[英]Custom Classloader And Java Agent
I want to modifly the class in app which is running. 我想修改正在运行的应用程序中的类。 So I use java agent to do this.
因此,我使用Java代理来执行此操作。 My java code like this:
我的java代码是这样的:
/**
*
* @param args
* @param inst
*/
public static void agentmain(String args, Instrumentation inst) {
try {
inst.addTransformer(new GameClassFileTransformer(), true);
parseFiles();
List<Class<?>> retransformClasses = new ArrayList<>();
for (JarClassInfo jarClassInfo : GameAgentMain.bugFiles.values()) {
retransformClasses.add(Class.forName(jarClassInfo.getClassName()));
}
Class<?>[] classes = new Class[retransformClasses.size()];
retransformClasses.toArray(classes);
inst.retransformClasses(classes);
} catch (Exception e) {
LogUtil.error(e);
}
}
The JarClassInfo is a class about the class I want to reload.There hava two fields in JarClassInfo ,first is className,second is bytecode(java type is byte[]),The classname is which class want to reload.But the class is loaded by JarClassInfo是有关我要重新加载的类的类。JarClassInfo中有两个字段,第一个是className,第二个是字节码(java类型是byte []),该类名是要重新加载的类。但是要加载该类通过
custom classLoad
自定义classLoad
.When the app run at : 当应用在以下位置运行时:
retransformClasses.add(Class.forName(jarClassInfo.getClassName()));
retransformClasses.add(的Class.forName(jarClassInfo.getClassName()));
That is a exception be thrown: 这是一个例外:
Exception in thread "Attach Listener" java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:382) at sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:407) Caused by: java.lang.ClassFormatError: Incompatible magic value 2329931675 in class file com/jingqi/game/module/chat/command/SendChatMsgCMD at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:800) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$1(URLClassLoader.java:409) at java.net.URLClassLoader$2.run(URLClassLoader.java:361) at java.net.URLClassLoader$2.run(URLClassLoader.java:1) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:425) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:358) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:190) at com.jingqi.game.agent.GameAgentMain.agentmain(GameAgentMain.java:60) ... 6 more
My custom classloader(EncrypClassLoader) is used to decode my class. 我的自定义类加载器(EncrypClassLoader)用于解码我的类。 So the methd call stack indicate sun.misc.Launcher$AppClassLoader to load SendChatMsgCMD .The SendChatMsgCMD is not a normal class file(because I encrypt this class file).
因此,方法调用堆栈指示sun.misc.Launcher $ AppClassLoader加载SendChatMsgCMD .SendChatMsgCMD不是普通的类文件(因为我加密了该类文件)。
So ,what method can be solved 。 那么,什么方法可以解决。
Your custom classloader isn't doing what it's supposed to do: decrypt classes. 您的自定义类加载器没有执行应做的事情:解密类。
That's why you're getting the java.lang.ClassFormatError
about the invalid magic value. 这就是为什么您会收到有关无效魔术值的
java.lang.ClassFormatError
的原因。
EDIT: you need to also realise that Class.forName()
will load the class referred by the classname argument using the current class's classloader. 编辑:您还需要意识到
Class.forName()
将使用当前类的类加载器加载由类名参数引用的类。
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