I want to register my custom class or a 3rd-party class(or lib) with the class loader.

[JangCool]

I was told to use the isHelperClass method in the InstrumentationModule, but it doesn't seem to be working.

  @Override
  public boolean isHelperClass(String className) {
    return className.startsWith("kr.co.pionnet.hamonica2.agent.cache");
  }

I want to call my custom class at the start or end of a method. However, due to a class loader issue, a NoClassDefFoundError error occurs.

java.lang.NoClassDefFoundError: kr/co/pionnet/hamonica2/extension/ControllerInstrumentation
	at kr.co.pionnet.hamonica2.ha.system.controllers.CodesController.getCodes(CodesController.java:24)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:255)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:188)
	at ...

package kr.co.pionnet.hamonica2.extension;

import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;

import static net.bytebuddy.matcher.ElementMatchers.*;

import kr.co.pionnet.hamonica2.agent.cache.HamonicaCacheExecutor;
import net.bytebuddy.asm.Advice;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.matcher.ElementMatcher;

public class ControllerInstrumentation implements TypeInstrumentation {

    public static final String CLASS_NAME = "kr.co.pionnet.hamonica2.ha.system.controllers.CodesController";

    public static final HamonicaCacheExecutor hamonicaCacheExecutor = new HamonicaCacheExecutor();

    @Override
    public ElementMatcher<TypeDescription> typeMatcher() {

        System.out.println(" call typeMatcher" + named(CLASS_NAME));
        return named(CLASS_NAME);

    }

    @Override
    public void transform(TypeTransformer typeTransformer) {

        System.out.println(" call transform");

        typeTransformer.applyAdviceToMethod(
               isMethod().and(isPublic()),
            this.getClass().getName() + "$ControllerAdvice"
        );

    }

    @SuppressWarnings("unused")
    public static class ControllerAdvice {

        @Advice.OnMethodEnter(suppress = Throwable.class)
        public static void onEnter() {
            System.out.println("controller enter");
            hamonicaCacheExecutor.getValue("abcd ", null);
        }

        @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
        public static void onExit(@Advice.Thrown Throwable throwable) {
            System.out.println("controller exit");
            hamonicaCacheExecutor.putValue("ss",null, null);
        }
    }
}

build.gradle

 -----------------------------------------------------------------------------------------------------------*/
plugins {

    id "io.opentelemetry.instrumentation.muzzle-generation" version "2.6.0-alpha"
    id "io.opentelemetry.instrumentation.muzzle-check" version "2.6.0-alpha"
}



apply plugin: 'io.opentelemetry.instrumentation.muzzle-generation'
apply plugin: 'io.opentelemetry.instrumentation.muzzle-check'
apply from: 'dependency.gradle'


muzzle {
}

dependency.gradle

compileJava {
    options.annotationProcessorPath = configurations.annotationProcessor
}


dependencies {

    implementation 'io.opentelemetry.instrumentation:opentelemetry-instrumentation-api:2.6.0'
//    implementation 'io.opentelemetry.instrumentation:opentelemetry-instrumentation-api-annotation-support:2.6.0-alpha'

    implementation 'io.opentelemetry.javaagent:opentelemetry-javaagent-extension-api:2.6.0-alpha'

    // https://mvnrepository.com/artifact/com.google.auto.service/auto-service
    implementation "com.google.auto.service:auto-service:1.1.1"
    annotationProcessor 'com.google.auto.service:auto-service:1.1.1'

}

Do I need to use a library called Muzzle? There isn't enough information in the manual to follow along, making it difficult to set up. Can you provide detailed instructions?

[laurit]

The error message says java.lang.NoClassDefFoundError: kr/co/pionnet/hamonica2/extension/ControllerInstrumentation With your isHelperClass implementation you inject classes in kr.co.pionnet.hamonica2.agent.cache but ControllerInstrumentation is in a different package. Usually the solution is to make sure that inside your advice class you don't use the type instrumentation class that contains the advice. Instead of having the hamonicaCacheExecutor field on the instrumentation class move it to a different class that is in a package that is injected.

[JangCool]

ok.. but..

 @SuppressWarnings("unused")
    public static class ControllerAdvice {

        @Advice.OnMethodEnter(suppress = Throwable.class)
        public static void onEnter() {
            System.out.println("controller enter");
            HamonicaCacheExecutor.getValue("abcd ", null);
        }

        @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
        public static void onExit(@Advice.Thrown Throwable throwable) {
            System.out.println("controller exit");
            HamonicaCacheExecutor.putValue("ss",null, null);
        }
    }

  @Override
  public List<String> getAdditionalHelperClassNames() {
    return List.of("kr.co.pionnet.hamonica2.agent.cache.HamonicaCacheExecutor");
  }

It seems like the isHelperClass method is not working properly. When I manually specify full class paths using the getAdditionalHelperClassNames method, it works fine.

However, if there are many user-defined classes, it becomes burdensome to list each one individually.

Could you please provide the correct usage for making the isHelperClass method work? Does the advice class need to be placed in the same package path as the helper class?

[laurit]

Automatic discovery of helper classes is handled by muzzle generation plugin. See the example extension https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/examples/extension/build.gradle for how it is configured. If you are unable to make it work then pleas provide a minimal sample that reproduces the issue.

[JangCool]

asking and answering oneself:

build.gradle:

plugins {

    id "io.opentelemetry.instrumentation.muzzle-generation" version "2.6.0-alpha"
    id "io.opentelemetry.instrumentation.muzzle-check" version "2.6.0-alpha"
}

dependency.gradle:

dependencies {
    runtimeOnly 'io.opentelemetry.javaagent:opentelemetry-muzzle:2.6.0-alpha'
}

The JAR task runs, and the isHelperClass function is called. I confirmed that the isHelperClass function is called during the compile and build stages