Class文件解析示例
java文件编译为class字节码文件后，示例如下：
Classfile /target/classes/com/jvm/bookdemo/z6/ClassCompileTest.class
Last modified May 17, 2019; size 1969 bytes
MD5 checksum 10ce34e6f69adca226d421a8ae082da0
Compiled from "ClassCompileTest.java"
public class com.jvm.bookdemo.z6.ClassCompileTest
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #25.#66 // java/lang/Object."":()V
#2 = Class #67 // java/lang/Long
#3 = Long 9223372036854775807l
#5 = Methodref #2.#68 // java/lang/Long.valueOf:(J)Ljava/lang/Long;
#6 = Fieldref #69.#70 // java/lang/System.out:Ljava/io/PrintStream;
#7 = Methodref #71.#72 // java/io/PrintStream.println:(Ljava/lang/Object;)V
#8 = Methodref #71.#73 // java/io/PrintStream.println:(I)V
#9 = Class #74 // java/util/ArrayList
#10 = Methodref #9.#66 // java/util/ArrayList."":()V
#11 = Class #75 // com/jvm/bookdemo/z6/ClassCompileTest
#12 = Methodref #11.#66 // com/jvm/bookdemo/z6/ClassCompileTest."":()V
#13 = InterfaceMethodref #76.#77 // java/util/List.add:(Ljava/lang/Object;)Z
#14 = Class #78 // java/lang/StringBuffer
#15 = Methodref #14.#79 // java/lang/StringBuffer."":(Ljava/lang/String;)V
#16 = Methodref #14.#80 // java/lang/StringBuffer.append:(Ljava/lang/String;)Ljava/lang/StringBuffer;
#17 = Methodref #14.#81 // java/lang/StringBuffer.toString:()Ljava/lang/String;
#18 = String #82 // 4E
#19 = Methodref #83.#84 // java/lang/Integer.parseInt:(Ljava/lang/String;I)I
#20 = Methodref #83.#85 // java/lang/Integer.toHexString:(I)Ljava/lang/String;
#21 = Methodref #71.#86 // java/io/PrintStream.println:(Ljava/lang/String;)V
#22 = String #87 // 222
#23 = Fieldref #11.#88 // com/jvm/bookdemo/z6/ClassCompileTest.CONSTANT_PARAM:Ljava/lang/String;
#24 = Fieldref #11.#89 // com/jvm/bookdemo/z6/ClassCompileTest.INT_PARAM:I
#25 = Class #90 // java/lang/Object
#26 = Utf8 FINAL_CONSTANT_PARAM
#27 = Utf8 Ljava/lang/String;
#28 = Utf8 ConstantValue
#29 = String #91 // 111
#30 = Utf8 CONSTANT_PARAM
#31 = Utf8 INT_PARAM
#32 = Utf8 I
#33 = Utf8
#34 = Utf8 ()V
#35 = Utf8 Code
#36 = Utf8 LineNumberTable
#37 = Utf8 LocalVariableTable
#38 = Utf8 this
#39 = Utf8 Lcom/jvm/bookdemo/z6/ClassCompileTest;
#40 = Utf8 appendStr
#41 = Utf8 (Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
#42 = Utf8 paraStr
#43 = Utf8 prefix
#44 = Utf8 g
#45 = Utf8 Ljava/lang/Long;
#46 = Utf8 a
#47 = Utf8 b
#48 = Utf8 c
#49 = Utf8 d
#50 = Utf8 e
#51 = Utf8 f
#52 = Utf8 list
#53 = Utf8 Ljava/util/List;
#54 = Utf8 ct
#55 = Utf8 sb
#56 = Utf8 Ljava/lang/StringBuffer;
#57 = Utf8 LocalVariableTypeTable
#58 = Utf8 Ljava/util/List;
#59 = Utf8 main
#60 = Utf8 ([Ljava/lang/String;)V
#61 = Utf8 args
#62 = Utf8 [Ljava/lang/String;
#63 = Utf8
#64 = Utf8 SourceFile
#65 = Utf8 ClassCompileTest.java
#66 = NameAndType #33:#34 // "":()V
#67 = Utf8 java/lang/Long
#68 = NameAndType #92:#93 // valueOf:(J)Ljava/lang/Long;
#69 = Class #94 // java/lang/System
#70 = NameAndType #95:#96 // out:Ljava/io/PrintStream;
#71 = Class #97 // java/io/PrintStream
#72 = NameAndType #98:#99 // println:(Ljava/lang/Object;)V
#73 = NameAndType #98:#100 // println:(I)V
#74 = Utf8 java/util/ArrayList
#75 = Utf8 com/jvm/bookdemo/z6/ClassCompileTest
#76 = Class #101 // java/util/List
#77 = NameAndType #102:#103 // add:(Ljava/lang/Object;)Z
#78 = Utf8 java/lang/StringBuffer
#79 = NameAndType #33:#104 // "":(Ljava/lang/String;)V
#80 = NameAndType #105:#106 // append:(Ljava/lang/String;)Ljava/lang/StringBuffer;
#81 = NameAndType #107:#108 // toString:()Ljava/lang/String;
#82 = Utf8 4E
#83 = Class #109 // java/lang/Integer
#84 = NameAndType #110:#111 // parseInt:(Ljava/lang/String;I)I
#85 = NameAndType #112:#113 // toHexString:(I)Ljava/lang/String;
#86 = NameAndType #98:#104 // println:(Ljava/lang/String;)V
#87 = Utf8 222
#88 = NameAndType #30:#27 // CONSTANT_PARAM:Ljava/lang/String;
#89 = NameAndType #31:#32 // INT_PARAM:I
#90 = Utf8 java/lang/Object
#91 = Utf8 111
#92 = Utf8 valueOf
#93 = Utf8 (J)Ljava/lang/Long;
#94 = Utf8 java/lang/System
#95 = Utf8 out
#96 = Utf8 Ljava/io/PrintStream;
#97 = Utf8 java/io/PrintStream
#98 = Utf8 println
#99 = Utf8 (Ljava/lang/Object;)V
#100 = Utf8 (I)V
#101 = Utf8 java/util/List
#102 = Utf8 add
#103 = Utf8 (Ljava/lang/Object;)Z
#104 = Utf8 (Ljava/lang/String;)V
#105 = Utf8 append
#106 = Utf8 (Ljava/lang/String;)Ljava/lang/StringBuffer;
#107 = Utf8 toString
#108 = Utf8 ()Ljava/lang/String;
#109 = Utf8 java/lang/Integer
#110 = Utf8 parseInt
#111 = Utf8 (Ljava/lang/String;I)I
#112 = Utf8 toHexString
#113 = Utf8 (I)Ljava/lang/String;
{
public static final java.lang.String FINAL_CONSTANT_PARAM;
descriptor: Ljava/lang/String;
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
ConstantValue: String 111
public static java.lang.String CONSTANT_PARAM;
descriptor: Ljava/lang/String;
flags: ACC_PUBLIC, ACC_STATIC
public static int INT_PARAM;
descriptor: I
flags: ACC_PUBLIC, ACC_STATIC
public com.jvm.bookdemo.z6.ClassCompileTest();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."":()V
4: return
LineNumberTable:
line 13: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this Lcom/jvm/bookdemo/z6/ClassCompileTest;
public java.lang.String appendStr(java.lang.String, java.lang.String);
descriptor: (Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
flags: ACC_PUBLIC
Code:
stack=3, locals=13, args_size=3
0: ldc2_w #3 // long 9223372036854775807l //ldc2_w 指令的含义是把long类型常量值从常量池中推送至栈顶
3: invokestatic #5 // Method java/lang/Long.valueOf:(J)Ljava/lang/Long;
6: astore_3
7: getstatic #6 // Field java/lang/System.out:Ljava/io/PrintStream;
10: aload_3
11: invokevirtual #7 // Method java/io/PrintStream.println:(Ljava/lang/Object;)V
14: iconst_1
15: istore 4
17: bipush 12
19: istore 5
21: iconst_3
22: istore 6
24: iconst_4
25: istore 7
27: bipush 6
29: istore 8
31: iload 4
33: iload 5
35: iconst_3
36: imul
37: iadd
38: iload 6
40: iadd
41: iload 7
43: iadd
44: iload 8
46: iadd
47: istore 9
49: getstatic #6 // Field java/lang/System.out:Ljava/io/PrintStream;
52: iload 9
54: invokevirtual #8 // Method java/io/PrintStream.println:(I)V
57: new #9 // class java/util/ArrayList
60: dup
61: invokespecial #10 // Method java/util/ArrayList."":()V
64: astore 10
66: new #11 // class com/jvm/bookdemo/z6/ClassCompileTest
69: dup
70: invokespecial #12 // Method "":()V
73: astore 11
75: aload 10
77: aload 11
79: invokeinterface #13, 2 // InterfaceMethod java/util/List.add:(Ljava/lang/Object;)Z
84: pop
85: new #14 // class java/lang/StringBuffer
88: dup
89: aload_1
90: invokespecial #15 // Method java/lang/StringBuffer."":(Ljava/lang/String;)V
93: astore 12
95: aload 12
97: aload_2
98: invokevirtual #16 // Method java/lang/StringBuffer.append:(Ljava/lang/String;)Ljava/lang/StringBuffer;
101: pop
102: aload 12
104: invokevirtual #17 // Method java/lang/StringBuffer.toString:()Ljava/lang/String;
107: areturn
LineNumberTable:
line 20: 0
line 21: 7
line 23: 14
line 24: 17
line 25: 21
line 26: 24
line 27: 27
line 28: 31
line 29: 49
line 32: 57
line 33: 66
line 34: 75
line 35: 85
line 36: 95
line 37: 102
LocalVariableTable:
Start Length Slot Name Signature
0 108 0 this Lcom/jvm/bookdemo/z6/ClassCompileTest;
0 108 1 paraStr Ljava/lang/String;
0 108 2 prefix Ljava/lang/String;
7 101 3 g Ljava/lang/Long;
17 91 4 a I
21 87 5 b I
24 84 6 c I
27 81 7 d I
31 77 8 e I
49 59 9 f I
66 42 10 list Ljava/util/List;
75 33 11 ct Lcom/jvm/bookdemo/z6/ClassCompileTest;
95 13 12 sb Ljava/lang/StringBuffer;
LocalVariableTypeTable:
Start Length Slot Name Signature
66 42 10 list Ljava/util/List;
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=3, locals=1, args_size=1
0: getstatic #6 // Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #18 // String 4E
5: bipush 16
7: invokestatic #19 // Method java/lang/Integer.parseInt:(Ljava/lang/String;I)I
10: invokevirtual #8 // Method java/io/PrintStream.println:(I)V
13: getstatic #6 // Field java/lang/System.out:Ljava/io/PrintStream;
16: bipush 33
18: invokestatic #20 // Method java/lang/Integer.toHexString:(I)Ljava/lang/String;
21: invokevirtual #21 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
24: getstatic #6 // Field java/lang/System.out:Ljava/io/PrintStream;
27: sipush 16385
30: invokestatic #20 // Method java/lang/Integer.toHexString:(I)Ljava/lang/String;
33: invokevirtual #21 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
36: return
LineNumberTable:
line 43: 0
line 44: 13
line 45: 24
line 46: 36
LocalVariableTable:
Start Length Slot Name Signature
0 37 0 args [Ljava/lang/String;
static {};
descriptor: ()V
flags: ACC_STATIC
Code:
stack=1, locals=0, args_size=0
0: ldc #22 // String 222
2: putstatic #23 // Field CONSTANT_PARAM:Ljava/lang/String;
5: bipush 96
7: putstatic #24 // Field INT_PARAM:I
10: return
LineNumberTable:
line 15: 0
line 16: 5
}
SourceFile: "ClassCompileTest.java"
public java.lang.String appendStr(java.lang.String, java.lang.String);
descriptor: (Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
flags: ACC_PUBLIC //方法表结构的前2个字节，ACC_PUBLIC代表方法为public
Code: //Code是方法表结构里的属性，对应 attribute_info的前2个字节attribute_name_index，指向常量池中code的索引（实例中就是#35）
stack=3, locals=13, args_size=3 //Stack=3代表栈帧深度为3（max_stack），locals=13（代表局部变量表需要的存储空间为Sloats为13个），args_size=3代表方法的参数为3个，分别为this，String类型，String类型
0: ldc2_w #3 // long 9223372036854775807l //ldc2_w 指令的含义是把long类型常量值从常量池中推送至栈顶
3: invokestatic #5 // Method java/lang/Long.valueOf:(J)Ljava/lang/Long; //调用静态方法，这里指的就是调用Long.valueOf 方法
6: astore_3 //将第4个引用类型（引用类型从LocalVariableTable下面，找到Slot列为3的名称，对应的name为g）本地变量推送至栈顶，即上面计算后的结果，推送至栈顶
7: getstatic #6 // Field java/lang/System.out:Ljava/io/PrintStream; //获取指定类的静态域，并将其压入栈顶。这里后面
10: aload_3 //将第4个引用类型（也就是LocalVariableTable下面的name为”g“的参数）推送至栈顶
11: invokevirtual #7 // Method java/io/PrintStream.println:(Ljava/lang/Object;)V //调用实例方法，调用的方法就是 java/io/PrintStream.println
14: iconst_1 //将int类型值1，推送至栈顶