafeAllocator() { |
| @Override |
| @SuppressWarnings("unchecked") |
| public <T> T newInstance(Class<T> c) throws Exception { |
| assertInstantiable(c); |
| return (T) allocateInstance.invoke(unsafe, c); |
| } |
| }; |
| } catch (Exception ignored) { |
| } |
| |
| // try dalvikvm, post-gingerbread |
| // public class ObjectStreamClass { |
| // private static native int getConstructorId(Class<?> c); |
| // private static native Object newInstance(Class<?> instantiationClass, int methodId); |
| // } |
| try { |
| Method getConstructorId = ObjectStreamClass.class |
| .getDeclaredMethod("getConstructorId", Class.class); |
| getConstructorId.setAccessible(true); |
| final int constructorId = (Integer) getConstructorId.invoke(null, Object.class); |
| final Method newInstance = ObjectStreamClass.class |
| .getDeclaredMethod("newInstance", Class.class, int.class); |
| newInstance.setAccessible(true); |
| return new UnsafeAllocator() { |
| @Override |
| @SuppressWarnings("unchecked") |
| public <T> T newInstance(Class<T> c) throws Exception { |
| assertInstantiable(c); |
| return (T) newInstance.invoke(null, c, constructorId); |
| } |
| }; |
| } catch (Exception ignored) { |
| } |
| |
| // try dalvikvm, pre-gingerbread |
| // public class ObjectInputStream { |
| // private static native Object newInstance( |
| // Class<?> instantiationClass, Class<?> constructorClass); |
| // } |
| try { |
| final Method newInstance = ObjectInputStream.class |
| .getDeclaredMethod("newInstance", Class.class, Class.class); |
| newInstance.setAccessible(true); |
| return new UnsafeAllocator() { |
| @Override |
| @SuppressWarnings("unchecked") |
| public <T> T newInstance(Class<T> c) throws Exception { |
| assertInstantiable(c); |
| return (T) newInstance.invoke(null, c, Object.class); |
| } |
| }; |
| } catch (Exception ignored) { |
| } |
| |
| // give up |
| return new UnsafeAllocator() { |
| @Override |
| public <T> T newInstance(Class<T> c) { |
| throw new UnsupportedOperationException("Cannot allocate " + c + ". Usage of JDK sun.misc.Unsafe is enabled, " |
| + "but it could not be used. Make sure your runtime is configured correctly."); |
| } |
| }; |
| } |
| } |