From Legacy to Hexagonal (Codemotion Madrid 2014)

Transcript

1. From Legacy to Hexagonal (An Unexpected Android Journey) Rubén Serrano

   @Akelael Lead Android Developer @RedboothHQ José Manuel Pereira @JMPergar Android Software Engineer @RedboothHQ

2. Agenda 1. From Legacy Code 2. Towards Hexagonal Architecture 3.

   To infinity, and beyond!

3. 1. From Legacy Code

4. Meet the team

5. None
6. None

7. One dev from a contractor

8. One dev from a contractor + one senior iOS dev

9. One dev from a contractor + one senior iOS dev

10. One dev from a contractor + one senior iOS dev

    + one junior iOS dev

11. One dev from a contractor + one senior iOS dev

    + one junior iOS dev

12. A different Android dev One dev from a contractor +

    one senior iOS dev + one junior iOS dev

13. A different Android dev One dev from a contractor +

    one senior iOS dev + one junior iOS dev + one confused Android team

14. Meet the code

15. None

16. Meet the problem

17. 1. We have a huge technical debt

18. 1. We have a huge technical debt

19. HUGE

20. None

21. 1. We have huge technical debt 2. We can’t stop

    developing new features

22. 1. We have huge technical debt 2. We can’t stop

    developing new features 3. We can’t remove debt at this point and we shouldn’t add any more

23. 2. Towards Hexagonal

24. Working with legacy code

25. Read this book

26. What have we learnt from pizza?

27. You just don’t eat the whole pizza at once

28. 1. Slice the big methods into small meaningful methods

29. 1. Slice the big methods into small meaningful methods 2.

    Identify different responsibilities and move them to other classes

30. 1. Slice the big methods into small meaningful methods 2.

    Identify different responsibilities and move them to other classes 3. Use less coupled framework components (or no components at all)

31. Model View Presenter

32. In theory

33. View Presenter Model

34. Notifies events View Presenter Model

35. Requests data View Presenter Model

36. Serves data View Presenter Model

37. Change data representation View Presenter Model

38. Tells how to draw View Presenter Model

39. Layout + Activity/ Fragment Presenter Data + Business logic

40. In code (Original code…) http://goo.gl/z5Xn2J

41. listAdapter =
 new SimpleCursorAdapter(getActivity(),
 android.R.layout.simple_list_item_1,
 null,
 new String[]{FakeDatabase.COLUMN_NAME},
 new int[]{android.R.id.text1},


    0);
 listView.setAdapter(listAdapter); MainFragment

42. 
 getLoaderManager().initLoader(0, null, new LoaderManager.LoaderCallbacks<Cursor>() {
 @Override
 public Loader<Cursor> onCreateLoader(int

    id, Bundle args) {
 return new CursorLoader(getActivity(), MainContentProvider.URI, null, null, null, null);
 }
 
 @Override
 public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
 listAdapter.swapCursor(data);
 }
 
 @Override
 public void onLoaderReset(Loader<Cursor> loader) {
 listAdapter.swapCursor(null);
 }
 }); MainFragment

43. In Code (… to MVP) http://goo.gl/Retvli

44. MainView & MainModel public interface MainView {
 public void swaplListData(Cursor

    cursor);
 } public interface MainModel {
 public void setPresenter(MainPresenter presenter);
 public void startLoadingData(Context context);
 }

45. MainFragment public class MainFragment extends Fragment implements MainView {
 //...


    
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 presenter = PresenterFactory.getMainPresenter(this);
 } @Override
 public void onActivityCreated(Bundle savedInstanceState) {
 //...
 presenter.notifyOnCreate(getActivity());
 } @Override
 public void swaplListData(Cursor cursor) {
 listAdapter.swapCursor(cursor);
 }

46. MainPresenter public class MainPresenter {
 private MainView mainView;
 private MainModel

    mainModel;
 
 //...
 
 public void notifyOnCreate(Context context) {
 mainModel.startLoadingData(context);
 }
 
 public void notifiyLoadedDataAvailable(Cursor cursor) {
 mainView.swaplListData(cursor);
 }
 }

47. PresenterFactory public class PresenterFactory {
 public static MainPresenter getMainPresenter(MainView view)

    {
 MainModel model = new MainCursorModel();
 return MainPresenter.newInstance(view, model);
 }
 }

48. MainCursorModel public class MainCursorModel implements MainModel {
 //... 
 @Override


    public void startLoadingData(Context context) {
 new LoadDataAsyncTask().execute(context);
 }
 
 private class LoadDataAsyncTask extends AsyncTask<Context, Void, Cursor > {
 //... 
 @Override
 protected void onPostExecute(Cursor result) {
 super.onPostExecute(result);
 presenter.notifiyLoadedDataAvailable(result);
 }
 }
 }

49. Pros & Cons View decoupled from model Cleaner code and

    smaller fragment/activities View and model not really decoupled (cursor) All the components use the framework

50. Hexagonal Architecture

51. In theory

52. Layout + Activity/ Fragment Presenter Data + Business logic

53. Layout + Activity/ Fragment Data domain Business logic

54. Layout + Activity/ Fragment Database Business logic Network Sensors

55. Sensors Network Database Layout + Activity/ Fragment Business logic

56. Business logic Sensors Network Database Layout + Activity/ Fragment

57. Business logic Port Port Port Port Sensors Network Database Layout

    + Activity/ Fragment

58. Sensors Network Database Layout + Activity/ Fragment Adapter Adapter Adapter

    Adapter Business logic Port Port Port Port

59. Sensors Network Database Layout + Activity/ Fragment Adapter Adapter Adapter

    Adapter Business logic Port Port Port Port

60. Sensors Network Database Layout + Activity/ Fragment Boundary Boundary Boundary

    Boundary Business logic Port Port Port Port

61. Module Core Module App Module App Module App Module App

    Core Core Core Core App App App App

62. In code (Hexagonal) http://goo.gl/lIyH0o

63. MainFragment public class MainFragment extends Fragment {
 //...
 private MainFragmentBoundary

    viewBoundary;
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 //...
 viewBoundary = MainFragmentBoundary.newInstance(this);
 }
 
 @Override
 public void onActivityCreated(Bundle savedInstanceState) {
 //...
 viewBoundary.notifyOnCreate();
 }

64. MainFragment public void setListAdapter() {
 listAdapter = new ArrayAdapter<String>(getActivity(),
 android.R.layout.simple_list_item_1,


    android.R.id.text1,
 new ArrayList<String>(0));
 listView.setAdapter(listAdapter);
 }
 
 public void swapList(List<String> names) {
 listAdapter.clear();
 listAdapter.addAll(names);
 }

65. MainFragmentBoundary public class MainFragmentBoundary implements MainViewPort {
 private MainFragment mainFragment;


    private MainLogic logic;
 
 //...
 public void notifyOnCreate() {
 logic.notifyOnCreate();
 } 
 @Override
 public void swaplListData(List<String> names) {
 mainFragment.swapList(names);
 }

66. MainModelBoundary public class MainModelBoundary implements MainModelPort {
 private MainLogic logic;


    private MainRepository repository;
 //...
 
 @Override
 public void startLoadingData() {
 repository.startLoadingData(new MainRepository.OnDataLoadedListener() {
 @Override
 public void onDataLodaded(Cursor cursor) {
 notifyDataLoaded(cursor);
 }
 });
 }
 
 private void notifyDataLoaded(Cursor cursor) {
 List<String> names = mapCursorToList(cursor);
 logic.notifiyLoadedDataAvailable(names);
 }

67. MainModelBoundary private List<String> mapCursorToList(Cursor cursor) {
 List<String> names = new

    ArrayList<String>();
 int nameColumnIndex = cursor.getColumnIndex(FakeDatabase.COLUMN_NAME);
 while (cursor.moveToNext()) {
 String name = cursor.getString(nameColumnIndex);
 names.add(name);
 }
 return names;
 }

68. Pros & Cons Logic is not going to be affected

    by framework changes Logic is pure Java: easier to test Less changes when replacing a plugin Easier for 2 devs to work on the same feature More complex architecture Need to map each POJO for each layer What happens when the plugins need to cooperate?

69. 3. To infinity, and beyond!

70. One plugin, N commands

71. Sensors Network Database Layout + Activity/ Fragment Boundary Boundary Boundary

    Boundary Business logic Port Port Port Port

72. Model Plugin Layout + Activity/ Fragment Boundary Boundary Business logic

    Port Port

73. Create task Send chat message Update note Request projects Business

    logic Port Model Plugin Boundary

74. Asynchrony?

75. Create task Send chat message Update note Request projects Business

    logic Port Model Plugin Boundary

76. We don’t like: callback’s hell + AsyncTasks

77. We don’t like: callback’s hell + AsyncTasks We don’t mind

    (but could be a problem): only commands in separate threads

78. We don’t like: callback’s hell + AsyncTasks We don’t mind

    (but could be a problem): only commands in separate threads We would love: RxJava

79. Use cases

80. Model Plugin Layout + Activity/ Fragment Boundary Boundary Business logic

    Port Port

81. Model Plugin Layout + Activity/ Fragment Presenter Use Case Model

    Plugin Use Case Repository Model Plugin Use Case

82. Conclusions photo by Daniel Sancho

83. When? • If you expect 2+ devs working on the

    same feature • Unless you are sure the app is going to die in a near future • You know for sure you will change your plugins

84. How? 1. Simple refactors 2. Model View Presenter 3. Hexagonal

85. How? 1. Simple refactors 2. Model View Presenter 3. Hexagonal

    4. Clean Architecture

86. Thank you!

87. Questions?