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<h2>Additional Crosscutting Comparison functionality</h2>
The following new features are available in development builds or later, for Eclipse 3.2M5a.
A <b>Propagate Up</b> toggle button has been added to the Crosscutting
Comparison view. The sources and targets of relationships shown in the view
can be methods, types, and join points within methods, such as calls to
other methods and catch blocks. Pressing the toggle button increases
the level of granularity by replacing these sub-method elements with their
enclosing method. This means that a comparison between two locations
within the same method would normally show as a difference, but with the
toggle selected, they would be considered the same.
The original crosscutting comparison functionality allows comparison
between two projects (or more usually two versions of the same project).
It is now possible to compare two elements within the same project. These
elements can be either advice statements or declare error/warning statements.
For example, to see whether two advice statements affect the same
locations, select them both in the outline view (or package explorer) and select
<b>Comparing Crosscutting With &gt; Each Other</b> from the context-menu.
<img src="arv1.png" width="425" height="354"
alt="Screenshot showing the compare menu">
The Crosscutting Comparison view will then show the differences between
the locations affected. One use of this would be when refactoring a
pointcut from one which lists the join points to match individually, to
one which attempts to match the same join points but with a more robust
property-based pointcut.
<img src="arv2.png" width="612" height="162"
alt="Screenshot showing the results of comparing two advice elements">
You can also compare two declare error/warning statements, or
compare one declare statement with an advice statement. This second
combination can be particularly useful when refactoring code to
use aspects. You might first use a declare warning statement to identify
behaviour that is going to be handled by an aspect, such as certain
calls to a method. You then write some advice to capture that policy,
by advising the relevant methods. But you need to check that the advice is
accurate, in that it affects the same locations identified by the declare
warning. Such a comparison might look like this:
<img src="arv3.png" width="612" height="162"
alt="Screenshot showing the results of comparing declare warning with advice">
On its own this is not that useful (particularly when the number of advised
locations is large), because the declare warning targets
specific method calls, but the advice targets the execution of methods,
so they all appear as differences in the comparison. This is where the
<b>Propagate Up</b> button comes in! By selecting this the granularity
of comparison is raised to the level of enclosing methods. This makes
the significant difference between the two elements clear:
<img src="arv4.png" width="612" height="162"
alt="Screenshot showing the results after propagating up to enclosing methods">
This shows that the declare warning affects a method (in this case it is
a method call within that method) which is not also affected by the after
advice. Naturally comparisons like this are most useful with large projects,
where the crosscutting is more wide-spread.
<b>Note:</b> We are very grateful to Charles Zhang, Irum Godil,
and Arno Jacobsen of the Middleware Systems Research Group at the University
of Toronto for contributing this functionality, as part of their
research into "Aspect Refactoring Verification" sponsored by the IBM
CAS fellowship.
Note that the crosscutting comparison view is not available for
AJDT versions 1.6 and later.