[aspectj-dev] Regular expressions in pointcut expressions

[Dean Wampler <dean@xxxxxxxxxxxxxxxxxxxxx>]

I'm reworking my pet "Contract4J" project and I've discovered that 
support for some common Perl-like regular expression idioms in pointcuts 
would really help.  I would like to be able to write pointcuts that find 
a method or attribute "foo" and method "prefixFoo" (like the JavaBeans 
idiom for get/set), where foo is actually some sort of regular 
expression. For attributes, I would need something like

set (* \(*\).\(*\)) && call (* $2.prefix$3(..))

meaning "find all attempts to set an attribute in a class, save the 
attribute name in '$3' (the third group of escaped parentheses...) and 
the class name in '$2', but match join points only if there is a 
corresponding method in the same class '$2' named 'prefix$3'. (Actually, 
this doesn't convert the first letter of $3 to upper case, but ...).

I'm using escaped parentheses to distinguish between grouping constructs 
and method argument boundaries, etc. Note that something like

set (* *.*) && call (* *.prefix*(..))

would pick out sets of attributes in class "Foo" and methods like 
"Bar.prefixSomethingUnrelated(..)", which isn't helpful.

A similar expression for methods would be something like:

call (* \(*\).\(*\)(\(..\))) && call (* $2.prefix$3($4))

(Clearly there are legibility issues with the parentheses...)

Of course, the workaround is to match a larger set of join points, e.g., 
just use

set (* *.*)

and to compute the information you need using reflection, etc. (I'm 
doing this now...) Efficiency becomes an issue, though. In general, 
being able to reason inline about the matched strings would be useful 
(especially at compile time) and it would make it easier to write 
reusable aspects while avoiding combinatorial explosions of advice and 
runtime overhead.

Does this make sense? If implemented, would it work with reasonable 
performance, etc. for potentially large programs?


dean

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Dean Wampler, Ph.D.
dean at aspectprogramming.com
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http://www.contract4j.org
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