Re: [aspectj-dev] Regular expressions in pointcut expressions

[Dean Wampler <dean@xxxxxxxxxxxxxxxxxxxxx>]

Alexandre Vasseur wrote:

> ...
> Perhaps you can reformulate, since it sounds a very bad idea to write
> something like "set(...) && call(...)" since obviously there won't be
> any match for that as those are 2 different joinpoint kind.
>
>  
Right. I skipped over some details, but basically the intent is to match 
the 'set' join points where a corresponding method exists (or in 
general, some corresponding condition is met). So, it would be more like 
this:

set (* \(*\).\(*\)) && if (exists (* $2.prefix$3(..)))

or something like that. Note that even without the regular expression 
stuff, it would nice to have "exists":

set (private Foo.name) && if (exists (* Foo.prefixname(..)))

(Perhaps the "if" is redundant...)

Maybe it would also help to provide a few more details about why this is 
interesting for my Contract4J experiments. Currently, the tool has you 
define "design by contract" (DbC) tests using expressions in strings 
inside special-purpose annotations. E.g.,

@Pre ("n != null")
public void setName (String n) { this.name = n; }

Which defines a "precondition" test that "it's illegal to call setName() 
with a null argument."  Currently, rather than embed a runtime 
expression interpreter, a precompilation step is done (with Sun's APT - 
annotation processing tool) that generates aspects to implement the 
tests. So, the string expression gets converted to code, which is then 
compiled during the compilation step.

One approach to eliminating the precompilation is to introduce a 
JavaBeans-like convention where DbC tests have the same signature as the 
methods they advise with a special prefix:

public void setName (String n) { this.name = n; }
public boolean preSetName (String n) { return n != null; } 

For an attribute, I could define an invariant test that must always be 
true after any change and before any read:

private String name;
public boolean invarName () { return this.name != null; }

So, I would like to write aspects that find these occurrances of  DbC 
tests and their corresponding methods or fields and only advise the 
methods or fields with before, after, or around advice (as appropriate) 
to invoke the test methods.

dean