/
UnsafeReflectionAccessor.java
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/
UnsafeReflectionAccessor.java
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/*
* Copyright (C) 2017 The Gson authors
*
* 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.reflect;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import com.google.gson.JsonIOException;
/**
* An implementation of {@link ReflectionAccessor} based on {@link Unsafe}.
* <p>
* NOTE: This implementation is designed for Java 9. Although it should work with earlier Java releases, it is better to
* use {@link PreJava9ReflectionAccessor} for them.
*/
@SuppressWarnings({"unchecked", "rawtypes"})
final class UnsafeReflectionAccessor extends ReflectionAccessor {
private static Class unsafeClass;
private final Object theUnsafe = getUnsafeInstance();
private final Field overrideField = getOverrideField();
/** {@inheritDoc} */
@Override
public void makeAccessible(AccessibleObject ao) {
boolean success = makeAccessibleWithUnsafe(ao);
if (!success) {
try {
// unsafe couldn't be found, so try using accessible anyway
ao.setAccessible(true);
} catch (SecurityException e) {
throw new JsonIOException("Gson couldn't modify fields for " + ao
+ "\nand sun.misc.Unsafe not found.\nEither write a custom type adapter,"
+ " or make fields accessible, or include sun.misc.Unsafe.", e);
}
}
}
// Visible for testing only
boolean makeAccessibleWithUnsafe(AccessibleObject ao) {
if (theUnsafe != null && overrideField != null) {
try {
Method method = unsafeClass.getMethod("objectFieldOffset", Field.class);
long overrideOffset = (Long) method.invoke(theUnsafe, overrideField); // long overrideOffset = theUnsafe.objectFieldOffset(overrideField);
Method putBooleanMethod = unsafeClass.getMethod("putBoolean", Object.class, long.class, boolean.class);
putBooleanMethod.invoke(theUnsafe, ao, overrideOffset, true); // theUnsafe.putBoolean(ao, overrideOffset, true);
return true;
} catch (Exception ignored) { // do nothing
}
}
return false;
}
private static Object getUnsafeInstance() {
try {
unsafeClass = Class.forName("sun.misc.Unsafe");
Field unsafeField = unsafeClass.getDeclaredField("theUnsafe");
unsafeField.setAccessible(true);
return unsafeField.get(null);
} catch (Exception e) {
return null;
}
}
private static Field getOverrideField() {
try {
return AccessibleObject.class.getDeclaredField("override");
} catch (Exception e) {
return null;
}
}
}