字节码编程javassist之打印方法耗时和入参

写在前面

本文看下如何实现打印方法耗时和入参。

1：程序

需要增强的类：

public class ApiTest1 {

    public Integer strToInt(String str01, String str02) {
        return Integer.parseInt(str01);
    }

}

插桩类

package com.dahuyou.javassist.huohuo.aa;

import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;

import java.lang.reflect.Method;

public class MyDoIt extends ClassLoader {
    public static void main(String[] args) throws Exception {
        ClassPool pool = ClassPool.getDefault();
        // 获取类和方法
        CtClass ctClass = pool.get(ApiTest1.class.getName());
        ctClass.replaceClassName("ApiTest1", "ApiTest12");
        String clazzName = ctClass.getName();
        CtMethod ctMethod = ctClass.getDeclaredMethod("strToInt");

        // 定义局部变量 注意必须声明，而不能直接在代码中写int xx = 222;这种，否则会报CannotCompileException: [source error] no such field: xxx
        ctMethod.addLocalVariable("startTime", CtClass.longType);
        ctMethod.addLocalVariable("incomingParameters", pool.get(Object[].class.getName()));

        // 方法前加强
//        ctMethod.insertBefore("{ startTime = System.nanoTime(); incomingParameters = new Object[]{$1, $2}; }");
        ctMethod.insertBefore("{ startTime = System.nanoTime(); incomingParameters = new Object[2]; incomingParameters[0] = $1; incomingParameters[1] = $2; }");

        // 方法后加强,输出耗时和参数
        ctMethod.insertAfter("System.out.println(\"执行耗时：\" + (System.nanoTime() - startTime));");


        // 测试调用
        byte[] bytes = ctClass.toBytecode();
        Class<?> clazzNew = new MyDoIt().defineClass("com.dahuyou.javassist.huohuo.aa.ApiTest1", bytes, 0, bytes.length);

        // 反射运行测试
        Class aClass = clazzNew;
        Object obj = aClass.newInstance();
        Method main = aClass.getDeclaredMethod("strToInt", String.class, String.class);
        main.invoke(obj, "99", "87");

//        System.out.println("执行耗时：" + (System.nanoTime() - startTime));
        ctClass.writeFile();


    }
}