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/*
* Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
import java.io.InputStream;
import java.lang.classfile.ClassElement;
import java.lang.classfile.ClassFile;
import java.lang.classfile.ClassModel;
import java.lang.constant.ClassDesc;
import java.lang.instrument.ClassDefinition;
import java.lang.instrument.Instrumentation;
import jdk.test.lib.compiler.InMemoryJavaCompiler;
import jdk.test.lib.helpers.ClassFileInstaller;
/*
* Helper class to write tests that redefine classes.
* When main method is run, it will create a redefineagent.jar that can be used
* with the -javaagent option to support redefining classes in jtreg tests.
*
* See sample test in test/testlibrary_tests/RedefineClassTest.java
*/
public class RedefineClassHelper {
public static Instrumentation instrumentation;
public static void premain(String agentArgs, Instrumentation inst) {
instrumentation = inst;
}
/**
* Redefine a class
*
* @param clazz Class to redefine
* @param javacode String with the new java code for the class to be redefined
*/
public static void redefineClass(Class<?> clazz, String javacode) throws Exception {
byte[] bytecode = InMemoryJavaCompiler.compile(clazz.getName(), javacode);
redefineClass(clazz, bytecode);
}
/**
* Redefine a class
*
* @param clazz Class to redefine
* @param bytecode byte[] with the new class
*/
public static void redefineClass(Class<?> clazz, byte[] bytecode) throws Exception {
instrumentation.redefineClasses(new ClassDefinition(clazz, bytecode));
}
private static byte[] getBytecodes(ClassLoader loader, String name) throws Exception {
try (InputStream is = loader.getResourceAsStream(name + ".class")) {
byte[] buf = is.readAllBytes();
System.out.println("sizeof(" + name + ".class) == " + buf.length);
return buf;
}
}
/*
* Copy the class defined by `bytes`, replacing the name of the class with `newClassName`,
* so that both old and new classes can be compiled by jtreg for the test.
*
* @param bytes read from the original class file.
* @param newClassName new class name for the returned class representation
* @return a copy of the class represented by `bytes` but with the name `newClassName`
*/
public static byte[] replaceClassName(byte[] bytes, String newClassName) throws Exception {
ClassModel classModel = ClassFile.of().parse(bytes);
return ClassFile.of().build(ClassDesc.of(newClassName), classModel::forEach);
}
/*
* Replace class name in bytecodes to the class we're trying to redefine, so that both
* old and new classes can be compiled with jtreg for the test.
*
* @param loader ClassLoader to find the bytes for the old class.
* @param oldClassName old class name.
* @param newClassName new class name to replace with old class name.
* @return a copy of the class represented by `bytes` but with the name `newClassName`
*/
public static byte[] replaceClassName(ClassLoader loader, String oldClassName, String newClassName) throws Exception {
byte[] buf = getBytecodes(loader, oldClassName);
return replaceClassName(buf, newClassName);
}
/**
* Main method to be invoked before test to create the redefineagent.jar
*/
public static void main(String[] args) throws Exception {
String manifest = "Premain-Class: RedefineClassHelper\nCan-Redefine-Classes: true\n";
ClassFileInstaller.writeJar("redefineagent.jar", ClassFileInstaller.Manifest.fromString(manifest), "RedefineClassHelper");
}
}
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