Package org.springframework.aop.aspectj

Class AspectJAdviceParameterNameDiscoverer

java.lang.Object
org.springframework.aop.aspectj.AspectJAdviceParameterNameDiscoverer
All Implemented Interfaces:
org.springframework.core.ParameterNameDiscoverer
public class AspectJAdviceParameterNameDiscoverer extends Object implements org.springframework.core.ParameterNameDiscoverer
ParameterNameDiscoverer implementation that tries to deduce parameter names for an advice method from the pointcut expression, returning, and throwing clauses. If an unambiguous interpretation is not available, it returns null.

Algorithm Summary

If an unambiguous binding can be deduced, then it is. If the advice requirements cannot possibly be satisfied, then null is returned. By setting the raiseExceptions property to true, descriptive exceptions will be thrown instead of returning null in the case that the parameter names cannot be discovered.

Algorithm Details

This class interprets arguments in the following way:

  1. If the first parameter of the method is of type JoinPoint or ProceedingJoinPoint, it is assumed to be for passing thisJoinPoint to the advice, and the parameter name will be assigned the value "thisJoinPoint".
  2. If the first parameter of the method is of type JoinPoint.StaticPart, it is assumed to be for passing "thisJoinPointStaticPart" to the advice, and the parameter name will be assigned the value "thisJoinPointStaticPart".
  3. If a throwingName has been set, and there are no unbound arguments of type Throwable+, then an IllegalArgumentException is raised. If there is more than one unbound argument of type Throwable+, then an AspectJAdviceParameterNameDiscoverer.AmbiguousBindingException is raised. If there is exactly one unbound argument of type Throwable+, then the corresponding parameter name is assigned the value <throwingName>.
  4. If there remain unbound arguments, then the pointcut expression is examined. Let a be the number of annotation-based pointcut expressions (@annotation, @this, @target, @args, @within, @withincode) that are used in binding form. Usage in binding form has itself to be deduced: if the expression inside the pointcut is a single string literal that meets Java variable name conventions it is assumed to be a variable name. If a is zero we proceed to the next stage. If a > 1 then an AmbiguousBindingException is raised. If a == 1, and there are no unbound arguments of type Annotation+, then an IllegalArgumentException is raised. If there is exactly one such argument, then the corresponding parameter name is assigned the value from the pointcut expression.
  5. If a returningName has been set, and there are no unbound arguments then an IllegalArgumentException is raised. If there is more than one unbound argument then an AmbiguousBindingException is raised. If there is exactly one unbound argument then the corresponding parameter name is assigned the value of the returningName.
  6. If there remain unbound arguments, then the pointcut expression is examined once more for this, target, and args pointcut expressions used in the binding form (binding forms are deduced as described for the annotation based pointcuts). If there remains more than one unbound argument of a primitive type (which can only be bound in args) then an AmbiguousBindingException is raised. If there is exactly one argument of a primitive type, then if exactly one args bound variable was found, we assign the corresponding parameter name the variable name. If there were no args bound variables found an IllegalStateException is raised. If there are multiple args bound variables, an AmbiguousBindingException is raised. At this point, if there remains more than one unbound argument we raise an AmbiguousBindingException. If there are no unbound arguments remaining, we are done. If there is exactly one unbound argument remaining, and only one candidate variable name unbound from this, target, or args, it is assigned as the corresponding parameter name. If there are multiple possibilities, an AmbiguousBindingException is raised.

The behavior on raising an IllegalArgumentException or AmbiguousBindingException is configurable to allow this discoverer to be used as part of a chain-of-responsibility. By default the condition will be logged and the getParameterNames(Method) method will simply return null. If the raiseExceptions property is set to true, the conditions will be thrown as IllegalArgumentException and AmbiguousBindingException, respectively.

Since:
2.0
Author:
Adrian Colyer, Juergen Hoeller

  • Constructor Details

    • AspectJAdviceParameterNameDiscoverer

      public AspectJAdviceParameterNameDiscoverer(@Nullable String pointcutExpression)
      Create a new discoverer that attempts to discover parameter names. from the given pointcut expression.

  • Method Details

    • setRaiseExceptions

      public void setRaiseExceptions(boolean raiseExceptions)
      Indicate whether IllegalArgumentException and AspectJAdviceParameterNameDiscoverer.AmbiguousBindingException must be thrown as appropriate in the case of failing to deduce advice parameter names.
      Parameters:
      raiseExceptions - true if exceptions are to be thrown

    • setReturningName

      public void setReturningName(@Nullable String returningName)
      If afterReturning advice binds the return value, the returning variable name must be specified.
      Parameters:
      returningName - the name of the returning variable

    • setThrowingName

      public void setThrowingName(@Nullable String throwingName)
      If afterThrowing advice binds the thrown value, the throwing variable name must be specified.
      Parameters:
      throwingName - the name of the throwing variable

    • getParameterNames

      @Nullable public String[] getParameterNames(Method method)
      Deduce the parameter names for an advice method.

      See the class-level javadoc for this class for details on the algorithm used.

      Specified by:
      getParameterNames in interface org.springframework.core.ParameterNameDiscoverer
      Parameters:
      method - the target Method
      Returns:
      the parameter names

    • getParameterNames

      @Nullable public String[] getParameterNames(Constructor<?> ctor)
      An advice method can never be a constructor in Spring.
      Specified by:
      getParameterNames in interface org.springframework.core.ParameterNameDiscoverer
      Returns:
      null
      Throws:
      UnsupportedOperationException - if raiseExceptions has been set to true