com.squareup.moshi.ClassFactory Maven / Gradle / Ivy
/*
* 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.squareup.moshi;
import com.squareup.moshi.internal.Util;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
* Magic that creates instances of arbitrary concrete classes. Derived from Gson's UnsafeAllocator
* and ConstructorConstructor classes.
*
* @author Joel Leitch
* @author Jesse Wilson
*/
abstract class ClassFactory {
abstract T newInstance() throws
InvocationTargetException, IllegalAccessException, InstantiationException;
public static ClassFactory get(final Class rawType) {
// Try to find a no-args constructor. May be any visibility including private.
try {
final Constructor constructor = rawType.getDeclaredConstructor();
constructor.setAccessible(true);
return new ClassFactory() {
@SuppressWarnings("unchecked") // T is the same raw type as is requested
@Override
public T newInstance() throws IllegalAccessException, InvocationTargetException,
InstantiationException {
Object[] args = null;
return (T) constructor.newInstance(args);
}
@Override
public String toString() {
return rawType.getName();
}
};
} catch (NoSuchMethodException ignored) {
// No no-args constructor. Fall back to something more magical...
}
// Try the JVM's Unsafe mechanism.
// 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 ClassFactory() {
@SuppressWarnings("unchecked")
@Override
public T newInstance() throws InvocationTargetException, IllegalAccessException {
return (T) allocateInstance.invoke(unsafe, rawType);
}
@Override
public String toString() {
return rawType.getName();
}
};
} catch (IllegalAccessException e) {
throw new AssertionError();
} catch (ClassNotFoundException e) {
} catch (NoSuchMethodException e) {
} catch (NoSuchFieldException e) {
}
// Try (post-Gingerbread) Dalvik/libcore's ObjectStreamClass mechanism.
// 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 ClassFactory() {
@SuppressWarnings("unchecked")
@Override
public T newInstance() throws InvocationTargetException, IllegalAccessException {
return (T) newInstance.invoke(null, rawType, constructorId);
}
@Override
public String toString() {
return rawType.getName();
}
};
} catch (IllegalAccessException e) {
throw new AssertionError();
} catch (InvocationTargetException e) {
throw Util.rethrowCause(e);
} catch (NoSuchMethodException ignored) {
// Not the expected version of Dalvik/libcore!
}
// Try (pre-Gingerbread) Dalvik/libcore's ObjectInputStream mechanism.
// 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 ClassFactory() {
@SuppressWarnings("unchecked")
@Override
public T newInstance() throws InvocationTargetException, IllegalAccessException {
return (T) newInstance.invoke(null, rawType, Object.class);
}
@Override
public String toString() {
return rawType.getName();
}
};
} catch (Exception ignored) {
}
throw new IllegalArgumentException("cannot construct instances of " + rawType.getName());
}
}