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:
org.objectweb.asm.Opcodes
public abstract class AdviceAdapter extends GeneratorAdapter implements org.objectweb.asm.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, org.objectweb.asm.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()
      Overrides:
      visitCode in class org.objectweb.asm.MethodVisitor

    • visitLabel

      public void visitLabel(org.objectweb.asm.Label label)
      Overrides:
      visitLabel in class org.objectweb.asm.MethodVisitor

    • visitFrame

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

    • visitInsn

      public void visitInsn(int opcode)
      Overrides:
      visitInsn in class org.objectweb.asm.MethodVisitor

    • visitVarInsn

      public void visitVarInsn(int opcode, int varIndex)
      Overrides:
      visitVarInsn in class LocalVariablesSorter

    • visitFieldInsn

      public void visitFieldInsn(int opcode, String owner, String name, String descriptor)
      Overrides:
      visitFieldInsn in class org.objectweb.asm.MethodVisitor

    • visitIntInsn

      public void visitIntInsn(int opcode, int operand)
      Overrides:
      visitIntInsn in class org.objectweb.asm.MethodVisitor

    • visitLdcInsn

      public void visitLdcInsn(Object value)
      Overrides:
      visitLdcInsn in class org.objectweb.asm.MethodVisitor

    • visitMultiANewArrayInsn

      public void visitMultiANewArrayInsn(String descriptor, int numDimensions)
      Overrides:
      visitMultiANewArrayInsn in class org.objectweb.asm.MethodVisitor

    • visitTypeInsn

      public void visitTypeInsn(int opcode, String type)
      Overrides:
      visitTypeInsn in class org.objectweb.asm.MethodVisitor

    • visitMethodInsn

      public void visitMethodInsn(int opcodeAndSource, String owner, String name, String descriptor, boolean isInterface)
      Overrides:
      visitMethodInsn in class org.objectweb.asm.MethodVisitor

    • visitInvokeDynamicInsn

      public void visitInvokeDynamicInsn(String name, String descriptor, org.objectweb.asm.Handle bootstrapMethodHandle, Object... bootstrapMethodArguments)
      Overrides:
      visitInvokeDynamicInsn in class org.objectweb.asm.MethodVisitor

    • visitJumpInsn

      public void visitJumpInsn(int opcode, org.objectweb.asm.Label label)
      Overrides:
      visitJumpInsn in class org.objectweb.asm.MethodVisitor

    • visitLookupSwitchInsn

      public void visitLookupSwitchInsn(org.objectweb.asm.Label dflt, int[] keys, org.objectweb.asm.Label[] labels)
      Overrides:
      visitLookupSwitchInsn in class org.objectweb.asm.MethodVisitor

    • visitTableSwitchInsn

      public void visitTableSwitchInsn(int min, int max, org.objectweb.asm.Label dflt, org.objectweb.asm.Label... labels)
      Overrides:
      visitTableSwitchInsn in class org.objectweb.asm.MethodVisitor

    • visitTryCatchBlock

      public void visitTryCatchBlock(org.objectweb.asm.Label start, org.objectweb.asm.Label end, org.objectweb.asm.Label handler, String type)
      Overrides:
      visitTryCatchBlock in class org.objectweb.asm.MethodVisitor

    • 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.