Re: [aspectj-dev] type pattern "+" for declaring class

["Wes Isberg" <wes@xxxxxxxxxxxxxx>]

> without "+" a type pattern specifies the exact type without sub types. 

true

> I expected that the pointcut only 
> matches at point (1). But it matches at point (1) and point (2)

Briefly:
Matching both is correct, since both have that signature.
An execution join point can have more than one signature.

More detail:
Shape declares the join point signature moveBy(int, int),
regardless of whether Point also declares it.  This is 
specified in the programming guide semantics appendix 
section on matching:
------------------------------
When matching method-execution join points, if the execution 
pointcut method signature specifies a declaring type, the 
pointcut will only match methods declared in that type, or 
methods that override methods declared in or inherited by that type
------------------------------

Put another way, the bytecode shadow for Point.moveBy(int,int)
has more than one signature:

  void Shape.moveBy(int, int)
  void Point.moveBy(int, int)

The AspectJ 5 developers notebook mentions the many
signatures for an execution join point signature.
  http://dev.eclipse.org/viewcvs/indextech.cgi/%7Echeckout%7E/aspectj-home/doc/ajdk15notebook/join-point-signatures.html#d0e351

This can sound funny, but it tracks what developers expect.
Most developers want to advise any implementation of a given
method.  Those who want to specify a particular lexical class
can say

  within(Shape) && execution(void Shape.moveBy(int, int))

Hope this helps!

Wes

> ------------Original Message------------
> From: Christoph Bockisch <bockisch@xxxxxxxxxxxxxxxxxxxxxxxxxx>
> To: aspectj-dev@xxxxxxxxxxx
> Date: Thu, Feb-10-2005 5:11 AM
> Subject: [aspectj-dev] type pattern "+" for declaring class
>
> In each documentation about AspectJ that I found, it is stated that 
> without "+" a type pattern specifies the exact type without sub types. 
> However this documentation is at least ambiguous for type patterns used 
> 
> for the declaring class. Look at the following example:
> 
> class Shape {
>    void moveBy(int x, int y) { (1) ... }
> }
> 
> class Point extends Shape {
>    void moveBy(int x, int y) { (2) ... }
> }
> 
> Consider the pointcut: execution(* Shape.moveBy(int, int))
> 
> After reading the documentation, I expected that the pointcut only 
> matches at point (1). But it matches at point (1) and point (2). I 
> think, given that Java provides polymorphism, this behavior is correct. 
> 
> However I think that this breaks the invariant (which is stated in the 
> documentation) that type patterns without "+" always specify the exact 
> class.
> 
> I would be happy to hear from you how the semantics for type patterns 
> with and without "+" in the declaring class are intended to be.
> 
> Thanks in advance,
> Christoph Bockisch
> 
> 
> -- 
> Dipl.-Inform. Christoph Bockisch    bockisch@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Software Technology Group           Phone:  ++49 (0) 6151-16-3608
> Darmstadt University of Technology  Fax:    ++49 (0) 6151-16-5410
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