Fix unsafe allocations on Android

gson/src/main/java/com/google/gson/MappedObjectConstructor.java

@@ -18,13 +18,7 @@ package com.google.gson;
 
 import java.lang.reflect.Array;
 import java.lang.reflect.Constructor;
-import java.lang.reflect.Field;
-import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Type;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-import sun.misc.Unsafe;
 
 /**
  * This class contains a mapping of all the application specific
@@ -37,8 +31,7 @@ import sun.misc.Unsafe;
  * @author Joel Leitch
  */
 final class MappedObjectConstructor implements ObjectConstructor {
-  private static final Logger log = Logger.getLogger(MappedObjectConstructor.class.getName());
-  private static final Unsafe THE_UNSAFE = getUnsafe();
+  private static final UnsafeAllocator unsafeAllocator = UnsafeAllocator.create();
 
   private final ParameterizedTypeHandlerMap<InstanceCreator<?>> instanceCreatorMap;
 
@@ -56,18 +49,6 @@ final class MappedObjectConstructor implements ObjectConstructor {
     return (T) constructWithNoArgConstructor(typeOfT);
   }
 
-  private static Unsafe getUnsafe() {
-    try {
-      Field f = Unsafe.class.getDeclaredField("theUnsafe");
-      f.setAccessible(true);
-      return (Unsafe) f.get(null);
-    } catch (NoSuchFieldException e) {
-      throw new Error();
-    } catch (IllegalAccessException e) {
-      throw new Error();
-    }
-  }
-
   public Object constructArray(Type type, int length) {
     return Array.newInstance(Types.getRawType(type), length);
   }
@@ -77,17 +58,10 @@ final class MappedObjectConstructor implements ObjectConstructor {
     try {
       Class<T> clazz = (Class<T>) Types.getRawType(typeOfT);
       Constructor<T> constructor = getNoArgsConstructor(clazz);
-      if (constructor == null) {
-        return (T) THE_UNSAFE.allocateInstance(clazz);
-      }
-      return constructor.newInstance();
-    } catch (InstantiationException e) {
-      throw new RuntimeException(("Unable to invoke no-args constructor for " + typeOfT + ". "
-          + "Register an InstanceCreator with Gson for this type may fix this problem."), e);
-    } catch (IllegalAccessException e) {
-      throw new RuntimeException(("Unable to invoke no-args constructor for " + typeOfT + ". "
-          + "Register an InstanceCreator with Gson for this type may fix this problem."), e);
-    } catch (InvocationTargetException e) {
+      return constructor == null
+          ? unsafeAllocator.newInstance(clazz)
+          : constructor.newInstance();
+    } catch (Exception e) {
       throw new RuntimeException(("Unable to invoke no-args constructor for " + typeOfT + ". "
           + "Register an InstanceCreator with Gson for this type may fix this problem."), e);
     }
@@ -103,20 +77,6 @@ final class MappedObjectConstructor implements ObjectConstructor {
     }
   }
 
-  /**
-   * Use this methods to register an {@link InstanceCreator} for a new type.
-   *
-   * @param <T> the type of class to be mapped with its "creator"
-   * @param typeOfT the instance type that will be created
-   * @param creator the {@link InstanceCreator} instance to register
-   */
-  <T> void register(Type typeOfT, InstanceCreator<? extends T> creator) {
-    if (instanceCreatorMap.hasSpecificHandlerFor(typeOfT)) {
-      log.log(Level.WARNING, "Overriding the existing InstanceCreator for {0}", typeOfT);
-    }
-    instanceCreatorMap.register(typeOfT, creator);
-  }
-  
   @Override
   public String toString() {
     return instanceCreatorMap.toString();

gson/src/main/java/com/google/gson/UnsafeAllocator.java

@@ -0,0 +1,100 @@
+/*
+ * 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;
+
+import java.io.ObjectInputStream;
+import java.io.ObjectStreamClass;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+
+/**
+ * Do sneaky things to allocate objects without invoking their constructors.
+ *
+ * @author Joel Leitch
+ * @author Jesse Wilson
+ */
+abstract class UnsafeAllocator {
+  public abstract <T> T newInstance(Class<T> c) throws Exception;
+
+  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() {
+        @SuppressWarnings("unchecked")
+        public <T> T newInstance(Class<T> c) throws Exception {
+          return (T) allocateInstance.invoke(unsafe, c);
+        }
+      };
+    } 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() {
+        @SuppressWarnings("unchecked")
+        public <T> T newInstance(Class<T> c) throws Exception {
+          return (T) newInstance.invoke(null, c, Object.class);
+        }
+      };
+    } catch (Exception ignored) {
+    }
+
+    // try dalvivkm, 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() {
+        @SuppressWarnings("unchecked")
+        public <T> T newInstance(Class<T> c) throws Exception {
+          return (T) newInstance.invoke(null, c, constructorId);
+        }
+      };
+    } catch (Exception ignored) {
+    }
+
+    // give up
+    return new UnsafeAllocator() {
+      public <T> T newInstance(Class<T> c) throws InstantiationException {
+        throw new UnsupportedOperationException("Cannot allocate " + c);
+      }
+    };
+  }
+}