如何使用java方法？ [英] How to instrument java methods?

问题描述

我想编写一个简单的java代理，它可以打印由java程序调用的方法的名称。

I want to write a simple java agent which can print the name of a method called by the java program instrumented.

例如，我想要测试的java程序是：

For example, my java program I want to instrument is:

public class TestInstr {

public static void sayHello() {
    System.out.println("Hello !");
}

public static void main(String args[]) {
    sayHello();
    sayHello();
    sayHello();
 }

}

我想显示像这个：

method sayHello has been called
Hello !
method sayHello has been called
Hello !
method sayHello has been called
Hello !

感谢您的帮助！

推荐答案

您可以使用Javassist之类的检测库来实现这一点。

You can use an instrumentation library such as Javassist to do that.

让我举一个单一方法的例子，你可以使用Javassist或反射将其扩展到所有方法：

Let me give you an example for a single method, you can extend this to all methods using Javassist or reflection:

ClassPool pool = ClassPool.getDefault();
CtClass cc = pool.get("TestInstr");
CtMethod m = cc.getDeclaredMethod("sayHello");
m.insertBefore("{ System.out.println(\"method sayHello has been called\"); }");
cc.writeFile();

查看此链接了解详情： http://www.csg.ci.iu-tokyo.ac.jp/~chiba/javassist/ tutorial / tutorial2.html #intro

Check this link for details: http://www.csg.ci.i.u-tokyo.ac.jp/~chiba/javassist/tutorial/tutorial2.html#intro

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