Append Agent to classpath

Question

I am trying to instrument Java ThreadPoolExecutor class using byte buddy. I am using my own logger to get logs from agent. But when i try to use this logger with Advice its gives following error.

Exception in thread "main" java.lang.NoClassDefFoundError: com/github/shehanperera/threadagent/GetLoggers
        at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.<clinit>(ThreadPoolExecutor.java)
        at java.util.concurrent.ThreadPoolExecutor.<clinit>(ThreadPoolExecutor.java:550)
        at java.util.concurrent.Executors.newFixedThreadPool(Executors.java:89)
        at com.github.shehanperera.threadpool.RunThreads.main(RunThreads.java:23)

using answer from Rafael Winterhalter for this Slf4j loggers with Byte Buddy , I used following code in agent to load my agent jar to the boot path.

JarFile jarFile = null;
        try {
            jarFile = new JarFile(new File("threadpool-agent-1.0-SNAPSHOT.jar"));

        } catch (IOException e) {
            e.printStackTrace();
        }
        instrumentation.appendToBootstrapClassLoaderSearch(jarFile);

But now i am getting following error

Exception in thread "main" java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:386)
        at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:401)
Caused by: java.lang.LinkageError: loader constraint violation: when resolving method "net.bytebuddy.agent.builder.AgentBuilder$Default.ignore(Lnet/bytebuddy/matcher/ElementMatcher;)Lnet/bytebuddy/agent/builder/AgentBuilder$Ignored;" the class loader (instance of sun/misc/Launcher$AppClassLoader) of the current class, com/github/shehanperera/threadagent/Agent, and the class loader (instance of <bootloader>) for the method's defining class, net/bytebuddy/agent/builder/AgentBuilder$Default, have different Class objects for the type net/bytebuddy/matcher/ElementMatcher used in the signature
        at com.github.shehanperera.threadagent.Agent.premain(Agent.java:33)
        ... 6 more

Any suggestion to solve this problem ?

Rafael Winterhalter Rafael Winterhalter · Accepted Answer · 2018-04-20T12:52:43

It seems as if you are adding the same class to multiple class loaders what can cause problems, especially if you add those classes lazily. Idealy, you use a build tool like the Shade plugin for Maven or the Shadow plugin for Gradle to bundle all of your classes into the jar file that represents the Java agent.

Append Agent to classpath

1 Answers