retransform-conflict-demo

Demonstration codes of an re-transform agent, which can't work with the SkyWalking version < 8.1

Test instruction

This application dynamically attaches a java agent through ByteBuddy, obtains the Instrumentation object, and calls the instrumentation.retransformClasses() to obtain the bytecode of target class.
The project is copied from this demo, with some modifications.

	public static void reTransform(Instrumentation instrumentation) throws UnmodifiableClassException {
		ClassFileTransformer transformer = new ClassFileTransformer() {
			@Override
			public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
					ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
				return null;
			}
		};
		try {
			instrumentation.addTransformer(transformer, true);

			try {
				instrumentation.retransformClasses(TestController.class);
			} catch (Throwable e) {
				e.printStackTrace();
			}

		} finally {
			instrumentation.removeTransformer(transformer);
		}

	}

Run without SkyWalking agent

before retransform:
com.example.demo.TestController

retransform:

after retransform:
com.example.demo.TestController

check retransform classes:
retransform classes successful.

Run with SkyWalking agent

java -javaagent:/apache-skywalking-apm-bin/agent/skywalking-agent.jar -jar retransform-conflict-demo.jar

before retransform:
com.example.demo.TestController$auxiliary$ckZJlKPI
com.example.demo.TestController
com.example.demo.TestController$auxiliary$DNtevU4I

retransform:
java.lang.ClassFormatError
        at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
        at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:167)
        at com.example.demo.DemoApplication.reTransform(DemoApplication.java:69)
        at com.example.demo.DemoApplication.main(DemoApplication.java:30)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:566)
        at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49)
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:109)
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:58)
        at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88)

after retransform:
com.example.demo.TestController$auxiliary$twNcBbRq
com.example.demo.TestController$auxiliary$ckZJlKPI
com.example.demo.TestController
com.example.demo.TestController$auxiliary$DNtevU4I

check retransform classes:
retransform classes not equal.

Run with SkyWalking agent and enable class cache feature

java -Dskywalking.agent.is_cache_enhanced_class=true -javaagent:/apache-skywalking-apm-bin/agent/skywalking-agent.jar -jar retransform-conflict-demo.jar

before retransform:
com.example.demo.TestController$auxiliary$lNjbfE8J
com.example.demo.TestController
com.example.demo.TestController$auxiliary$vmhaXoD8

retransform:

after retransform:
com.example.demo.TestController$auxiliary$lNjbfE8J
com.example.demo.TestController
com.example.demo.TestController$auxiliary$vmhaXoD8

check retransform classes:
retransform classes successful.