Android: Code Generation Beyond APT

Presented in May '17 Blrdroid meetup.
https://www.meetup.com/blrdroid/events/239270928

Transcript

1. Code Generation beyond APT Ragunath Jawahar
2. An Android developer walks into the bar…
3. An Android developer walks into the bar office…
5. Analytics Code MixpanelAPI mixpanel = MixpanelAPI.getInstance(this, token); try { JSONObject payload  = new JSONObject(); payload.put("Gender", "Female"); payload.put("Logged  in", false); payload.put("Source", "Twitter"); mixpanel.track("Signup", payload); } catch (JSONException exception) { Log.e("Frodo", "JsonException", exception); }
6. Analytics Code MixpanelAPI mixpanel = MixpanelAPI.getInstance(this, token); try  { JSONObject payload  =  new  JSONObject(); payload.put("Gender",  "Female"); payload.put("Logged  in",  false); payload.put("Source",  "Twitter"); mixpanel.track("Signup",  payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }
7. Analytics Code MixpanelAPI mixpanel =  MixpanelAPI.getInstance(this,  token); try  { JSONObject payload  = new JSONObject(); payload.put("Gender", "Female"); payload.put("Logged  in", false); payload.put("Source", "Twitter"); mixpanel.track("Signup",  payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }
8. Analytics Code MixpanelAPI mixpanel =  MixpanelAPI.getInstance(this,  token); try  { JSONObject payload  =  new  JSONObject(); payload.put("Gender",  "Female"); payload.put("Logged  in",  false); payload.put("Source",  "Twitter"); mixpanel.track("Signup", payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }
9. GREMLINS
12. …and only 300 more rows
13. MAY THE “BRUTE” FORCE BE WITH YOU
14. Problems •Slow •Boring •Inaccurate •Error Prone •Hard to Test •Difficult to Change •Multiple Platforms •Multiple Apps
15. Requirements • Accuracy • Accommodate Changes • Don’t Leak Cognitive Resources • Testability • Support Multiple Apps and Platforms
16. AOP
17. AOP
19. WORKFLOW – SCREEN – EVENT
20. workflow().screen().event()
23. Java Poet – Method MethodSpec mainMethod = MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC, Modifier.STATIC) .addParameter(String[].class, "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();
24. Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();
25. Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC, Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();
26. Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class, "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();
27. Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();
28. Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();
29. Java Poet – Class TypeSpec greeterClass = TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();
30. Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();
31. Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();
32. Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();
33. Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();
34. Java Poet – Compilation Unit JavaFile greeterFile = JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);
35. Java Poet – Compilation Unit JavaFile greeterFile =  JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);
36. Java Poet – Compilation Unit JavaFile greeterFile =  JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);
37. Java Poet – Compilation Unit JavaFile greeterFile =  JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);
38. Java Poet – Generated Class package in.kitecash; import java.lang.String; import java.lang.System; public class Greeter { public static void main(String[] args) { System.out.println("Hello,  World!"); } }
39. BLUEPRINT
40. ITERATE ON PAPER
41. Components •CSV Parser •Source Code Generator
42. Objective workflow().screen().event()
43. High-Level Design •Top-level Workflow classes •Inner Screen classes •Top-level Analytics class •Top-level Tracker abstract class
44. Class Diagram …  more  workflow  classes
45. Class Diagram …  more  inner  screen  classes
46. workflow().screen().event() •Methods present inside Analytics class •Workflows are generated as top-level classes •Workflows encapsulate Screen inner classes
47. workflow().screen().event() •Methods present inside Workflow classes •Screens are generated as inner classes in Workflows •Screens encapsulate event methods
48. workflow().screen().event() •Methods present inside Screen classes •May accept parameters for collecting additional data
49. Analytics •Contains  Workflow methods  that  provide   instances  of  Workflow classes •Instantiated  by  supplying  a  Tracker implementation
50. Tracker public abstract class Tracker { public  abstract  void track(String event, Map<String, String> payload); }
51. Tracker public  abstract  class  Tracker  { public  abstract  void track(String event, Map<String, String> payload); }
52. Tracker public  abstract  class  Tracker  { public  abstract  void  track(String event, Map<String,  String>  payload); }
53. Tracker public  abstract  class  Tracker  { public  abstract  void  track(String  event, Map<String, String> payload); }
54. ACCURACY
55. WRITE CODE TO GENERATE CODE
56. CHANGES
57. CSV Removals – Red Markers
58. CSV Additions – Yellow Markers
59. PRODUCTIVITY
60. Auto-Completion
61. versus this? MixpanelAPI mixpanel =  MixpanelAPI.getInstance(this,  token); try  { JSONObject payload  =  new  JSONObject(); payload.put("Gender",  "Female"); payload.put("Logged  in",  false); payload.put("Source",  "Twitter"); mixpanel.track("Signup",  payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }
62. Checklist
63. Checklist
64. Checklist
65. TESTING
66. Gradle & Dagger •Multiple Build Types •Multiple Modules and Components
67. Trackers •Logcat Tracker •Mixpanel Tracker •Dialog Tracker •Verifying Tracker
68. LogcatTracker public class LogcatTracker implements Tracker { private static final String TAG  = "LogcatTracker"; @Override public void track(String trigger, Map<String, String> payload) { Log.d(TAG, "Received  trigger:  " + trigger  +  ",  " + payload); } }
69. LogcatTracker public  class  LogcatTracker implements  Tracker  { private  static  final  String  TAG  =  "LogcatTracker"; @Override public  void  track(String  trigger,  Map<String,  String>  payload)  { Log.d(TAG, "Received  trigger:  " + trigger  +  ",  " + payload); } }
70. AlertDialogTracker public class AlertDialogTracker implements Tracker { private final Context context; public AlertDialogTracker(Context context) { this.context = context; } @Override public void track(String trigger, Map<String, String> payload) { StringBuilder messageBuilder = new StringBuilder(); //  Create  a  String  message  from  the  payload... showAlertDialog(trigger, stringBuilder.toString()); } }
71. AlertDialogTracker public  class  AlertDialogTracker implements  Tracker  { private  final  Context  context; public  AlertDialogTracker(Context  context)  { this.context =  context; } @Override public  void  track(String  trigger,  Map<String,  String>  payload)  { StringBuilder messageBuilder = new StringBuilder(); //  Create  a  String  message  from  the  payload... showAlertDialog(trigger, stringBuilder.toString()); } }
72. MixpanelTracker public class MixpanelTracker implements Tracker { private final MixpanelAPI mixpanel; public MixpanelTracker(Context context, String projectToken) { this.mixpanel = MixpanelAPI.getInstance(context, projectToken); } @Override public void track(String trigger, Map<String, String> payload) { JSONObject properties  = new JSONObject(); //  Populate  the  JSONObject from  payload... mixpanel.track(trigger, properties); } }
73. MixpanelTracker public  class  MixpanelTracker implements  Tracker  { private  final  MixpanelAPI mixpanel; public  MixpanelTracker(Context context, String projectToken)  { this.mixpanel =  MixpanelAPI.getInstance(context,  projectToken); } @Override public  void  track(String  trigger,  Map<String,  String>  payload)  { JSONObject properties  =  new  JSONObject(); //  Populate  the  JSONObject from  payload... mixpanel.track(trigger,  properties); } }
74. MixpanelTracker public  class  MixpanelTracker implements  Tracker  { private  final  MixpanelAPI mixpanel; public  MixpanelTracker(Context  context,  String  projectToken)  { this.mixpanel =  MixpanelAPI.getInstance(context,  projectToken); } @Override public  void  track(String  trigger,  Map<String,  String>  payload)  { JSONObject properties  = new JSONObject(); //  Populate  the  JSONObject from  payload... mixpanel.track(trigger, properties); } }
75. iOS + Swift
76. Difficulties •Swift •No Transpilers •No Code Generation Libraries
77. J2ObjC
78. J2ObjC Java Objective-C Swift
79. J2ObjC Java Objective-C Swift
80. J2ObjC Java Objective-C Swift
81. PEACE
82. PEACE
83. abstract  class(es) NOT interface(s)
84. J2ObjC Nuances •Runtime Library •Adds ~10 MB
85. PROCESS
86. Overview • Export spreadsheet from BI team as CSV • Check exported CSV into analytics project • Run Gradle task to generate source code from CSV • Copy generated source code into Android projects • Send generated source code to iOS team • iOS team includes transpiled source code to iOS projects
87. Gradle Task task  generateAnalyticsSource(type: JavaExec) { classpath files('../sidekick/analytics/bin/grumpy-­‐old-­‐man.jar') main  'in.kitecash.sidekick.analytics.GrumpyOldMan' }
88. Gradle Task task  generateAnalyticsSource(type:  JavaExec)  { classpath files('../sidekick/analytics/bin/grumpy-­‐old-­‐man.jar') main  'in.kitecash.sidekick.analytics.GrumpyOldMan' }
89. Gradle Task task  generateAnalyticsSource(type:  JavaExec)  { classpath files('../sidekick/analytics/bin/grumpy-­‐old-­‐man.jar') main  'in.kitecash.sidekick.analytics.GrumpyOldMan' }
90. TAKEAWAY
91. Code Generation Tips • Iterate through the design several times • Doesn’t have to be DRY • Use a prefix in generated source files • Add “Auto-Generated” comments and Javadoc • Prefer abstract classes over interfaces • Extract platform-specific code, use abstraction
92. 2 Moar Cents •Make tools work for you •Communicate with all teams that are involved, this is the key
93. ragunathjawahar GitHub / Twitter / Speakerdeck