This document discusses different patterns for handling auto-generated code in projects. It compares the Butter Knife and Dagger patterns, which either hide generated codes or do not use reflection, respectively. The author recommends the Dagger pattern as it does not require developers to learn naming rules of generated classes or add complex proguard configurations. Hiding generated code can cause issues if class names change, while not using reflection avoids errors and makes the library easier to use for developers.

1. Designing
Auto Generated Codes
17 Nov 2015 Roppongi.aar #2
@kikuchy

2. • Hiroshi Kikuchi (@kikuchy)
• Belonging to , inc , Working on , inc (mixi group)
• Making Dating App for Android
• Strict review OJISAN
Who am I

3. APT made our work
reduced!!
So, you use APT,
and be happy!!
＼＼٩( 'ω' )‫و‬ //／／

4. … I was going to talk about
like that, but

7. Oh, you are already using
APT.

8. fin.

9. ＼(^o^)／

10. So, I ll talk about

11. Designing
Auto Generated Codes

12. What is the best way to use
Generated Code in our project?
Please consider and discuss.

13. The Problem
Make Us Wakeful

14. Case 1 (/2)

15. If you make an awesome library
hiding generated codes…
// Fields
@ExecuteSomething
String foo;
// Executor class “ThisClass$$Executor” is
generated.
// My library loads executor class automatically!
AwesomeLibrary.execute(this);

16. Alice changes Naming Rule
of Generated Class.
ex) (ClassName)$$Executor -> (ClassName)$$Doer

17. proguard-rules.pro ????

18. < Hey, I obfuscated your code!
Proguard
@ Production Build

22. Case 2 (/2)

23. If you make awesome proguard-safe library…
// Fields
@ExecuteSomething
String foo;
// Executor class “ThisClassExecutor” is
generated.
// There are no reflection, no
ClassNotFoundException!!
new ThisClassExecutor().execute(this);

24. Bob often asks you
What s the name of Generated Classes and methods and constructor arguments and
interfaces will use in Generated Code blablabla…

25. Why ask me repeatedly ?
Why I have to remember
invisible codes?
Bob
<
https://www.flickr.com/photos/greeblie/2190709020/

26. / / / / ／ | / `､ i ! |i i , l
/ / // ／ | / | | | l ! i | |
`/ｰ- ､ / ／ | / | ｌ | l l ! ! i
/ ,,,,- ﾆ=ｘ- ､_ !/ |i _, +十'ｲ i ! !
''" ／ :;;r jヽ `￣ ﾘ ,, -＝､ ﾚ | / / :|
/:::::;;;;;;;:`::::::l / :;;r ヽヽ |/| / :!
|::::::::;;;;;;;;:::::::l ｌ:::;;;;;` ::| ｌ // :!
'､:_ '''' ノ l '''' ﾉ | / :|
::::::::.. ￣ ` ー ' ,' :|
:::::::::::: , ..::::::::::::..l .:| :|
:::::::::: :::::::::::::::::::| :| :| Mmmm…
::::::::::::::: l .:| l :|
/ :| :ｌ :|
, ' :::| :| :|
` 、 ⊂ﾆ＝＝ー‐- , ｲ ::::| :| :|

27. hiding generated codes
no reflection
vs

28. Butter Knife pattern
Dagger2 pattern
vs

29. Compare patterns
Butter Knife pattern
(hiding generated codes)
Dagger2 pattern
(no reflection)
How to load generated
codes
Library dose everything Developers have to import
Proguard configuration is needed not needed
Developers have to learn only usage of library
+ generated class naming
rules
Type-Safe No Yes

30. Which we should adopt?

31. case by case

32. My Recommend:
Dagger2 pattern

33. Don’t forget
proguard conf?
Start
↓
Like beautiful
API?
Is not solidity
app necessary?
→ →
Yes
No↓
“Dagger2” pattern
→
No
Yes
↓ No↓
“Dagger2” pattern “Dagger2” pattern
“Butter
Knife”
pattern
Yes

34. No proguard,
and save the team

35. https://www.flickr.com/photos/katrinasagemuller/3751402009/

36. Appendix 1:
Auto code generation patterns

37. • Java Annotated Source Codes
• Using APT.
• ex) Dagger2, ButterKinfe, JsonPullParser, etc…
• Externals
• Gradle Task (depends on compileJava task)
• ex ) R.java, genum (← I m developing now!!!!!!!!!!!)
Source of Source Codes

38. Generated Class Depends on…
• Only Interface
• MyOwnInterface instance = new GeneratedClass();
• ex) Dagger2, (Retrofit)
• Library Classes
• LibrarySuppliedBase instance = new GeneratedClass();
• ex) Shillelagh, etc…
• Nope ¦¦ Unknown
• (Generated classes are hidden.)
• ex) ButterKnife, IntentBuilder, DeepLinkDispatch

39. Appendix 2:
Episode

40. POJO
↓
Map<String, String>

42. https://www.flickr.com/photos/yoshimov/10256644/

43. public class UserSearchRequest {
public EnumSet<UserKind> kind;
public String freeWord;
public int ageMax;
…
}

44. @ToQueryMap
public class UserSearchRequest {
@QueryParam(name = “kind”,
adapter = UserKindAdapter.class)
public EnumSet<UserKind> kind;
@QueryParam(name = “free_word”,
adapter = StringAdapter.class)
public String freeWord;
@QueryParam(name = “age_max”,
adapter = IntAdapter.class)
public int ageMax;
…

45. public final class UserSearchRequestSerializer {
public Map<String, String>
serialize(UserSearchRequest request) {
Map<String, String> map = new Map<>();
map.put(“kind”,
userKindAdapter.adapt(request.kind));
map.put(“free_word”,
stringAdapter.adapt(request.freeWord));
map.put(“age_max”,
intAdapter.adapt(request.ageMax));
…
return map;
}
GENERATED

46. Yheaaaaaaaa
＼＼٩( 'ω' )‫و‬ //／／

47. Thank you for listening!

48. Question?

49. @kikuchy