javap 以一种可编程的方式 [英] javap in a programmable way

问题描述

我们可以在我们自己的java代码中以可编程的方式使用javap吗?

Can we use javap in our own java code in a programmable way?

例如以下代码:

public class TestClass {
    public static void main(String[] args) {
        System.out.println("hello world");
    }
}

在命令行中使用 javap，我们得到:

using javap in command line, we got :

// Header + consts 1..22 snipped
const #22 = String      #23;    //  hello world
const #23 = Asciz       hello world;

public static void main(java.lang.String[]);
  Signature: ([Ljava/lang/String;)V
  Code:
   Stack=2, Locals=1, Args_size=1
   0:   getstatic       #16; //Field java/lang/System.out:Ljava/io/PrintStream;
   3:   ldc     #22; //String hello world
   5:   invokevirtual   #24; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
   8:   return
  // Debug info snipped
}

我可以使用 javap 的 API 只打印常量池吗?

can I print only the Constant Pool using javap's API?

推荐答案

Apache BCEL 提供封装.class 文件解析，提供了一套 API.几乎对于 .class 文件中的每个元素，BECL API 中都有一个对应的 Class 来表示它.因此，在某种程度上，如果您只想打印出类文件的某些部分，就不是那么简单了.这里有一个简单的例子你可以参考，注意org.apache.bcel.classfile.ClassParser:

Apache BCEL provides encapsulations of .class file parsing, which provides a set of API. Almost for every element in .class file, there's a corresponding Class in BECL API to represent it. So in some way, it is not that straightforward if you just want to print out certain sections of the class file. Here is a simple example you can refer, pay attention to the org.apache.bcel.classfile.ClassParser:

    ClassParser cp = new ClassParser("TestClass.class");
    JavaClass jc = cp.parse();
    ConstantPool constantPool = jc.getConstantPool(); // Get the constant pool here.
    for (Constant c : constantPool.getConstantPool()) {
        System.out.println(c); // Do what you need to do with all the constants.
    }

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