com.fitbur.mockito.objenesis.instantiator.basic.ProxyingInstantiator Maven / Gradle / Ivy
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/**
* 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 com.fitbur.mockito.objenesis.instantiator.basic;
import com.fitbur.mockito.objenesis.ObjenesisException;
import com.fitbur.mockito.objenesis.instantiator.ObjectInstantiator;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import static com.fitbur.mockito.objenesis.instantiator.basic.ClassDefinitionUtils.*;
/**
* This instantiator creates a class by dynamically extending it. It will skip the call to the parent constructor
* in the bytecode. So that the constructor is indeed not called but you however instantiate a child class, not
* the actual class. The class loader will normally throw a {@code VerifyError} is you do that. However, using
* {@code -Xverify:none} shoud make it work
*
* @author Henri Tremblay
*/
public class ProxyingInstantiator 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_CLASS = 7;
private static final int INDEX_UTF8_SUPERCLASS = 8;
private static int CONSTANT_POOL_COUNT = 9;
private static final byte[] CODE = { OPS_aload_0, OPS_return};
private static final int CODE_ATTRIBUTE_LENGTH = 12 + CODE.length;
private static final String SUFFIX = "$$$Objenesis";
private static final String CONSTRUCTOR_NAME = "";
private static final String CONSTRUCTOR_DESC = "()V";
private final Class newType;
public ProxyingInstantiator(Class type) {
byte[] classBytes = writeExtendingClass(type, SUFFIX);
try {
newType = ClassDefinitionUtils.defineClass(type.getName() + SUFFIX, classBytes, type.getClassLoader());
} catch (Exception e) {
throw new ObjenesisException(e);
}
}
@SuppressWarnings("unchecked")
public T newInstance() {
try {
return (T) newType.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 suffix the suffix appended to the class name to create the next extending class name
* @return the byte for the class
* @throws ObjenesisException is something goes wrong
*/
private static byte[] writeExtendingClass(Class type, String suffix) {
String parentClazz = classNameToInternalClassName(type.getName());
String clazz = parentClazz + suffix;
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_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(parentClazz);
// end of constant pool
// access flags: We want public, ACC_SUPER is always there
in.writeShort(ACC_PUBLIC | ACC_SUPER);
// 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(0);
// fields count (we have none)
in.writeShort(0);
// methods count (we have one: the default constructor)
in.writeShort(1);
// 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(CODE_ATTRIBUTE_LENGTH); // attribute length
in.writeShort(1); // max_stack
in.writeShort(1); // max_locals
in.writeInt(CODE.length); // code length
in.write(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();
}
}