This document discusses aspect-oriented programming (AOP) and how it can be used to clean up code. It begins with an introduction to AOP and what aspects are, which are pieces of cross-cutting functionality used across multiple parts of a system. Examples are given of common cross-cutting concerns like logging and caching. The document then demonstrates how to refactor code to use aspects through examples and discusses benefits like improved encapsulation and reuse. It also covers how to test aspects by testing pointcuts and advice functionality.

1. Aspect-Oriented
Programming
How can aspects clean your code?
Basia Fusińska

2. About me
Aspect-Oriented ProgrammingHow can aspects clean your code? 2
@basiafusinska
Programmer
Architect
Coach
Manager
Teacher
Trainer

3. Agenda
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❖ What the hell...are aspects?
❖ Some examples of AOP
❖ Demo 1: refactor your way to aspects
❖ Every-day aspects
❖ Demo 2: some not-so-obvious aspects
❖ How to test aspects
❖ Demo 3: testing in practice
❖ Q & A
How can aspects clean your code?Aspect-Oriented Programming

4. Some history
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❖ Gregor Kiczales (1997), Xerox PARC
❖ OOP is unable to solve some common problems
❖ Aspects encapsulate cross-cutting concerns and make them easier to reuse
How can aspects clean your code?Aspect-Oriented Programming

5. Cross cutting concerns
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❖ Cross-cutting concerns are scattered throughout the code
❖ Code becomes difficult to develop and modify
❖ Code breaks the Single Responsibility Principle
How can aspects clean your code?Aspect-Oriented Programming

6. Cross-cutting concerns are everywhere!
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❖ Logging
❖ Validation
❖ Persistence
❖ Caching
❖ Synchronization
❖ Transactions
❖ Exception handling
❖ Authentication
❖ Authorization
❖ ...
How can aspects clean your code?Aspect-Oriented Programming

7. What the heck are aspects?
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❖ Purpose: cross-cutting concerns – pieces of functionality used across multiple
parts of a system
❖ Job: the advice – code that performs cross-cutting concern
❖ Map: pointcut – set of joinpoints
❖ How: weaving
How can aspects clean your code?Aspect-Oriented Programming

8. How it works?
6How can aspects clean your code?Aspect-Oriented Programming

9. Types of advices?
6How can aspects clean your code?Aspect-Oriented Programming
❖ Entry
❖ Exit
❖ Exception
❖ Success
❖ Around
❖ Method boundaries vs method interceptions

10. Some benefits of AOP
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❖ Code is cleaner
❖ DRY (Don’t Repeat Yourself): promotes code reuse
❖ Better encapsulation
How can aspects clean your code?Aspect-Oriented Programming

11. 9How can aspects clean your code?Aspect-Oriented Programming
Demonstration #1
Refactor your way to aspects

12. You’ve been using AOP without knowing it
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❖ IHttpModule - requests boundary aspects
❖ IActionFilter - code run before and after the action execution
❖ ASP.Net MVC Authentication - AuthorizeAttribute
❖ Actions per request (Session Open/Close, ORM changes saving)
How can aspects clean your code?Aspect-Oriented Programming

13. 11How can aspects clean your code?Aspect-Oriented Programming
Demonstration #2
Some not-so-obvious aspects

14. Testing aspects
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❖ Testing the pointcut – testing if aspects were used in correct places
❖ Testing the advice – testing if the aspects are doing what they are supposed
to do
How can aspects clean your code?Aspect-Oriented Programming

15. 13How can aspects clean your code?Aspect-Oriented Programming
Demonstration #3
Testing aspects

16. Thank you :)
Any questions?
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