Class not found exception LogginAdvice

Hi, I am loading an Advice Class using URLClassLoader, but the app is throwing a ClassNotFound Exception exception wheneve I am using a class variable inside the function.

Agent :

Class<?> testClass=null;;
		try {
			testClass = Class.forName("com.exp.LoggingAdvice", true, classLoader);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		System.out.println("Class = "+testClass.getCanonicalName());
		return new AgentBuilder.Default().disableClassFormatChanges()
				.with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
				.with(AgentBuilder.RedefinitionStrategy.REDEFINITION)
	            .with(AgentBuilder.TypeStrategy.Default.REDEFINE)
	            .type(ElementMatchers.hasSuperType(named(className)))
	            .transform(new AgentBuilder.Transformer.ForAdvice()
                        .include(classLoader)
                        .advice(named(methodName), testClass.getName())
                );

Output:

`Class = com.exp.LoggingAdvice

2019-07-25 13:10:41.932 INFO 17674 — [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet ‘dispatcherServlet’ 2019-07-25 13:10:41.933 INFO 17674 — [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet ‘dispatcherServlet’ 2019-07-25 13:10:42.036 INFO 17674 — [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 102 ms LOL 2019-07-25 13:10:42.147 ERROR 17674 — [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Servlet execution threw an exception] with root cause

java.lang.ClassNotFoundException: com.exp.LoggingAdvice`

In the output, check

LOL

It is present in the same ClassFile(LoggingAdvice), but wherever there is a First class variable in the function, it throws ClassNotFoundException.

Can anyone Help ? I am a beginner at this bytecode manipulation and unfortunately, to classloading concept aswell.

[raphw]

For debugging, please consider to add AgentBuilder.Listener.StreamWriting.toSystemOut() in your build configuration. It will show you your agent’s activity.

Glad you figured it out.

[Blacias]

Bytebuddy is able to instrument java.sql.Statement without pushing the agent into the Bootstrap Loader. In my case what I wanted to check is, whenever a call is made from my java application to a mysql DB, I wanted my agent to trace it.

For that, I tried to instrument java.sql.Statement, but was facing some issues. So I added SystemOut listener and found out that Bytebuddy was not able to find my Advice class : java.lang.IllegalStateException: Cannot resolve type description for com.exp.innerloader.DBTracing

I am using an agentLoader which loads my main agent in a CustomClassLoader. So I added my advice files to the agentLoader, which in turn, loaded the advice class in SystemClassLoader and then, my agent was easily able to find the Advice class.