Magic Development with Aspects (Big Android BBQ Europe 2016)

Transcript

1. Magic development with Aspects Initiation to Aspect Oriented Programming Big Android BBQ Europe 2016
2. About... Xavier F. Gouchet Android Architect Jenkins/Sonar Admin Bad Puns Advocate @xgouchet on Github, StackOverflow, Twitter, …
3. “ “Let's start at the very beginning (A very good place to start)” Julie Andrews @xgouchet
4. It’s NOT ... ◎ A new programming language ◎ Something to replace OOP ◎ The solution to all your problems ! @xgouchet
5. It is a tool to ... ◎ Enhance modularity ◎ Separate cross cutting concerns ◎ Focus on business logic ◎ Reduce noise in the source code @xgouchet
6. Cross-cutting concerns ? Any concern that is not business logic and appears everywhere @xgouchet
7. Cross-cutting concerns Logging Performances Security Transactions Validation Serialisation Cache Notification Multithreading Memoization @xgouchet
8. “ “Let me tell you a story (to chill the bones)” Iron Maiden @xgouchet
9. void foo() { Log.v("Tag", "foo"); beginTransaction(); try { bar(); // ... setTransactionSuccessful(); } catch (Exception e) { reportError(e); } finally { endTransaction(); } Log.v("Tag", "foo done"); } Before / After
10. void foo() { Log.v("Tag", "foo"); beginTransaction(); try { bar(); // ... setTransactionSuccessful(); } catch (Exception e) { reportError(e); } finally { endTransaction(); } Log.v("Tag", "foo done"); } Before / After
11. void foo() { Log.v("Tag", "foo"); beginTransaction(); try { bar(); // ... setTransactionSuccessful(); } catch (Exception e) { reportError(e); } finally { endTransaction(); } Log.v("Tag", "foo done"); } Before / After
12. void foo() { Log.v("Tag", "foo"); beginTransaction(); try { bar(); // ... setTransactionSuccessful(); } catch (Exception e) { reportError(e); } finally { endTransaction(); } Log.v("Tag", "foo done"); } Before / After
13. void foo() { Log.v("Tag", "foo"); beginTransaction(); try { bar(); // ... setTransactionSuccessful(); } catch (Exception e) { reportError(e); } finally { endTransaction(); } Log.v("Tag", "foo done"); } Before / After
14. void foo() { Log.v("Tag", "foo"); beginTransaction(); try { bar(); // ... setTransactionSuccessful(); } catch (Exception e) { reportError(e); } finally { endTransaction(); } Log.v("Tag", "foo done"); } Before / After
15. @Trace @SafeTransaction void foo() { bar(); // ... } Before / After
16. “ “I've been browsing… (... inspectin’)” Weird Al Yankovic @xgouchet
17. input[type=text] { font-family: monospace; } blockquote:before { content: '\201C'; font-size: 300%; font-family: serif; } #nav-home p { color: #FF4630; cursor: pointer; } .contact img:hover { border: 1px #004080; } CSS + HTML
18. CSS Attributes Changes in appearance applied to … Elements Nodes in the source code , defined by … Selectors Rules and patterns @xgouchet
19. “ “If you know how to use CSS, Then you know how to use AOP” …me @xgouchet
20. Pointcuts Rules and patterns JoinPoints Positions in the source code , defined by … Advices Changes in behavior applied to … Aspects @xgouchet
21. Advice New behavior (=code) @xgouchet
22. JoinPoint Almost every selectable step in bytecode execution @xgouchet
23. Pointcuts Description of a (list of) joinpoints where an advice should be applied @xgouchet
24. “ “You can knit a sweater by the fireside” The Beatles @xgouchet
25. Bytecode weaving AspectJ @xgouchet
26. Code Weaving @xgouchet
27. “ “It's time to get our hands dirty” Natalie Grant @xgouchet
29. “ “It’s a kind of magic” Queen @xgouchet
30. Wizardry or Witchcraft @Aspect public class PreventNPEAspect { @Pointcut("within(com.example.model.*)") public void withinModelClass() {} @Around("withinModelClass() && execution(* *(..))") public void advice(ProceeJoinPoint jp) { Object[] args = jp.getArgs(); for (int i = 0; i < args.length; i++) { if (args[i] == null) { args[i] = ""; } } jp.proceed(args); } }
31. Wizardry or Witchcraft @Aspect public class PreventNPEAspect { @Around("execution(@PreventStringNPE * *(..))") public void advice(ProceeJoinPoint jp) { Object[] args = jp.getArgs(); for (int i = 0; i < args.length; i++) { if (args[i] == null) { args[i] = ""; } } jp.proceed(args); } }
32. “ “I wanna find some answers I wanna ask for some help ” Bruce Springsteen @xgouchet
33. FAQ ◎ What about stack traces ? Caused by: java.lang.RuntimeException at com.sample.aspectMyAspect.myAdvice(MyAspect.java:666) at com.app.model.Foo.bar(Foo.java:69) at com.app.model.Foo.<init>(Foo.java:42) at java.lang.Class.newInstance(Native Method) <9 more> ◎ What about breakpoints ? Stepping through your code is ok ◎ What about proguard ? Obfuscation performed after weaving @xgouchet
34. “ “Forever in debt to your priceless advice” Nirvana @xgouchet
35. Bad practices and code smells ◎ Pokemon (gotta catch’em all) ◎ Wizard of Oz (pay no attention to the man behind the curtain) ◎ Dr Octopus (my left tentacle doesn’t know what my right is doin’) ◎ Inception (aspects within aspects …) ◎ MacGyver (the swiss army knife @xgouchet
36. More about AspectJ… ◎ Aspects are singleton by default ◎ Inter-type declarations ◦ Change class hierarchy ◦ Add fields ◎ Declare aspects precedence ◎ Patch jar libraries @xgouchet
37. Things to remember ◎ Focus on Cross Cutting concerns ◎ If you can do it more easily with OOP don’t use AOP ◎ You can only weave code you own @xgouchet
38. Writing Aspects… ◎ Inheritance, abstracts, generics, inner classes… ◎ Unit tests ◎ Android flavors ◎ AOP is real programming @xgouchet
39. “ “There’s somethin’ we can use, so don't say no” Toni Basil @xgouchet
40. Useful links ◎ Android AspectJ plugin ◦ https://github.com/deezer/Android-Aspectj-Plugin ◎ Counsel ◦ https://github.com/deezer/Counsel ◎ AspectJ Documentation ◦ https://eclipse.org/aspectj/doc/next/progguide/ @xgouchet
41. https://speakerdeck.com/xgouchet Thanks for listening! Any question ? Deezer’s hiring http://jobs.deezer.com