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A library for instantiating Java objects
/**
* Copyright 2006-2016 the original author or 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 org.objenesis.instantiator.sun;
import org.objenesis.ObjenesisException;
import org.objenesis.instantiator.ObjectInstantiator;
import org.objenesis.instantiator.basic.ClassDefinitionUtils;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import static org.objenesis.instantiator.basic.ClassDefinitionUtils.*;
/**
* This instantiator will correctly bypass the constructors by instantiating the class using the default
* constructor from Object. It will be allowed to do so by extending {@code MagicAccessorImpl} which prevents
* its children to be verified by the class loader
*
* @author Henri Tremblay
*/
public class MagicInstantiator implements ObjectInstantiator {
private static final int INDEX_CLASS_THIS = 1;
private static final int INDEX_CLASS_SUPERCLASS = 2;
private static final int INDEX_UTF8_CONSTRUCTOR_NAME = 3;
private static final int INDEX_UTF8_CONSTRUCTOR_DESC = 4;
private static final int INDEX_UTF8_CODE_ATTRIBUTE = 5;
private static final int INDEX_UTF8_INSTANTIATOR_CLASS = 7;
private static final int INDEX_UTF8_SUPERCLASS = 8;
private static final int INDEX_CLASS_INTERFACE = 9;
private static final int INDEX_UTF8_INTERFACE = 10;
private static final int INDEX_UTF8_NEWINSTANCE_NAME = 11;
private static final int INDEX_UTF8_NEWINSTANCE_DESC = 12;
private static final int INDEX_METHODREF_OBJECT_CONSTRUCTOR = 13;
private static final int INDEX_CLASS_OBJECT = 14;
private static final int INDEX_UTF8_OBJECT = 15;
private static final int INDEX_NAMEANDTYPE_DEFAULT_CONSTRUCTOR = 16;
private static final int INDEX_CLASS_TYPE = 17;
private static final int INDEX_UTF8_TYPE = 18;
private static int CONSTANT_POOL_COUNT = 19;
private static final byte[] CONSTRUCTOR_CODE = { OPS_aload_0, OPS_invokespecial, 0, INDEX_METHODREF_OBJECT_CONSTRUCTOR, OPS_return};
private static final int CONSTRUCTOR_CODE_ATTRIBUTE_LENGTH = 12 + CONSTRUCTOR_CODE.length;
private static final byte[] NEWINSTANCE_CODE = { OPS_new, 0, INDEX_CLASS_TYPE, OPS_dup, OPS_invokespecial, 0, INDEX_METHODREF_OBJECT_CONSTRUCTOR, OPS_areturn};
private static final int NEWINSTANCE_CODE_ATTRIBUTE_LENGTH = 12 + NEWINSTANCE_CODE.length;
private static final String CONSTRUCTOR_NAME = "";
private static final String CONSTRUCTOR_DESC = "()V";
private ObjectInstantiator instantiator;
public MagicInstantiator(Class type) {
instantiator = newInstantiatorOf(type);
}
private ObjectInstantiator newInstantiatorOf(Class type) {
String suffix = type.getSimpleName();
String className = getClass().getName() + "$$$" + suffix;
Class> clazz = getExistingClass(getClass().getClassLoader(), className);
if(clazz == null) {
byte[] classBytes = writeExtendingClass(type, className);
try {
clazz = ClassDefinitionUtils.defineClass(className, classBytes, getClass().getClassLoader());
} catch (Exception e) {
throw new ObjenesisException(e);
}
}
try {
return clazz.newInstance();
} catch (InstantiationException e) {
throw new ObjenesisException(e);
} catch (IllegalAccessException e) {
throw new ObjenesisException(e);
}
}
/**
* Will generate the bytes for a class extending the type passed in parameter. This class will
* only have an empty default constructor
*
* @param type type to extend
* @param className name of the wrapped instantiator class
* @return the byte for the class
* @throws ObjenesisException is something goes wrong
*/
private byte[] writeExtendingClass(Class type, String className) {
String clazz = classNameToInternalClassName(className);
DataOutputStream in = null;
ByteArrayOutputStream bIn = new ByteArrayOutputStream(1000); // 1000 should be large enough to fit the entire class
try {
in = new DataOutputStream(bIn);
in.write(MAGIC);
in.write(VERSION);
in.writeShort(CONSTANT_POOL_COUNT);
// set all the constant pool here
// 1. class
in.writeByte(CONSTANT_Class);
in.writeShort(INDEX_UTF8_INSTANTIATOR_CLASS);
// 2. super class
in.writeByte(CONSTANT_Class);
in.writeShort(INDEX_UTF8_SUPERCLASS);
// 3. default constructor name
in.writeByte(CONSTANT_Utf8);
in.writeUTF(CONSTRUCTOR_NAME);
// 4. default constructor description
in.writeByte(CONSTANT_Utf8);
in.writeUTF(CONSTRUCTOR_DESC);
// 5. Code
in.writeByte(CONSTANT_Utf8);
in.writeUTF("Code");
// 6. Class name
in.writeByte(CONSTANT_Utf8);
in.writeUTF("L" + clazz + ";");
// 7. Class name (again)
in.writeByte(CONSTANT_Utf8);
in.writeUTF(clazz);
// 8. Superclass name
in.writeByte(CONSTANT_Utf8);
// in.writeUTF("java/lang/Object");
in.writeUTF("sun/reflect/MagicAccessorImpl");
// 9. ObjectInstantiator interface
in.writeByte(CONSTANT_Class);
in.writeShort(INDEX_UTF8_INTERFACE);
// 10. ObjectInstantiator name
in.writeByte(CONSTANT_Utf8);
in.writeUTF(ObjectInstantiator.class.getName().replace('.', '/'));
// 11. newInstance name
in.writeByte(CONSTANT_Utf8);
in.writeUTF("newInstance");
// 12. newInstance desc
in.writeByte(CONSTANT_Utf8);
in.writeUTF("()Ljava/lang/Object;");
// 13. Methodref to the Object constructor
in.writeByte(CONSTANT_Methodref);
in.writeShort(INDEX_CLASS_OBJECT);
in.writeShort(INDEX_NAMEANDTYPE_DEFAULT_CONSTRUCTOR);
// 14. Object class
in.writeByte(CONSTANT_Class);
in.writeShort(INDEX_UTF8_OBJECT);
// 15. Object class name
in.writeByte(CONSTANT_Utf8);
in.writeUTF("java/lang/Object");
// 16. Default constructor name and type
in.writeByte(CONSTANT_NameAndType);
in.writeShort(INDEX_UTF8_CONSTRUCTOR_NAME);
in.writeShort(INDEX_UTF8_CONSTRUCTOR_DESC);
// 17. Type to instantiate class
in.writeByte(CONSTANT_Class);
in.writeShort(INDEX_UTF8_TYPE);
// 18. Type to instantiate name
in.writeByte(CONSTANT_Utf8);
in.writeUTF(classNameToInternalClassName(type.getName()));
// end of constant pool
// access flags: We want public, ACC_SUPER is always there
in.writeShort(ACC_PUBLIC | ACC_SUPER | ACC_FINAL);
// this class index in the constant pool
in.writeShort(INDEX_CLASS_THIS);
// super class index in the constant pool
in.writeShort(INDEX_CLASS_SUPERCLASS);
// interfaces implemented count (we have none)
in.writeShort(1);
in.writeShort(INDEX_CLASS_INTERFACE);
// fields count (we have none)
in.writeShort(0);
// method count (we have two: the default constructor and newInstance)
in.writeShort(2);
// default constructor method_info
in.writeShort(ACC_PUBLIC);
in.writeShort(INDEX_UTF8_CONSTRUCTOR_NAME); // index of the method name ()
in.writeShort(INDEX_UTF8_CONSTRUCTOR_DESC); // index of the description
in.writeShort(1); // number of attributes: only one, the code
// code attribute of the default constructor
in.writeShort(INDEX_UTF8_CODE_ATTRIBUTE);
in.writeInt(CONSTRUCTOR_CODE_ATTRIBUTE_LENGTH); // attribute length
in.writeShort(0); // max_stack
in.writeShort(1); // max_locals
in.writeInt(CONSTRUCTOR_CODE.length); // code length
in.write(CONSTRUCTOR_CODE);
in.writeShort(0); // exception_table_length = 0
in.writeShort(0); // attributes count = 0, no need to have LineNumberTable and LocalVariableTable
// newInstance method_info
in.writeShort(ACC_PUBLIC);
in.writeShort(INDEX_UTF8_NEWINSTANCE_NAME); // index of the method name (newInstance)
in.writeShort(INDEX_UTF8_NEWINSTANCE_DESC); // index of the description
in.writeShort(1); // number of attributes: only one, the code
// code attribute of newInstance
in.writeShort(INDEX_UTF8_CODE_ATTRIBUTE);
in.writeInt(NEWINSTANCE_CODE_ATTRIBUTE_LENGTH); // attribute length
in.writeShort(2); // max_stack
in.writeShort(1); // max_locals
in.writeInt(NEWINSTANCE_CODE.length); // code length
in.write(NEWINSTANCE_CODE);
in.writeShort(0); // exception_table_length = 0
in.writeShort(0); // attributes count = 0, no need to have LineNumberTable and LocalVariableTable
// class attributes
in.writeShort(0); // none. No need to have a source file attribute
} catch (IOException e) {
throw new ObjenesisException(e);
} finally {
if(in != null) {
try {
in.close();
} catch (IOException e) {
throw new ObjenesisException(e);
}
}
}
return bIn.toByteArray();
}
public T newInstance() {
return instantiator.newInstance();
}
}