Package org.objectweb.asm.commons

Class AdviceAdapter

java.lang.Object
org.objectweb.asm.MethodVisitor
org.objectweb.asm.commons.LocalVariablesSorter
org.objectweb.asm.commons.GeneratorAdapter
org.objectweb.asm.commons.AdviceAdapter
All Implemented Interfaces:
Opcodes
public abstract class AdviceAdapter extends GeneratorAdapter implements Opcodes
A MethodVisitor to insert before, after and around advices in methods and constructors. For constructors, the code keeps track of the elements on the stack and in local variables in order to detect when the super class constructor is called (note that there can be multiple such calls in different branches). onMethodEnter is called after each super class constructor call, because the object cannot be used before it is properly initialized.

Note: this adapter does not work for arbitrary constructors if stack map frames are not present (if they are, it supports arbitrary valid code). Instead, it assumes that the code has been produced by a Java compiler. In particular it assumes that, in constructors:

  • the uninitialized instance is in local variable 0,
  • the uninitialized instance is never copied into another local variable,
  • there are no backward jumps when the stack map frame contains the uninitialized instance.

In these hypotheses are not true, and if there are no stack map frames, onMethodEnter might not be called at all, or might be called at the wrong place.

  • Field Details

    • methodAccess

      protected int methodAccess
      The access flags of the visited method.

    • methodDesc

      protected String methodDesc
      The descriptor of the visited method.

  • Constructor Details

    • AdviceAdapter

      protected AdviceAdapter(int api, MethodVisitor methodVisitor, int access, String name, String descriptor)
      Constructs a new AdviceAdapter.
      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 adapter delegates calls.
      access - the method's access flags (see Opcodes).
      name - the method's name.
      descriptor - the method's descriptor (see Type).

  • Method Details

    • setComputeLimits

      public void setComputeLimits(int maxBytes)
      Sets the maximum number of bytes which can be allocated by this adapter.

      The default limit should be sufficient for any "normal" class. You only need to set a new limit if this adapter throws a LimitExceededException on some of your classes.

      Parameters:
      maxBytes - the maximum number of bytes which can be allocated. Not all object instantiations are tracked (and garbage collection is ignored), but the most important ones are. The default value, 1MB, is more than one hundred times larger than the memory used for any constructor in the java.* modules of the JDK (this adapter does not do any allocations for methods).

    • visitCode

      public void visitCode()
      Description copied from class: MethodVisitor
      Starts the visit of the method's code, if any (i.e. non abstract method).
      Overrides:
      visitCode in class MethodVisitor

    • visitLabel

      public void visitLabel(Label label)
      Description copied from class: MethodVisitor
      Visits a label. A label designates the instruction that will be visited just after it.
      Overrides:
      visitLabel in class MethodVisitor
      Parameters:
      label - a Label object.

    • visitFrame

      public void visitFrame(int type, int numLocal, Object[] local, int numStack, Object[] stack)
      Description copied from class: MethodVisitor
      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).
      Overrides:
      visitFrame in class LocalVariablesSorter
      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.

    • visitInsn

      public void visitInsn(int opcode)
      Description copied from class: MethodVisitor
      Visits a zero operand instruction.
      Overrides:
      visitInsn in class MethodVisitor
      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.

    • visitVarInsn

      public void visitVarInsn(int opcode, int varIndex)
      Description copied from class: MethodVisitor
      Visits a local variable instruction. A local variable instruction is an instruction that loads or stores the value of a local variable.
      Overrides:
      visitVarInsn in class LocalVariablesSorter
      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.

    • visitFieldInsn

      public void visitFieldInsn(int opcode, String owner, String name, String descriptor)
      Description copied from class: MethodVisitor
      Visits a field instruction. A field instruction is an instruction that loads or stores the value of a field of an object.
      Overrides:
      visitFieldInsn in class MethodVisitor
      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).

    • visitIntInsn

      public void visitIntInsn(int opcode, int operand)
      Description copied from class: MethodVisitor
      Visits an instruction with a single int operand.
      Overrides:
      visitIntInsn in class MethodVisitor
      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.

    • visitLdcInsn

      public void visitLdcInsn(Object value)
      Description copied from class: MethodVisitor
      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
 }
      Overrides:
      visitLdcInsn in class MethodVisitor
      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.

    • visitMultiANewArrayInsn

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

    • visitTypeInsn

      public void visitTypeInsn(int opcode, String type)
      Description copied from class: MethodVisitor
      Visits a type instruction. A type instruction is an instruction that takes the internal name of a class as parameter (see Type.getInternalName()).
      Overrides:
      visitTypeInsn in class MethodVisitor
      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()).

    • visitMethodInsn

      public void visitMethodInsn(int opcodeAndSource, String owner, String name, String descriptor, boolean isInterface)
      Description copied from class: MethodVisitor
      Visits a method instruction. A method instruction is an instruction that invokes a method.
      Overrides:
      visitMethodInsn in class MethodVisitor
      Parameters:
      opcodeAndSource - 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)
      Description copied from class: MethodVisitor
      Visits an invokedynamic instruction.
      Overrides:
      visitInvokeDynamicInsn in class MethodVisitor
      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)
      Description copied from class: MethodVisitor
      Visits a jump instruction. A jump instruction is an instruction that may jump to another instruction.
      Overrides:
      visitJumpInsn in class MethodVisitor
      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.

    • visitLookupSwitchInsn

      public void visitLookupSwitchInsn(Label dflt, int[] keys, Label[] labels)
      Description copied from class: MethodVisitor
      Visits a LOOKUPSWITCH instruction.
      Overrides:
      visitLookupSwitchInsn in class MethodVisitor
      Parameters:
      dflt - beginning of the default handler block.
      keys - the values of the keys. Keys must be sorted in increasing order.
      labels - beginnings of the handler blocks. labels[i] is the beginning of the handler block for the keys[i] key.

    • visitTableSwitchInsn

      public void visitTableSwitchInsn(int min, int max, Label dflt, Label... labels)
      Description copied from class: MethodVisitor
      Visits a TABLESWITCH instruction.
      Overrides:
      visitTableSwitchInsn in class MethodVisitor
      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.

    • visitTryCatchBlock

      public void visitTryCatchBlock(Label start, Label end, Label handler, String type)
      Description copied from class: MethodVisitor
      Visits a try catch block.
      Overrides:
      visitTryCatchBlock in class MethodVisitor
      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).

    • onMethodEnter

      protected void onMethodEnter()
      Generates the "before" advice for the visited method. The default implementation of this method does nothing. Subclasses can use or change all the local variables, but should not change state of the stack. This method is called at the beginning of the method or after super class constructor has been called (in constructors).

    • onMethodExit

      protected void onMethodExit(int opcode)
      Generates the "after" advice for the visited method. The default implementation of this method does nothing. Subclasses can use or change all the local variables, but should not change state of the stack. This method is called at the end of the method, just before return and athrow instructions. The top element on the stack contains the return value or the exception instance. For example: 
       public void onMethodExit(final int opcode) {
   if (opcode == RETURN) {
     visitInsn(ACONST_NULL);
   } else if (opcode == ARETURN || opcode == ATHROW) {
     dup();
   } else {
     if (opcode == LRETURN || opcode == DRETURN) {
       dup2();
     } else {
       dup();
     }
     box(Type.getReturnType(this.methodDesc));
   }
   visitIntInsn(SIPUSH, opcode);
   visitMethodInsn(INVOKESTATIC, owner, "onExit", "(Ljava/lang/Object;I)V");
 }

 // An actual call back method.
 public static void onExit(final Object exitValue, final int opcode) {
   ...
 }
      Parameters:
      opcode - one of Opcodes.RETURN, Opcodes.IRETURN, Opcodes.FRETURN, Opcodes.ARETURN, Opcodes.LRETURN, Opcodes.DRETURN or Opcodes.ATHROW.