Package org.springframework.asm

Class MethodVisitor

java.lang.Object
org.springframework.asm.MethodVisitor
Direct Known Subclasses:
LocalVariablesSorter, MethodVisitorTee
public abstract class MethodVisitor extends Object
A visitor to visit a Java method. The methods of this class must be called in the following order: ( visitParameter )* [ visitAnnotationDefault ] ( visitAnnotation | visitAnnotableParameterCount | visitParameterAnnotation | visitTypeAnnotation | visitAttribute )* [ visitCode ( visitFrame | visit<i>X</i>Insn | visitLabel | visitInsnAnnotation | visitTryCatchBlock | visitTryCatchAnnotation | visitLocalVariable | visitLocalVariableAnnotation | visitLineNumber | visitAttribute )* visitMaxs ] visitEnd. In addition, the visit<i>X</i>Insn and visitLabel methods must be called in the sequential order of the bytecode instructions of the visited code, visitInsnAnnotation must be called after the annotated instruction, visitTryCatchBlock must be called before the labels passed as arguments have been visited, visitTryCatchBlockAnnotation must be called after the corresponding try catch block has been visited, and the visitLocalVariable, visitLocalVariableAnnotation and visitLineNumber methods must be called after the labels passed as arguments have been visited. Finally, the visitAttribute method must be called before visitCode for non-code attributes, and after it for code attributes.
Author:
Eric Bruneton

  • Field Details

    • api

      protected final int api
      The ASM API version implemented by this visitor. The value of this field must be one of the ASMx values in Opcodes.

    • mv

      protected MethodVisitor mv
      The method visitor to which this visitor must delegate method calls. May be null.

  • Constructor Details

    • MethodVisitor

      protected MethodVisitor(int api)
      Constructs a new MethodVisitor.
      Parameters:
      api - the ASM API version implemented by this visitor. Must be one of the ASMx values in Opcodes.

    • MethodVisitor

      protected MethodVisitor(int api, MethodVisitor methodVisitor)
      Constructs a new MethodVisitor.
      Parameters:
      api - the ASM API version implemented by this visitor. Must be one of the ASMx values in Opcodes.
      methodVisitor - the method visitor to which this visitor must delegate method calls. May be null.

  • Method Details

    • getDelegate

      public MethodVisitor getDelegate()
      The method visitor to which this visitor must delegate method calls. May be null.
      Returns:
      the method visitor to which this visitor must delegate method calls, or null.

    • visitParameter

      public void visitParameter(String name, int access)
      Visits a parameter of this method.
      Parameters:
      name - parameter name or null if none is provided.
      access - the parameter's access flags, only ACC_FINAL, ACC_SYNTHETIC or/and ACC_MANDATED are allowed (see Opcodes).

    • visitAnnotationDefault

      public AnnotationVisitor visitAnnotationDefault()
      Visits the default value of this annotation interface method.
      Returns:
      a visitor to the visit the actual default value of this annotation interface method, or null if this visitor is not interested in visiting this default value. The 'name' parameters passed to the methods of this annotation visitor are ignored. Moreover, exactly one visit method must be called on this annotation visitor, followed by visitEnd.

    • visitAnnotation

      public AnnotationVisitor visitAnnotation(String descriptor, boolean visible)
      Visits an annotation of this method.
      Parameters:
      descriptor - the class descriptor of the annotation class.
      visible - true if the annotation is visible at runtime.
      Returns:
      a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.

    • visitTypeAnnotation

      public AnnotationVisitor visitTypeAnnotation(int typeRef, TypePath typePath, String descriptor, boolean visible)
      Visits an annotation on a type in the method signature.
      Parameters:
      typeRef - a reference to the annotated type. The sort of this type reference must be TypeReference.METHOD_TYPE_PARAMETER, TypeReference.METHOD_TYPE_PARAMETER_BOUND, TypeReference.METHOD_RETURN, TypeReference.METHOD_RECEIVER, TypeReference.METHOD_FORMAL_PARAMETER or TypeReference.THROWS. See TypeReference.
      typePath - the path to the annotated type argument, wildcard bound, array element type, or static inner type within 'typeRef'. May be null if the annotation targets 'typeRef' as a whole.
      descriptor - the class descriptor of the annotation class.
      visible - true if the annotation is visible at runtime.
      Returns:
      a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.

    • visitAnnotableParameterCount

      public void visitAnnotableParameterCount(int parameterCount, boolean visible)
      Visits the number of method parameters that can have annotations. By default (i.e. when this method is not called), all the method parameters defined by the method descriptor can have annotations.
      Parameters:
      parameterCount - the number of method parameters than can have annotations. This number must be less or equal than the number of parameter types in the method descriptor. It can be strictly less when a method has synthetic parameters and when these parameters are ignored when computing parameter indices for the purpose of parameter annotations (see https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.18).
      visible - true to define the number of method parameters that can have annotations visible at runtime, false to define the number of method parameters that can have annotations invisible at runtime.

    • visitParameterAnnotation

      public AnnotationVisitor visitParameterAnnotation(int parameter, String descriptor, boolean visible)
      Visits an annotation of a parameter this method.
      Parameters:
      parameter - the parameter index. This index must be strictly smaller than the number of parameters in the method descriptor, and strictly smaller than the parameter count specified in visitAnnotableParameterCount(int, boolean). Important note: a parameter index i is not required to correspond to the i'th parameter descriptor in the method descriptor, in particular in case of synthetic parameters (see https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.18).
      descriptor - the class descriptor of the annotation class.
      visible - true if the annotation is visible at runtime.
      Returns:
      a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.

    • visitAttribute

      public void visitAttribute(Attribute attribute)
      Visits a non standard attribute of this method.
      Parameters:
      attribute - an attribute.

    • visitCode

      public void visitCode()
      Starts the visit of the method's code, if any (i.e. non abstract method).

    • visitFrame

      public void visitFrame(int type, int numLocal, Object[] local, int numStack, Object[] stack)
      Visits the current state of the local variables and operand stack elements. This method must(*) be called just before any instruction i that follows an unconditional branch instruction such as GOTO or THROW, that is the target of a jump instruction, or that starts an exception handler block. The visited types must describe the values of the local variables and of the operand stack elements just before i is executed.

      (*) this is mandatory only for classes whose version is greater than or equal to Opcodes.V1_6.

      The frames of a method must be given either in expanded form, or in compressed form (all frames must use the same format, i.e. you must not mix expanded and compressed frames within a single method):
      • In expanded form, all frames must have the F_NEW type.
      • In compressed form, frames are basically "deltas" from the state of the previous frame:
        • Opcodes.F_SAME representing frame with exactly the same locals as the previous frame and with the empty stack.
        • Opcodes.F_SAME1 representing frame with exactly the same locals as the previous frame and with single value on the stack ( numStack is 1 and stack[0] contains value for the type of the stack item).
        • Opcodes.F_APPEND representing frame with current locals are the same as the locals in the previous frame, except that additional locals are defined ( numLocal is 1, 2 or 3 and local elements contains values representing added types).
        • Opcodes.F_CHOP representing frame with current locals are the same as the locals in the previous frame, except that the last 1-3 locals are absent and with the empty stack (numLocal is 1, 2 or 3).
        • Opcodes.F_FULL representing complete frame data.

      In both cases the first frame, corresponding to the method's parameters and access flags, is implicit and must not be visited. Also, it is illegal to visit two or more frames for the same code location (i.e., at least one instruction must be visited between two calls to visitFrame).
      Parameters:
      type - the type of this stack map frame. Must be Opcodes.F_NEW for expanded frames, or Opcodes.F_FULL, Opcodes.F_APPEND, Opcodes.F_CHOP, Opcodes.F_SAME or Opcodes.F_APPEND, Opcodes.F_SAME1 for compressed frames.
      numLocal - the number of local variables in the visited frame. Long and double values count for one variable.
      local - the local variable types in this frame. This array must not be modified. Primitive types are represented by Opcodes.TOP, Opcodes.INTEGER, Opcodes.FLOAT, Opcodes.LONG, Opcodes.DOUBLE, Opcodes.NULL or Opcodes.UNINITIALIZED_THIS (long and double are represented by a single element). Reference types are represented by String objects (representing internal names, see Type.getInternalName()), and uninitialized types by Label objects (this label designates the NEW instruction that created this uninitialized value).
      numStack - the number of operand stack elements in the visited frame. Long and double values count for one stack element.
      stack - the operand stack types in this frame. This array must not be modified. Its content has the same format as the "local" array.
      Throws:
      IllegalStateException - if a frame is visited just after another one, without any instruction between the two (unless this frame is a Opcodes#F_SAME frame, in which case it is silently ignored).

    • visitInsn

      public void visitInsn(int opcode)
      Visits a zero operand instruction.
      Parameters:
      opcode - the opcode of the instruction to be visited. This opcode is either NOP, ACONST_NULL, ICONST_M1, ICONST_0, ICONST_1, ICONST_2, ICONST_3, ICONST_4, ICONST_5, LCONST_0, LCONST_1, FCONST_0, FCONST_1, FCONST_2, DCONST_0, DCONST_1, IALOAD, LALOAD, FALOAD, DALOAD, AALOAD, BALOAD, CALOAD, SALOAD, IASTORE, LASTORE, FASTORE, DASTORE, AASTORE, BASTORE, CASTORE, SASTORE, POP, POP2, DUP, DUP_X1, DUP_X2, DUP2, DUP2_X1, DUP2_X2, SWAP, IADD, LADD, FADD, DADD, ISUB, LSUB, FSUB, DSUB, IMUL, LMUL, FMUL, DMUL, IDIV, LDIV, FDIV, DDIV, IREM, LREM, FREM, DREM, INEG, LNEG, FNEG, DNEG, ISHL, LSHL, ISHR, LSHR, IUSHR, LUSHR, IAND, LAND, IOR, LOR, IXOR, LXOR, I2L, I2F, I2D, L2I, L2F, L2D, F2I, F2L, F2D, D2I, D2L, D2F, I2B, I2C, I2S, LCMP, FCMPL, FCMPG, DCMPL, DCMPG, IRETURN, LRETURN, FRETURN, DRETURN, ARETURN, RETURN, ARRAYLENGTH, ATHROW, MONITORENTER, or MONITOREXIT.

    • visitIntInsn

      public void visitIntInsn(int opcode, int operand)
      Visits an instruction with a single int operand.
      Parameters:
      opcode - the opcode of the instruction to be visited. This opcode is either BIPUSH, SIPUSH or NEWARRAY.
      operand - the operand of the instruction to be visited.
      When opcode is BIPUSH, operand value should be between Byte.MIN_VALUE and Byte.MAX_VALUE.
      When opcode is SIPUSH, operand value should be between Short.MIN_VALUE and Short.MAX_VALUE.
      When opcode is NEWARRAY, operand value should be one of Opcodes.T_BOOLEAN, Opcodes.T_CHAR, Opcodes.T_FLOAT, Opcodes.T_DOUBLE, Opcodes.T_BYTE, Opcodes.T_SHORT, Opcodes.T_INT or Opcodes.T_LONG.

    • visitVarInsn

      public void visitVarInsn(int opcode, int varIndex)
      Visits a local variable instruction. A local variable instruction is an instruction that loads or stores the value of a local variable.
      Parameters:
      opcode - the opcode of the local variable instruction to be visited. This opcode is either ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE or RET.
      varIndex - the operand of the instruction to be visited. This operand is the index of a local variable.

    • visitTypeInsn

      public void visitTypeInsn(int opcode, String type)
      Visits a type instruction. A type instruction is an instruction that takes the internal name of a class as parameter (see Type.getInternalName()).
      Parameters:
      opcode - the opcode of the type instruction to be visited. This opcode is either NEW, ANEWARRAY, CHECKCAST or INSTANCEOF.
      type - the operand of the instruction to be visited. This operand must be the internal name of an object or array class (see Type.getInternalName()).

    • visitFieldInsn

      public void visitFieldInsn(int opcode, String owner, String name, String descriptor)
      Visits a field instruction. A field instruction is an instruction that loads or stores the value of a field of an object.
      Parameters:
      opcode - the opcode of the type instruction to be visited. This opcode is either GETSTATIC, PUTSTATIC, GETFIELD or PUTFIELD.
      owner - the internal name of the field's owner class (see Type.getInternalName()).
      name - the field's name.
      descriptor - the field's descriptor (see Type).

    • visitMethodInsn

      @Deprecated public void visitMethodInsn(int opcode, String owner, String name, String descriptor)
      Deprecated.
      use visitMethodInsn(int, String, String, String, boolean) instead.
      Visits a method instruction. A method instruction is an instruction that invokes a method.
      Parameters:
      opcode - the opcode of the type instruction to be visited. This opcode is either INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC or INVOKEINTERFACE.
      owner - the internal name of the method's owner class (see Type.getInternalName()).
      name - the method's name.
      descriptor - the method's descriptor (see Type).

    • visitMethodInsn

      public void visitMethodInsn(int opcode, String owner, String name, String descriptor, boolean isInterface)
      Visits a method instruction. A method instruction is an instruction that invokes a method.
      Parameters:
      opcode - the opcode of the type instruction to be visited. This opcode is either INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC or INVOKEINTERFACE.
      owner - the internal name of the method's owner class (see Type.getInternalName()).
      name - the method's name.
      descriptor - the method's descriptor (see Type).
      isInterface - if the method's owner class is an interface.

    • visitInvokeDynamicInsn

      public void visitInvokeDynamicInsn(String name, String descriptor, Handle bootstrapMethodHandle, Object... bootstrapMethodArguments)
      Visits an invokedynamic instruction.
      Parameters:
      name - the method's name.
      descriptor - the method's descriptor (see Type).
      bootstrapMethodHandle - the bootstrap method.
      bootstrapMethodArguments - the bootstrap method constant arguments. Each argument must be an Integer, Float, Long, Double, String, Type, Handle or ConstantDynamic value. This method is allowed to modify the content of the array so a caller should expect that this array may change.

    • visitJumpInsn

      public void visitJumpInsn(int opcode, Label label)
      Visits a jump instruction. A jump instruction is an instruction that may jump to another instruction.
      Parameters:
      opcode - the opcode of the type instruction to be visited. This opcode is either IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE, IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE, GOTO, JSR, IFNULL or IFNONNULL.
      label - the operand of the instruction to be visited. This operand is a label that designates the instruction to which the jump instruction may jump.

    • visitLabel

      public void visitLabel(Label label)
      Visits a label. A label designates the instruction that will be visited just after it.
      Parameters:
      label - a Label object.

    • visitLdcInsn

      public void visitLdcInsn(Object value)
      Visits a LDC instruction. Note that new constant types may be added in future versions of the Java Virtual Machine. To easily detect new constant types, implementations of this method should check for unexpected constant types, like this: 
       if (cst instanceof Integer) {
     // ...
 } else if (cst instanceof Float) {
     // ...
 } else if (cst instanceof Long) {
     // ...
 } else if (cst instanceof Double) {
     // ...
 } else if (cst instanceof String) {
     // ...
 } else if (cst instanceof Type) {
     int sort = ((Type) cst).getSort();
     if (sort == Type.OBJECT) {
         // ...
     } else if (sort == Type.ARRAY) {
         // ...
     } else if (sort == Type.METHOD) {
         // ...
     } else {
         // throw an exception
     }
 } else if (cst instanceof Handle) {
     // ...
 } else if (cst instanceof ConstantDynamic) {
     // ...
 } else {
     // throw an exception
 }
      Parameters:
      value - the constant to be loaded on the stack. This parameter must be a non null Integer, a Float, a Long, a Double, a String, a Type of OBJECT or ARRAY sort for .class constants, for classes whose version is 49, a Type of METHOD sort for MethodType, a Handle for MethodHandle constants, for classes whose version is 51 or a ConstantDynamic for a constant dynamic for classes whose version is 55.

    • visitIincInsn

      public void visitIincInsn(int varIndex, int increment)
      Visits an IINC instruction.
      Parameters:
      varIndex - index of the local variable to be incremented.
      increment - amount to increment the local variable by.

    • visitTableSwitchInsn

      public void visitTableSwitchInsn(int min, int max, Label dflt, Label... labels)
      Visits a TABLESWITCH instruction.
      Parameters:
      min - the minimum key value.
      max - the maximum key value.
      dflt - beginning of the default handler block.
      labels - beginnings of the handler blocks. labels[i] is the beginning of the handler block for the min + i key.

    • visitLookupSwitchInsn

      public void visitLookupSwitchInsn(Label dflt, int[] keys, Label[] labels)
      Visits a LOOKUPSWITCH instruction.
      Parameters:
      dflt - beginning of the default handler block.
      keys - the values of the keys.
      labels - beginnings of the handler blocks. labels[i] is the beginning of the handler block for the keys[i] key.

    • visitMultiANewArrayInsn

      public void visitMultiANewArrayInsn(String descriptor, int numDimensions)
      Visits a MULTIANEWARRAY instruction.
      Parameters:
      descriptor - an array type descriptor (see Type).
      numDimensions - the number of dimensions of the array to allocate.

    • visitInsnAnnotation

      public AnnotationVisitor visitInsnAnnotation(int typeRef, TypePath typePath, String descriptor, boolean visible)
      Visits an annotation on an instruction. This method must be called just after the annotated instruction. It can be called several times for the same instruction.
      Parameters:
      typeRef - a reference to the annotated type. The sort of this type reference must be TypeReference.INSTANCEOF, TypeReference.NEW, TypeReference.CONSTRUCTOR_REFERENCE, TypeReference.METHOD_REFERENCE, TypeReference.CAST, TypeReference.CONSTRUCTOR_INVOCATION_TYPE_ARGUMENT, TypeReference.METHOD_INVOCATION_TYPE_ARGUMENT, TypeReference.CONSTRUCTOR_REFERENCE_TYPE_ARGUMENT, or TypeReference.METHOD_REFERENCE_TYPE_ARGUMENT. See TypeReference.
      typePath - the path to the annotated type argument, wildcard bound, array element type, or static inner type within 'typeRef'. May be null if the annotation targets 'typeRef' as a whole.
      descriptor - the class descriptor of the annotation class.
      visible - true if the annotation is visible at runtime.
      Returns:
      a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.

    • visitTryCatchBlock

      public void visitTryCatchBlock(Label start, Label end, Label handler, String type)
      Visits a try catch block.
      Parameters:
      start - the beginning of the exception handler's scope (inclusive).
      end - the end of the exception handler's scope (exclusive).
      handler - the beginning of the exception handler's code.
      type - the internal name of the type of exceptions handled by the handler (see Type.getInternalName()), or null to catch any exceptions (for "finally" blocks).
      Throws:
      IllegalArgumentException - if one of the labels has already been visited by this visitor (by the visitLabel(org.springframework.asm.Label) method).

    • visitTryCatchAnnotation

      public AnnotationVisitor visitTryCatchAnnotation(int typeRef, TypePath typePath, String descriptor, boolean visible)
      Visits an annotation on an exception handler type. This method must be called after the visitTryCatchBlock(org.springframework.asm.Label, org.springframework.asm.Label, org.springframework.asm.Label, java.lang.String) for the annotated exception handler. It can be called several times for the same exception handler.
      Parameters:
      typeRef - a reference to the annotated type. The sort of this type reference must be TypeReference.EXCEPTION_PARAMETER. See TypeReference.
      typePath - the path to the annotated type argument, wildcard bound, array element type, or static inner type within 'typeRef'. May be null if the annotation targets 'typeRef' as a whole.
      descriptor - the class descriptor of the annotation class.
      visible - true if the annotation is visible at runtime.
      Returns:
      a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.

    • visitLocalVariable

      public void visitLocalVariable(String name, String descriptor, String signature, Label start, Label end, int index)
      Visits a local variable declaration.
      Parameters:
      name - the name of a local variable.
      descriptor - the type descriptor of this local variable.
      signature - the type signature of this local variable. May be null if the local variable type does not use generic types.
      start - the first instruction corresponding to the scope of this local variable (inclusive).
      end - the last instruction corresponding to the scope of this local variable (exclusive).
      index - the local variable's index.
      Throws:
      IllegalArgumentException - if one of the labels has not already been visited by this visitor (by the visitLabel(org.springframework.asm.Label) method).

    • visitLocalVariableAnnotation

      public AnnotationVisitor visitLocalVariableAnnotation(int typeRef, TypePath typePath, Label[] start, Label[] end, int[] index, String descriptor, boolean visible)
      Visits an annotation on a local variable type.
      Parameters:
      typeRef - a reference to the annotated type. The sort of this type reference must be TypeReference.LOCAL_VARIABLE or TypeReference.RESOURCE_VARIABLE. See TypeReference.
      typePath - the path to the annotated type argument, wildcard bound, array element type, or static inner type within 'typeRef'. May be null if the annotation targets 'typeRef' as a whole.
      start - the fist instructions corresponding to the continuous ranges that make the scope of this local variable (inclusive).
      end - the last instructions corresponding to the continuous ranges that make the scope of this local variable (exclusive). This array must have the same size as the 'start' array.
      index - the local variable's index in each range. This array must have the same size as the 'start' array.
      descriptor - the class descriptor of the annotation class.
      visible - true if the annotation is visible at runtime.
      Returns:
      a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.

    • visitLineNumber

      public void visitLineNumber(int line, Label start)
      Visits a line number declaration.
      Parameters:
      line - a line number. This number refers to the source file from which the class was compiled.
      start - the first instruction corresponding to this line number.
      Throws:
      IllegalArgumentException - if start has not already been visited by this visitor (by the visitLabel(org.springframework.asm.Label) method).

    • visitMaxs

      public void visitMaxs(int maxStack, int maxLocals)
      Visits the maximum stack size and the maximum number of local variables of the method.
      Parameters:
      maxStack - maximum stack size of the method.
      maxLocals - maximum number of local variables for the method.

    • visitEnd

      public void visitEnd()
      Visits the end of the method. This method, which is the last one to be called, is used to inform the visitor that all the annotations and attributes of the method have been visited.