015-JVM-使用javap查看class文件内容

「爱情、让人受尽委屈。」 2022-12-29 04:54 180阅读 0赞

[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][014-JVM-_class_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]
    (c) 2020 Microsoft Corporation. 保留所有权利。
    
    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][014-JVM-Class_https_blog.csdn.net_fsjwin_article_details_111422262]

# 2. 把javap 集成到idea工具中 #

## 2.1效果 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Zzandpbg_size_16_color_FFFFFF_t_70]  
external tools添加很简单，自行解决之：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Zzandpbg_size_16_color_FFFFFF_t_70 1]  
看到的效果和使用命令一样的  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Zzandpbg_size_16_color_FFFFFF_t_70 2]  
[下一篇：016-JVM-十六进制class文件简单解读 https://blog.csdn.net/fsjwin/article/details/111462867][016-JVM-_class_ https_blog.csdn.net_fsjwin_article_details_111462867]

[014-JVM-_class_Binary viewer_ue_classlib Bytecode viewer https_blog.csdn.net_fsjwin_article_details_111423443]: https://blog.csdn.net/fsjwin/article/details/111423443
[014-JVM-Class_https_blog.csdn.net_fsjwin_article_details_111422262]: https://blog.csdn.net/fsjwin/article/details/111422262
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Zzandpbg_size_16_color_FFFFFF_t_70]: /images/20221120/685c24679f404656b7400cd3afa949f1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Zzandpbg_size_16_color_FFFFFF_t_70 1]: /images/20221120/15ac5726f98947d68b190198812aac4a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Zzandpbg_size_16_color_FFFFFF_t_70 2]: /images/20221120/872b9f81e04c4bc692bf527df76d4879.png
[016-JVM-_class_ https_blog.csdn.net_fsjwin_article_details_111462867]: https://blog.csdn.net/fsjwin/article/details/111462867