Introduction to Aspect Oriented Programming

Introduction to AOP talk at DDD SouthWest 4.0, including examples of AOP using dynamic proxies, functional programming, dynamic language and PostSharp.

Transcript

1. Introduction to Yan Cui Aspect Oriented Programming by theburningmonk.com @theburningmonk
2. Server-side Developer @
4. • Overview  Cross-Cutting Concerns  AOP  What’s in it for you • AOP  Terminologies  AOP and OOP  Solutions • Q&A
5. CROSS-CUTTING CONCERNS the PROBLEM...
6. Image by Mike Rohde Cross-Cutting Concerns
7. • Cuts across multiple abstractions • Difficult to decompose • High-coupling • Boilerplate code
8. • Code tangling and scattering  Poor traceability  Lower productivity  Less code reuse  Harder refactoring
9. ASPECT-ORIENTED PROGRAMMING the SOLUTION...
10. “AOP is a programming paradigm which aims to increase modularity by allowing the separation of cross-cutting concerns” - wikipedia
12. Image by Mike Rohde AOP
14. • Centralize concerns implementation • Intercept method calls • Inject new behaviour • More reusable code • Cleaner code
15. What’s in it for YOU?
16. • Write less code • Read less code • More concise and easy to understand • More maintainable
17. • Fewer code = • Less boilerplate code • More interesting work • Increased attention • More PRODUCTIVITY! FEWER DEFECTS!
18. AOP dive a little deeper into...
19. • Join Point  Place where behaviour can be added  start/end of method  property getter/setter  ...
20. • Advice  Code that’s injected at join points  Logging  Validation  ...
21. • Point cut  Join points where advice should be applied
22. • Aspect  Container holding point cuts and advice  Aspect is to AOP what class is to OOP
23. • Weaving  Combines advices with point cuts
24. • AOP is complementary to OOP • AOP targets a specific problem • Code modularization  OOP – Real world objects  AOP – Functionalities
25. • Help you S.O.L.I.Dify your code  Single responsibility  Open/close
26. • You can do AOP via:  Dynamic Proxies  Functional Programming  Code Generation  Dynamic Languages  Static Weaving
27. DYNAMIC PROXIES AOP via...
28. • IoC framesworks  Castle  Spring.Net • Dynamic interceptors
29. Image by Mike Rohde Dynamic Proxies
31. • Advantages  Can use existing DI framework  Built-in aspects (logging, etc.)  Aspects can be configured after build
32. • Disadvantages  Significant change to base code required to adapt  Limited AOP features  Do not work on static, non-public methods  Do not work on fields, properties, or events  Higher run-time overhead  No build-time verification  Objects must be instantiated using the container
33. Class, is AOP the same as Dependency Injection? NOOOO Sir!!
34. FUNCTIONAL PROGRAMMING AOP via...
35. Image by Mike Rohde Functional Programming
37. • Advantages  No external dependencies
38. • Disadvantages  Requires modification to every function  No support for matching rules  Manual aspect composition
39. CODE GENERATION AOP via...
40. • T4, CodeSmith tools
41. • Advantages  Easy to generate complex source code
42. • Disadvantages  Input is usually XML  Cannot inject new behaviour to existing code
43. DYNAMIC LANGUAGES AOP via...
44. Image by Mike Rohde Dynamic Languages
45. • Advantages  Meta-programming is easy
46. • Disadvantages  Switch to a dynamic language can be hard  No (limited) Visual Studio tooling
47. STATIC WEAVING AOP via...
48. • PostSharp, AspectJ • Uses low-level MSIL transformation • Compile time
49. Aspect Decomposition Aspects Core program Aspect Recomposition Requirements Final System
50. Image by Mike Rohde PostSharp
51. • Advantages  Most complete support of AOP features  Aspect usage is verified at build time  Better runtime performance
52. • Disadvantages  Increased build time  New to many developers
53. PostSharp Examples • Auto-implement INotifyPropertyChanged • Undo/Redo • Thread dispatching • Transaction handling • Performance Monitoring
54. • Performance Monitoring  Method execution time  Method execution count  Error count
55. Record exec time Publish to Amazon CloudWatch
57. • Amazon CloudWatch  Cheap to run  Supports alarms and notifications  Visualization tool
58. • http://bit.ly/KRDdgr
59. Thank You! @theburningmonk theburningmonk.com