transform not working when attaching agentmain dynamically

[qujsh]

Hey, I had a simple static agent that I attached with -javaagent and everything worked fine. Now I tried changing it to work dyamically in agentmain, it worked without println in transform, I don't no why.

I had a check in issue similarly, ref: #1164. But It didn't solve my problem. Here's my code:

public static void agentmain(String agentArgs, Instrumentation inst) {

        System.out.println("Agentmain initialized.");

        new AgentBuilder.Default()
                .disableClassFormatChanges()
                .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
//                .type(ElementMatchers.any())   //it's also ineffective；
                .type(ElementMatchers.nameContains("example"))
                .transform((builder, type, classLoader, module, protectionDomain) -> {

                    System.out.println("className: " + type.getName());

                    Advice advice = Advice.to(TimingAdvice.class);
                    return builder.visit(advice.on(ElementMatchers.any()));
                })
                .installOn(inst);

        System.out.println("Agent initialized successfully!");
    }

I can see the "Agentmain initialized." and "Agent initialized successfully!" print when I attach the agent so I know it's being attached, but the transform is never called with no "className: xxx" print.

bytebuddy: 1.15.11
java: 1.8.0

[qujsh]

my goal is to print the execution time for each method execution. now I execute the spring HealthController.health() by curl, I can get response but no execution time print.

[qujsh]

TimingAdvice code

public class TimingAdvice {

    @Advice.OnMethodEnter
    public static long onEnter(@Advice.Origin String method) {
//        System.out.println("Entering method: " + method);
        return System.nanoTime();
    }

    @Advice.OnMethodExit
    public static void onExit(@Advice.Origin String method,
                              @Advice.Enter long startTime) {
        long duration = System.nanoTime() - startTime;
        System.out.println("Exiting method: " + method + " took " + duration + "ns");
    }
}

main code

    public static void main(String[] args) throws IOException, AttachNotSupportedException, AgentLoadException, AgentInitializationException {

        String jarStartupPath = System.getProperty("user.dir");
        System.out.println("JAR startup path: " + jarStartupPath);
        for (VirtualMachineDescriptor vmd : VirtualMachine.list()) {

            if (vmd.displayName().startsWith("example")) {
                System.out.println("Found JVM: " + vmd.displayName() + " [" + vmd.id() + "]");

                VirtualMachine vm = VirtualMachine.attach(vmd.id());
                vm.loadAgent("/src/main/resources/gatherv2-1.0-SNAPSHOT.jar");
                vm.detach();
                System.out.println("Agent attached to JVM with ID: " + vmd.id());
                break;
            }
        }
    }

pom.xml

  <dependencies>

        <dependency>
            <groupId>net.bytebuddy</groupId>
            <artifactId>byte-buddy</artifactId>
            <version>1.15.11</version> <!-- 请检查 Byte Buddy 的最新版本 -->
        </dependency>

        <dependency>
            <groupId>net.bytebuddy</groupId>
            <artifactId>byte-buddy-agent</artifactId>
            <version>1.15.11</version> <!-- 请检查 Byte Buddy 的最新版本 -->
        </dependency>

        <dependency>
            <groupId>com.sun</groupId>
            <artifactId>tools</artifactId>
            <version>1.8.0</version>  <!-- 需要根据你的 JDK 版本选择合适的版本 -->
            <scope>system</scope>
            <!-- 需要正确配置环境变量 JAVA_HOME的值，常规 java -version使用的是jre环境，tools.jar在Java 8中落在jdk环境中 -->
            <systemPath>${java.home}/../lib/tools.jar</systemPath>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.6.0</version> <!-- 使用最新版本 -->
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <createDependencyReducedPom>false</createDependencyReducedPom>
                            <filters>
                                <filter>
                                    <artifact>*:*</artifact>
                                    <excludes>
                                    </excludes>
                                </filter>
                            </filters>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.4.2</version>
                <configuration>
                    <archive>
                        <manifestEntries>
                            <Premain-Class>org.example.ByteBuddyAdvice</Premain-Class>
                            <Main-Class>org.example.Main</Main-Class>

                            <Agent-Class>org.example.ByteBuddyAdvice</Agent-Class>
                            <Can-Retransform-Classes>true</Can-Retransform-Classes>
                            <Can-Redefine-Classes>true</Can-Redefine-Classes>
                        </manifestEntries>
                    </archive>
                </configuration>
            </plugin>
        </plugins>
    </build>

[raphw]

Could you register an Agent builder.Listener to see if the classes you wonder about are picked up?

[qujsh]

I add the builder.Listener and can print typeName, even when I execute curl to HealthController.health() is also do print, but transform do nothing, no className print. Here's my code and result:

public static void agentmain(String agentArgs, Instrumentation inst) {

        System.out.println("Agentmain initialized.");

        // add Agent Listener
        ByteBuddyListener listener = new ByteBuddyListener();

        new AgentBuilder.Default()
                .disableClassFormatChanges()
                .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
//                .type(ElementMatchers.any()) 
                .type(ElementMatchers.nameContains("HealthController"))  //only use HealthController to test
                .transform((builder, type, classLoader, module, protectionDomain) -> {

                    System.out.println("className: " + type.getName()); //no className print

                    Advice advice = Advice.to(TimingAdvice.class);
                    return builder.visit(advice.on(ElementMatchers.any()));
                })
                .with(listener)  //add Agent Listener here
                .installOn(inst);

        System.out.println("Agent initialized successfully!");
}

ByteBuddyListener:

public class ByteBuddyListener implements AgentBuilder.Listener {
    @Override
    public void onDiscovery(String typeName, ClassLoader classLoader, JavaModule javaModule, boolean b) {
        System.out.println("Discovered: " + typeName);
    }

    @Override
    public void onTransformation(TypeDescription typeDescription, ClassLoader classLoader, JavaModule javaModule, boolean b, DynamicType dynamicType) {
        System.out.println("Transformed: " + typeDescription.getName());
    }

    @Override
    public void onIgnored(TypeDescription typeDescription, ClassLoader classLoader, JavaModule javaModule, boolean b) {
        System.out.println("Ignored: " + typeDescription.getName());
    }

    @Override
    public void onError(String typeName, ClassLoader classLoader, JavaModule javaModule, boolean b, Throwable throwable) {
        System.out.println("Error: " + typeName);
    }

    @Override
    public void onComplete(String typeName, ClassLoader classLoader, JavaModule javaModule, boolean b) {
        System.out.println("Complete: " + typeName);
    }
}

result:

[raphw]

I see an error in the log. What does the exception say?

[qujsh]

Thank you for your reply. I will go to the company on Monday to test what the printing error is. At that time, the project can only be debugged in the local network. Inspired by you, I started a very simple Spring project, and its Spring HealthController has been successfully adjusted.

[qujsh]

I found the issue. It's because the spring-test plugin I depend on introduces mockio, which relies on an older version 1.10. The latest version 1.15 that I'm using throws an error when using agentmain, with the following error message. So, to ensure compatibility across multiple projects and versions, I can only use the -javaagent mode, right? It works fine when using that.

[raphw]

Can't you use dependency configuration to pin the latest version?

[qujsh]

It seems like I can't handle it this way. It's a dependency of a dependency of a dependency.

[raphw]

If you use Maven, for example, you'd use dependency configuration.

[qujsh]

Thank you for your reply, I will check it again.