[aspectj-users] Re: Exception handling framework

[mmonteiro@xxxxxxxxxxxxxxxxx]

> I do have one remaining problem: every method in the application that
> could throw an exception should have a "throws ...Exception" in its
> declaration, or there should be a try-catch block. The catch should than
> be left empty, as the handling is done by the aspect. I do not see any
> sollution to this problem.

The idea of a exception handling framework looks a good one to me. The issue 
of throws clauses and checked exceptions versus AOP has also been troubling 
me for some time. 

There is some merit in the motivation behind checked exceptions - to ensure 
program robustness and reliability in the presence of unpredictable 
occurrences from the environment and other software components. The problem 
is that Java's mechanism of tackling this enforces code tangling, exactly 
what AOP is meant to avoid. 

I think there is a certain tension between checked exceptions and AOP. 
Aspects have the potential to modularise the issuing / handling of 
exceptions just like any other crosscutting concern. It's just that the 
"throws Exception" rule keeps getting in the way. I find it a bit funny that 
AOP's most widely used language includes a mechanism that enforces a 
crosscutting concern into its code. 

IMHO the AspectJ team should one of these days tackle this problem. The ajc 
compiler could stop generating error messages due to missing try-catch 
blocks. ajc could even provide a switch to re-activate the enforced 
try-catch (perhaps for mission-critical software), just like javac does with 
the assert statement. After all, AspectJ already enables several things that 
are forbidden by straight Java - privileged aspects are one good example.
Perhaps AspectJ could provide something along these lines in order to avoid 
all those try-catch blocks. 

--
Miguel J. T. Pessoa Monteiro
Ph.D. student Minho University, Portugal
eMail: mmonteiro@xxxxxxxxxxxx
URL: http://gec.di.uminho.pt/mpm/