1. Software Engineering Lecture 7
Vladimir Safonov,
Professor, head of laboratory
St. Petersburg University
WWW:
Язык программирования Java. Лекция 1

2. Aspect-oriented programming (AOP): Aspect
Aspect – an implementation of a crosscutting concern
Aspect – special kind of a module to be used by its weaving into other modules
Examples of aspects:
- implementation of MT safety for an existing library
- implementation of a new source language feature in a compiler
So aspects are ubiquitous in programming, but still added and located “by hand”, hence the modularity and maintenance issues
(C) Vladimir O. Safonov, 2004

3. The structure of aspect definition (V. Safonov)
Aspect name
Aspect parameters (optional) – generic aspects desirable
Aspect data
Aspect modules
Aspect actions, with their weaving rules
A separate reusable sets of weaving rules possible, to be used when weaving different aspects
(C) Vladimir O. Safonov, 2004

4. Aspects – static or dynamic?
First view on aspects: Aspect weaving is a kind of “tangled macro expansion”:
Second view: Aspect weaving is performed dynamically, at runtime
if Condition then Action
(looks like debugging breakpoints – well know for years)
Our viewpoint (V. Safonov): we take the static view but do recognize the dynamic view should be also implemented
(C) Vladimir O. Safonov, 2004

5. Aspects in AspectJ (1/2)
AspectJ: Xerox PARC (1995) -> Univ. of British Columbia, Canada (2003), designed by prof. Gregor Kichales
AspectJ – aspect-oriented extension of Java (compiler from the extended language, debugger in terms of aspects, Aspect GUI)
Pointcut – definition of a group of weaving rules ( using wildcards for entity names), - not tied to a concrete code
Join points – concrete points in concrete code to be modified in aspect weaving
Advices – actions to be performed at join points
(C) Vladimir O. Safonov, 2004

6. Aspects in AspectJ (2/2)
Aspects in AspectJ are essentially dynamic (similar to debugging-style breakpoints/debugging actions)
Introduce – weaving new definitions into a module; these definitions are visible by the aspect only (no encapsulation violation happens)
around S A -> B - AspectJ style of code modification at runtime (self-modifying code); actually, AspectJ behaves as term rewriting system.
Our viewpoint: this is a powerful tool but potentially dangerous
(C) Vladimir O. Safonov, 2004

7. Aspects in Aspect.NET (V. Safonov)
Static approach to AOP very important: it improves program readability
Aspects for .NET should be cross-language
Using custom attributes (AspectDef, AspectRef)
Syntactic sugar: a simple AOP annotations meta-language converted to AOP attributes
Aspectizing (classical term – aspect mining): turning non-AOP programs into AOP ones (coloring the aspects)
Aspect GUI
Aspect.NET site:
(C) Vladimir O. Safonov, 2004

8. Other new programming paradigms
Logic programming
Functional programming
Event-driven programming
Generic programming
Meta-programming
(C) Vladimir O. Safonov, 2004

9. Home task and references to lecture 7
- the main Web site on AOP
- the AspectJ Web site
Safonov V. O. Aspect.NET – a new approach to aspect-oriented programming. – In: “.NET Developer’s Journal”, 2003, # 4.
(C) Vladimir O. Safonov, 2004