使用byte buddy的Advice时，抛出Exception of java.lang.NoClassDefFoundError

Question

出于某种原因，我一直在分析我自己的旧 jar 文件（不幸的是源代码丢失了）。我知道我要找到哪个部分，但不记得它在哪里。所以决定使用byte buddy来获取jar文件的所有运行流。记录所有 classes 中所有方法的参数值和 return 值就足够了（库 class 除外，例如 java.lang.*）。我尝试了稍作修改的示例代码，但只出现了一个例外：

 public static void premain(final String agentArgs,
                           final Instrumentation inst) {
    System.out.println(
            "+++Hey, look: I'm instrumenting a freshly started JVM!");
    new AgentBuilder.Default()
            .type(ElementMatchers.any())
            .transform(new MetricsTransformer())
            .with(AgentBuilder.Listener.StreamWriting.toSystemOut())
            .with(AgentBuilder.TypeStrategy.Default.REDEFINE)
            .installOn(inst);
}

private static class MetricsTransformer implements AgentBuilder.Transformer {
    @Override
    public DynamicType.Builder<?> transform(
            final DynamicType.Builder<?> builder,
            final TypeDescription typeDescription,
            final ClassLoader classLoader,
            final JavaModule module) {

        final AsmVisitorWrapper methodsVisitor =
                Advice.to(EnterAdvice.class, ExitAdviceMethods.class)
                        .on(ElementMatchers.isAnnotatedWith(CollectMetrics.class)
                                .and(ElementMatchers.isMethod()));

        final AsmVisitorWrapper constructorsVisitor =
                Advice.to(EnterAdvice.class, ExitAdviceConstructors.class)
                        .on(ElementMatchers.isAnnotatedWith(CollectMetrics.class)
                                .and(ElementMatchers.isConstructor()));

        return builder.visit(methodsVisitor).visit(constructorsVisitor);
    }

    private static class EnterAdvice {
        @Advice.OnMethodEnter
        static long enter() {
            return System.nanoTime();
        }
    }

    private static class ExitAdviceMethods {
        @Advice.OnMethodExit(onThrowable = Throwable.class)
        static void exit(@Advice.Origin final Executable executable,
                         @Advice.Enter final long startTime,
                         @Advice.Thrown final Throwable throwable) {
            final long duration = System.nanoTime() - startTime;
            System.out.println(duration);;
        }
    }

}

字节哥的版本是1.9.5,1.7.11 jdk版本：1.8.0.191

和 cmd 中的异常：

    E:\>cd E:\workshop\_android_studio\BounAgent\out\artifacts\BounAgent_jar

E:\BounAgent_jar>java -javaagent:BounAgent.jar -jar untitled.jar
Exception in thread "main" java.lang.NoClassDefFoundError: net/bytebuddy/matcher
/ElementMatcher
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
        at java.lang.Class.getDeclaredMethod(Unknown Source)
        at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(Unknown Sou
rce)
        at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(Unknown So
urce)
Caused by: java.lang.ClassNotFoundException: net.bytebuddy.matcher.ElementMatche
r
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 5 more

本机方法中的致命错误：-javaagent 处理失败

提前致谢。

Answer 1

根据an article我发现：

To launch your agent you must bundle the agent classes and resources in a jar, and in the jar manifest set the Agent-Class property to the name of your agent class containing the premain method. (An agent must always be bundled as a jar file, it cannot be specified in an exploded format.)

您的代理 JAR 文件 ("BounAgent.jar") 似乎未包含正确形式的所有依赖项。具体来说，bytebuddy 类不在 JAR 文件中。这导致代理类无法加载。

使用byte buddy的Advice时，抛出Exception of java.lang.NoClassDefFoundError

When using Advice of byte buddy, Exception of java.lang.NoClassDefFoundError is throwed

java

javaagents

byte-buddy