javassist簡介

Javassist是一個開源的分析、編輯和創(chuàng)建Java字節(jié)碼的類庫。

demo目的給一個字節(jié)碼里面的構(gòu)造方法添加一個輸出語句

• 待添加的java類

package com.suse.yuxin;
public class User {
    private String userName;
    private String userNumber;
    
    public User(String userName, String userNumber) {
        super();
        this.userName = userName;
        this.userNumber = userNumber;
    }
    
  }

• 測試代碼

public class TestAssist {
    public static void main(String args[]) throws NotFoundException, CannotCompileException, IOException{
        ClassPool pool = ClassPool.getDefault();
        //設(shè)置classPath
        pool.appendClassPath("D:\\javaworkspace\\Test\\bin");
        //獲取一個class文件
        CtClass ctClass = pool.get("com.suse.yuxin.User");
        //獲取構(gòu)造方法
        CtConstructor ctConstructor = ctClass.getConstructors()[0];
        //插入輸出語句
        ctConstructor.insertAfter("System.out.println();");
        ctClass.writeFile("D:\\javaworkspace\\Test\\bin\\output");
        System.out.println("OK");
    }
    
    }

• 反編譯查看

  
  

工具

• javassist jar 包使用的是3.9.0
• 反編譯使用的工具是 jd-gui

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