015-JVM-使用javap查看class文件内容

2021年10月18日 172次阅读 来源: 前路无畏

上一篇：014-JVM-查看class文按键的工具Binary viewer、ue、classlib Bytecode viewer https://blog.csdn.net/fsjwin/article/details/111423443
处理使用上面的工具还可以使用javap查看class文件的格式

1. 使用javap -v 查看Helloworld.class文件

Microsoft Windows [版本 10.0.19041.685]
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D:\MCA\JVM\out\production\JVM\com\yuhl>javap -v Helloword.class
Classfile /D:/MCA/JVM/out/production/JVM/com/yuhl/Helloword.class
  Last modified 2020-12-19; size 547 bytes
  MD5 checksum 0d5b91ddd1f20c608a7cabc0eb01efec
  Compiled from "Helloword.java"
public class com.yuhl.Helloword
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref #6.#20 // java/lang/Object."<init>":()V
   #2 = Fieldref #21.#22 // java/lang/System.out:Ljava/io/PrintStream;
   #3 = String #23 // Helloword!
   #4 = Methodref #24.#25 // java/io/PrintStream.println:(Ljava/lang/String;)V
   #5 = Class #26 // com/yuhl/Helloword
   #6 = Class #27 // java/lang/Object
   #7 = Utf8 <init>
   #8 = Utf8 ()V
   #9 = Utf8 Code
  #10 = Utf8 LineNumberTable
  #11 = Utf8 LocalVariableTable
  #12 = Utf8 this
  #13 = Utf8 Lcom/yuhl/Helloword;
  #14 = Utf8 main
  #15 = Utf8 ([Ljava/lang/String;)V
  #16 = Utf8 args
  #17 = Utf8 [Ljava/lang/String;
  #18 = Utf8 SourceFile
  #19 = Utf8 Helloword.java
  #20 = NameAndType #7:#8 // "<init>":()V
  #21 = Class #28 // java/lang/System
  #22 = NameAndType #29:#30 // out:Ljava/io/PrintStream;
  #23 = Utf8 Helloword!
  #24 = Class #31 // java/io/PrintStream
  #25 = NameAndType #32:#33 // println:(Ljava/lang/String;)V
  #26 = Utf8 com/yuhl/Helloword
  #27 = Utf8 java/lang/Object
  #28 = Utf8 java/lang/System
  #29 = Utf8 out
  #30 = Utf8 Ljava/io/PrintStream;
  #31 = Utf8 java/io/PrintStream
  #32 = Utf8 println
  #33 = Utf8 (Ljava/lang/String;)V
{ 
  public com.yuhl.Helloword();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1 // Method java/lang/Object."<init>":()V
         4: return
      LineNumberTable:
        line 9: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Lcom/yuhl/Helloword;

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=2, locals=1, args_size=1
         0: getstatic     #2 // Field java/lang/System.out:Ljava/io/PrintStream;
         3: ldc           #3 // String Helloword!
         5: invokevirtual #4 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
         8: return
      LineNumberTable:
        line 11: 0
        line 12: 8
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       9     0  args   [Ljava/lang/String;
}
SourceFile: "Helloword.java"

D:\MCA\JVM\out\production\JVM\com\yuhl>

简单说明：

  1. Classfile：类文件
  2. Constant pool:常量池
  3. SourceFile:源文件

因为这java类写的比较简单，所以很多信息是没有的，但是遇到问题就参考前面的字典就可以解读了
014-JVM-Class文件结构概况https://blog.csdn.net/fsjwin/article/details/111422262

2. 把javap 集成到idea工具中

2.1效果

《015-JVM-使用javap查看class文件内容》
external tools添加很简单，自行解决之：
《015-JVM-使用javap查看class文件内容》
看到的效果和使用命令一样的
《015-JVM-使用javap查看class文件内容》
下一篇：016-JVM-十六进制class文件简单解读 https://blog.csdn.net/fsjwin/article/details/111462867

    原文作者：前路无畏
    原文地址: https://blog.csdn.net/fsjwin/article/details/111426985
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