Java Class Format

CLASS FORMAT

ClassFile {  
  u4               magic;  
  u2               minor_version;  
  u2               major_version;  
  u2               constant_pool_count;  
  cp_info          constant_pool[constant_pool_count - 1];  
  u2               access_flags;  
  u2               this_class;  
  u2               super_class;  
  u2               interfaces_count;  
  u2               interfaces[interfaces_count];  
  u2               fields_count;  
  field_info       fields[fields_count];  
  u2               methods_count;  
  method_info      methods[methods_count];  
  u2               attributes_count;  
  attribute_info   attributes[attributes_count];  
} 

cp_info {
  u1 tag;
  u2 name_index;
}

field_info {
  u2 access_flags; 
  u2 name_index; 
  u2 descriptor_index; 
  u2 attributes_count; 
  attribute_info attributes[attributes_count];
}

method_info {
  u2 access_flags;
  u2 name_index;
  u2 descriptor_index;
  u2 attributes_count;
  attribute_info attributes[attributes_count];
}

attribute_info {
  u2 attribute_name_index;
  u4 attribute_length;
  u1 info[attribute_length];
}

Constant Type

Type	Tag
CONSTANT_Utf8	1
CONSTANT_Integer	3
CONSTANT_Float	4
CONSTANT_Long	5
CONSTANT_Double	6
CONSTANT_Class	7
CONSTANT_String	8
CONSTANT_Fieldref	9
CONSTANT_Methodref	10
CONSTANT_InterfaceMethodref	11
CONSTANT_NameAndType	12
CONSTANT_MethodHandle	15
CONSTANT_MethodType	16
CONSTANT_InvokeDynamic	18

Constant Type Info

CONSTANT_Utf8_info {  
   u1 tag;  
   u2 length;  
   u1 bytes[length];  
} 

CONSTANT_Integer_info {  
   u1 tag;  
   u4 bytes;  
} 

CONSTANT_Float_info {  
   u1 tag;  
   u4 bytes;  
} 

CONSTANT_Long_info {  
   u1 tag;  
   u4 high_bytes;  
   u4 low_bytes;  
} 

CONSTANT_Double_info {  
   u1 tag;  
   u4 high_bytes;  
   u4 low_bytes;  
} 

CONSTANT_Class_info {  
   u1 tag;  
   u2 name_index;  
} 

CONSTANT_String_info {  
   u1 tag;  
   u2 string_index;  
} 

CONSTANT_Fieldref_info {  
   u1 tag;  
   u2 class_index;  
   u2 name_and_type_index;  
} 

CONSTANT_Methodref_info {  
   u1 tag;  
   u2 class_index;  
   u2 name_and_type_index;  
} 

CONSTANT_InterfaceMethodref_info {  
   u1 tag;  
   u2 class_index;  
   u2 name_and_type_index;  
} 

CONSTANT_NameAndType_info {  
   u1 tag;  
   u2 name_index;  
   u2 descriptor_index;  
} 

CONSTANT_InvokeDynamic_info {
   u1 tag;
   u2 bootstrap_method_attr_index;
   u2 name_and_type_index;
}

ACCESS_FLAGS

Name	Value	Desc	-
ACC_PUBLIC	0x0001	public类型	所有类型
ACC_FINAL	0x0010	final类型	类
ACC_SUPER	0x0020	使用新的invokespecial语义	类和接口
ACC_INTERFACE	0x0200	接口类型	接口
ACC_ABSTRACT	0x0400	抽象类型	类和接口
ACC_SYNTHETIC	0x1000	该类不由用户代码生成	所有类型
ACC_ANNOTATION	0x2000	注解类型	注解
ACC_ENUM	0x4000	枚举类型	枚举