根据本教程，我尝试让java代理工作。https://www.baeldung.com/java-instrumentation#loading-a-java-agent

我确实得到了[Agent]转换类TestApplication我没有错误，但是我看不到转换类的任何效果。

最终我想让静态负载和动态负载都工作，但现在我专注于静态方式。

public class Static_Agent {

    public static void premain(String agentArgs, Instrumentation inst) {
        String[] tokens = agentArgs.split(";");
        String className = tokens[0];
        String methodName = tokens[1];

        System.out.println(">> "+className);
        System.out.println(">> "+methodName);
        transformClass(className, methodName, inst);
    }



    public static void transformClass(String className, String methodName, Instrumentation instrumentation) {
        Class<?> targetCls = null;
        ClassLoader targetClassLoader = null;
        // see if we can get the class using forName
        try {
            targetCls = Class.forName(className);
            targetClassLoader = targetCls.getClassLoader();
            transform(targetCls, methodName, targetClassLoader, instrumentation);
            return;
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        // otherwise iterate all loaded classes and find what we want
        for(Class<?> clazz: instrumentation.getAllLoadedClasses()) {
            if(clazz.getName().equals(className)) {
                targetCls = clazz;
                targetClassLoader = targetCls.getClassLoader();
                transform(targetCls, methodName, targetClassLoader, instrumentation);
                return;
            }
        }
        throw new RuntimeException("Failed to find class [" + className + "]");
    }


    public static void transform(Class<?> clazz, String methodName, ClassLoader classLoader, Instrumentation instrumentation) {
        Transformer dt = new Transformer(clazz.getName(), methodName, classLoader);
        instrumentation.addTransformer(dt, true);
        try {
            instrumentation.retransformClasses(clazz);
        } catch (Exception ex) {
            throw new RuntimeException("Transform failed for class: [" + clazz.getName() + "]", ex);
        }
    }



}

public class Transformer implements ClassFileTransformer {


    /** The internal form class name of the class to transform */
    private String targetClassName;
    /** The class loader of the class we want to transform */
    private ClassLoader targetClassLoader;

    private String targetMethodName;

    public Transformer(String targetClassName, String targetMethodName, ClassLoader targetClassLoader) {
        this.targetClassName = targetClassName;
        this.targetClassLoader = targetClassLoader;
        this.targetMethodName = targetMethodName;
    }

    @Override
    public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
            ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
        byte[] byteCode = classfileBuffer;

        String finalTargetClassName = this.targetClassName.replaceAll("\\.", "/");
        if (!className.equals(finalTargetClassName)) {
            return byteCode;
        }

        if (className.equals(finalTargetClassName) && loader.equals(targetClassLoader)) {
            System.out.println("[Agent] Transforming class TestApplication");
            try {

                ClassPool cp = ClassPool.getDefault();
                CtClass cc = cp.get(targetClassName);
                CtMethod m = cc.getDeclaredMethod(targetMethodName);
                m.addLocalVariable("startTime", CtClass.longType);
                m.insertBefore("startTime = System.currentTimeMillis();");

                StringBuilder endBlock = new StringBuilder();

                m.addLocalVariable("endTime", CtClass.longType);
                m.addLocalVariable("opTime", CtClass.longType);
                endBlock.append("endTime = System.currentTimeMillis();");
                endBlock.append("opTime = (endTime-startTime)/1000;");

                endBlock.append("System.out.println(\"[Application] Withdrawal operation completed in:\" + opTime + \" seconds!\");");

                m.insertAfter(endBlock.toString());

                byteCode = cc.toBytecode();
                cc.detach();
            } catch (Exception e) {
                System.out.println("Exception"+e);
            }
        }
        return byteCode;
    }
}

public class TestApplication {

    public static void main(String[] args) {

        try {
            TestApplication.run();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    public static void run() throws Exception {
        System.out.println("--- start ---");

        while (true) {
            test();
            Thread.sleep(4_000);
        }


    }


    static int count = 0;

    public static void test() {
        System.out.println(count++);
    }

}

我启动：

java-javaagent：static_agent. jar="doeke.application.TestApplication；test"-jarapplication.jar

如果有帮助，项目在这里：https://github.com/clankill3r/java_agent

编辑：

在文件末尾的Transformer.java中，我现在使用e. printStackTrace（）；。

我收到以下错误：

---启动---

0

1