本文属于[Java ASM系列一：Core API](https://blog.51cto.com/lsieun/2924583)当中的一篇。 `Opcodes`是一个接口，它定义了许多字段。这些字段主要是在`ClassVisitor.visitXxx()`和`MethodVisitor.visitXxx()`方法中使用。 ## 1. ClassVisitor ### 1.1 ASM Version 字段含义：`Opcodes.ASM4`~`Opcodes.ASM9`标识了ASM的版本信息。 应用场景：用于创建具体的`ClassVisitor`实例，例如`ClassVisitor(int api, ClassVisitor classVisitor)`中的`api`参数。 ```java public interface Opcodes { // ASM API versions. int ASM4 = 4 << 16 | 0 << 8; int ASM5 = 5 << 16 | 0 << 8; int ASM6 = 6 << 16 | 0 << 8; int ASM7 = 7 << 16 | 0 << 8; int ASM8 = 8 << 16 | 0 << 8; int ASM9 = 9 << 16 | 0 << 8; } ``` ### 1.2 Java Version 字段含义：`Opcodes.V1_1`~`Opcodes.V16`标识了`.class`文件的版本信息。 应用场景：用于`ClassVisitor.visit(int version, int access, ...)`的`version`参数。 ```java public interface Opcodes { // Java ClassFile versions // (the minor version is stored in the 16 most significant bits, and // the major version in the 16 least significant bits). int V1_1 = 3 << 16 | 45; int V1_2 = 0 << 16 | 46; int V1_3 = 0 << 16 | 47; int V1_4 = 0 << 16 | 48; int V1_5 = 0 << 16 | 49; int V1_6 = 0 << 16 | 50; int V1_7 = 0 << 16 | 51; int V1_8 = 0 << 16 | 52; int V9 = 0 << 16 | 53; int V10 = 0 << 16 | 54; int V11 = 0 << 16 | 55; int V12 = 0 << 16 | 56; int V13 = 0 << 16 | 57; int V14 = 0 << 16 | 58; int V15 = 0 << 16 | 59; int V16 = 0 << 16 | 60; } ``` ### 1.3 Access Flags 字段含义：`Opcodes.ACC_PUBLIC`~`Opcodes.ACC_MODULE`标识了Class、Field、Method的访问标识（Access Flag）。 应用场景： - `ClassVisitor.visit(int version, int access, ...)`的`access`参数。 - `ClassVisitor.visitField(int access, String name, ...)`的`access`参数。 - `ClassVisitor.visitMethod(int access, String name, ...)`的`access`参数。 ```java public interface Opcodes { int ACC_PUBLIC = 0x0001; // class, field, method int ACC_PRIVATE = 0x0002; // class, field, method int ACC_PROTECTED = 0x0004; // class, field, method int ACC_STATIC = 0x0008; // field, method int ACC_FINAL = 0x0010; // class, field, method, parameter int ACC_SUPER = 0x0020; // class int ACC_SYNCHRONIZED = 0x0020; // method int ACC_OPEN = 0x0020; // module int ACC_TRANSITIVE = 0x0020; // module requires int ACC_VOLATILE = 0x0040; // field int ACC_BRIDGE = 0x0040; // method int ACC_STATIC_PHASE = 0x0040; // module requires int ACC_VARARGS = 0x0080; // method int ACC_TRANSIENT = 0x0080; // field int ACC_NATIVE = 0x0100; // method int ACC_INTERFACE = 0x0200; // class int ACC_ABSTRACT = 0x0400; // class, method int ACC_STRICT = 0x0800; // method int ACC_SYNTHETIC = 0x1000; // class, field, method, parameter, module * int ACC_ANNOTATION = 0x2000; // class int ACC_ENUM = 0x4000; // class(?) field inner int ACC_MANDATED = 0x8000; // field, method, parameter, module, module * int ACC_MODULE = 0x8000; // class } ``` ## 2. MethodVisitor ### 2.1 frame 字段含义：`Opcodes.F_NEW`~`Opcodes.F_SAME1`标识了frame的状态，`Opcodes.TOP`~`Opcodes.UNINITIALIZED_THIS`标识了frame中某一个数据项的具体类型。 应用场景： - `Opcodes.F_NEW`~`Opcodes.F_SAME1`用在`MethodVisitor.visitFrame(int type, int numLocal, Object[] local, int numStack, Object[] stack)`方法中的`type`参数。 - `Opcodes.TOP`~`Opcodes.UNINITIALIZED_THIS`用在`MethodVisitor.visitFrame(int type, int numLocal, Object[] local, int numStack, Object[] stack)`方法中的`local`参数和`stack`参数。 ```java public interface Opcodes { // ASM specific stack map frame types, used in {@link ClassVisitor#visitFrame}. int F_NEW = -1; int F_FULL = 0; int F_APPEND = 1; int F_CHOP = 2; int F_SAME = 3; int F_SAME1 = 4; // Standard stack map frame element types, used in {@link ClassVisitor#visitFrame}. Integer TOP = Frame.ITEM_TOP; Integer INTEGER = Frame.ITEM_INTEGER; Integer FLOAT = Frame.ITEM_FLOAT; Integer DOUBLE = Frame.ITEM_DOUBLE; Integer LONG = Frame.ITEM_LONG; Integer NULL = Frame.ITEM_NULL; Integer UNINITIALIZED_THIS = Frame.ITEM_UNINITIALIZED_THIS; } ``` ### 2.2 opcodes 字段含义：`Opcodes.NOP`~`Opcodes.IFNONNULL`表示opcode的值。 应用场景：在`MethodVisitor.visitXxxInsn(opcode)`方法中的`opcode`参数中使用。 ```java public interface Opcodes { int NOP = 0; // visitInsn int ACONST_NULL = 1; // - int ICONST_M1 = 2; // - int ICONST_0 = 3; // - int ICONST_1 = 4; // - int ICONST_2 = 5; // - int ICONST_3 = 6; // - int ICONST_4 = 7; // - int ICONST_5 = 8; // - int LCONST_0 = 9; // - int LCONST_1 = 10; // - int FCONST_0 = 11; // - int FCONST_1 = 12; // - int FCONST_2 = 13; // - int DCONST_0 = 14; // - int DCONST_1 = 15; // - int BIPUSH = 16; // visitIntInsn int SIPUSH = 17; // - int LDC = 18; // visitLdcInsn int ILOAD = 21; // visitVarInsn int LLOAD = 22; // - int FLOAD = 23; // - int DLOAD = 24; // - int ALOAD = 25; // - int IALOAD = 46; // visitInsn int LALOAD = 47; // - int FALOAD = 48; // - int DALOAD = 49; // - int AALOAD = 50; // - int BALOAD = 51; // - int CALOAD = 52; // - int SALOAD = 53; // - int ISTORE = 54; // visitVarInsn int LSTORE = 55; // - int FSTORE = 56; // - int DSTORE = 57; // - int ASTORE = 58; // - int IASTORE = 79; // visitInsn int LASTORE = 80; // - int FASTORE = 81; // - int DASTORE = 82; // - int AASTORE = 83; // - int BASTORE = 84; // - int CASTORE = 85; // - int SASTORE = 86; // - int POP = 87; // - int POP2 = 88; // - int DUP = 89; // - int DUP_X1 = 90; // - int DUP_X2 = 91; // - int DUP2 = 92; // - int DUP2_X1 = 93; // - int DUP2_X2 = 94; // - int SWAP = 95; // - int IADD = 96; // - int LADD = 97; // - int FADD = 98; // - int DADD = 99; // - int ISUB = 100; // - int LSUB = 101; // - int FSUB = 102; // - int DSUB = 103; // - int IMUL = 104; // - int LMUL = 105; // - int FMUL = 106; // - int DMUL = 107; // - int IDIV = 108; // - int LDIV = 109; // - int FDIV = 110; // - int DDIV = 111; // - int IREM = 112; // - int LREM = 113; // - int FREM = 114; // - int DREM = 115; // - int INEG = 116; // - int LNEG = 117; // - int FNEG = 118; // - int DNEG = 119; // - int ISHL = 120; // - int LSHL = 121; // - int ISHR = 122; // - int LSHR = 123; // - int IUSHR = 124; // - int LUSHR = 125; // - int IAND = 126; // - int LAND = 127; // - int IOR = 128; // - int LOR = 129; // - int IXOR = 130; // - int LXOR = 131; // - int IINC = 132; // visitIincInsn int I2L = 133; // visitInsn int I2F = 134; // - int I2D = 135; // - int L2I = 136; // - int L2F = 137; // - int L2D = 138; // - int F2I = 139; // - int F2L = 140; // - int F2D = 141; // - int D2I = 142; // - int D2L = 143; // - int D2F = 144; // - int I2B = 145; // - int I2C = 146; // - int I2S = 147; // - int LCMP = 148; // - int FCMPL = 149; // - int FCMPG = 150; // - int DCMPL = 151; // - int DCMPG = 152; // - int IFEQ = 153; // visitJumpInsn int IFNE = 154; // - int IFLT = 155; // - int IFGE = 156; // - int IFGT = 157; // - int IFLE = 158; // - int IF_ICMPEQ = 159; // - int IF_ICMPNE = 160; // - int IF_ICMPLT = 161; // - int IF_ICMPGE = 162; // - int IF_ICMPGT = 163; // - int IF_ICMPLE = 164; // - int IF_ACMPEQ = 165; // - int IF_ACMPNE = 166; // - int GOTO = 167; // - int JSR = 168; // - int RET = 169; // visitVarInsn int TABLESWITCH = 170; // visiTableSwitchInsn int LOOKUPSWITCH = 171; // visitLookupSwitch int IRETURN = 172; // visitInsn int LRETURN = 173; // - int FRETURN = 174; // - int DRETURN = 175; // - int ARETURN = 176; // - int RETURN = 177; // - int GETSTATIC = 178; // visitFieldInsn int PUTSTATIC = 179; // - int GETFIELD = 180; // - int PUTFIELD = 181; // - int INVOKEVIRTUAL = 182; // visitMethodInsn int INVOKESPECIAL = 183; // - int INVOKESTATIC = 184; // - int INVOKEINTERFACE = 185; // - int INVOKEDYNAMIC = 186; // visitInvokeDynamicInsn int NEW = 187; // visitTypeInsn int NEWARRAY = 188; // visitIntInsn int ANEWARRAY = 189; // visitTypeInsn int ARRAYLENGTH = 190; // visitInsn int ATHROW = 191; // - int CHECKCAST = 192; // visitTypeInsn int INSTANCEOF = 193; // - int MONITORENTER = 194; // visitInsn int MONITOREXIT = 195; // - int MULTIANEWARRAY = 197; // visitMultiANewArrayInsn int IFNULL = 198; // visitJumpInsn int IFNONNULL = 199; // - } ``` ### 2.3 opcode: newarray 字段含义：`Opcodes.T_BOOLEAN`~`Opcodes.T_LONG`表示数组的类型。 应用场景：对于`MethodVisitor.visitIntInsn(opcode, operand)`方法，当`opcode`为`NEWARRAY`时，`operand`参数中使用。 ```java public interface Opcodes { // Possible values for the type operand of the NEWARRAY instruction. int T_BOOLEAN = 4; int T_CHAR = 5; int T_FLOAT = 6; int T_DOUBLE = 7; int T_BYTE = 8; int T_SHORT = 9; int T_INT = 10; int T_LONG = 11; } ``` ```java public class HelloWorld { public void test() { byte[] bytes = new byte[10]; } } ``` ### 2.4 opcode: invokedynamic 字段含义：`Opcodes.H_GETFIELD`~`Opcodes.H_INVOKEINTERFACE`表示MethodHandle的类型。 应用场景：在创建`Handle(int tag, String owner, String name, String descriptor, boolean isInterface)`时，`tag`参数中使用；而该`Handle`实例会在`MethodVisitor.visitInvokeDynamicInsn()`方法使用到。 ```java public interface Opcodes { // Possible values for the reference_kind field of CONSTANT_MethodHandle_info structures. int H_GETFIELD = 1; int H_GETSTATIC = 2; int H_PUTFIELD = 3; int H_PUTSTATIC = 4; int H_INVOKEVIRTUAL = 5; int H_INVOKESTATIC = 6; int H_INVOKESPECIAL = 7; int H_NEWINVOKESPECIAL = 8; int H_INVOKEINTERFACE = 9; } ``` ```java import java.util.function.BiFunction; public class HelloWorld { public void test() { BiFunction<Integer, Integer, Integer> func = Math::max; } } ``` ## 3. 总结 本文主要对`Opcodes`接口里定义的字段进行介绍，内容总结如下： - 第一点，在`Opcodes`类定义的字段，主要应用于`ClassVisitor`和`MethodVisitor`类的`visitXxx()`方法。 - 第二点，记忆方法。由于`Opcodes`类定义的字段很多，我们可以分成不同的批次和类别来进行理解，慢慢去掌握。