javassist是否允许在条件表达式中修改运算符? [英] Does javassist let modify an operator in a conditional expression?

问题描述

我需要知道是否可以使用以下代码和javassist来操纵代码，以将逻辑运算符>"替换为<".

这是我要操作其字节码的类:

 公共类TryClass {公共无效foo(){int a = 0;如果(a> 5){System.out.println(我爱苹果");}别的{System.out.println(我讨厌苹果");}}} 

在操作之后，该类的执行应打印:我爱苹果"代替:我讨厌苹果"

解决方案

在字节码级别本身没有< 或> ，它是<例如，使用code> if_icmple 进行比较-这是一条实际的字节码指令.像这样的 javassist 应该能够做到这一点，它被称为 build-time字节码检测工具，网上有很多关于此的文章." with "<".

Here is the class whose bytecode I want to manipulate:

public class TryClass {
    public void foo(){
        int a =0;
        if(a>5){
            System.out.println("I love apples");
       }
        else{
            System.out.println("I hate apples");
       }
    }
}

After the manipulation the execution of the class should print: "I love apples" instead of: "I hate apples"

解决方案

there is no < or > at the byte code level per-se, it's if_icmple for example used for comparison - meaning it's an actual byte code instruction. As such javassist should be able to do it, it's called build-time byte-code instrumentation and there are quite a few article online about this. Here is one for example

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