RxJava et Java 8 Pour Sortir de l'Enfer des Callbacks [quickie]

Comment la combinaison de la librairie RxJava (programmation réactive) et des lambdas de Java 8 peuvent idéalement nous sortir de l'Enfer des Callbacks. Quickie donné à DevoxxFR 2014

1. #CallBackHell @simonbasle Sortir de l’Enfer des Callbacks RxJava + Java 8
2. #CallBackHell @simonbasle @SimonBasle @ZenikaIT @InfoQFR @bbl_fr
3. #CallBackHell @simonbasle L‘Enfer des Callbacks?
4. #CallBackHell @simonbasle L‘Enfer des Callbacks?
5. #CallBackHell @simonbasle synchrone == inefficace*
6. #CallBackHell @simonbasle nous avons besoin de code asynchrone
7. #CallBackHell @simonbasle nous avons besoin de code asynchrone réactif
8. #CallBackHell @simonbasle nous avons besoin de code asynchrone parallélisable
9. #CallBackHell @simonbasle nous avons besoin de code asynchrone composable
10. #CallBackHell @simonbasle nous avons besoin de code asynchrone lisible
11. #CallBackHell @simonbasle mais comment bien faire Asynchrone ?
12. #CallBackHell @simonbasle les Futures<T>
13. #CallBackHell @simonbasle les Futures<T> une modélisation lisible
14. #CallBackHell @simonbasle les Futures<T> peuvent bloquer (get)
15. #CallBackHell @simonbasle les Futures<T> deviennent compliquées au delà d’un niveau
16. #CallBackHell @simonbasle les Futures<T> se composent mal
17. #CallBackHell @simonbasle les Callbacks
18. #CallBackHell @simonbasle les Callbacks tout simple
19. #CallBackHell @simonbasle les Callbacks pas de blocage possible
20. #CallBackHell @simonbasle les Callbacks ne se composent pas
21. #CallBackHell @simonbasle les Callbacks deviennent vite illisibles
22. #CallBackHell @simonbasle EXEMPLE : je veux mes 10 premiers docs marqués comme favoris sous forme de json complet
23. #CallBackHell @simonbasle Pour ça je dois agréger en asynchrone : méta commentaires & auteurs description d’images
24. #CallBackHell @simonbasle DocumentService.find("userId", new Callback<List<Document>>() { public void onSuccess(List<Document> result) { final List<String> jsonList = new ArrayList<String>(10); int taken = 0; for (Document doc : result) { if (taken >= 10) break; if (!doc.isStarred()) continue; taken++; final CountDownLatch rendezVous = new CountDownLatch(3); final JsonObject jsonBuffer = new JsonObject(); jsonBuffer.appendInt("id", doc.getId()); jsonBuffer.append("text", doc.getText()); CommentService.findForDoc(doc, new Callback<List<Comment>>() { public void onSuccess(List<Comment> comments) { final JsonObject commentArray = JsonObject.createArray(); CountDownLatch userLatch = new CountDownLatch(comments.size()); for (Comment c : comments) { JsonObject cj = new JsonObject(); cj.append("content", c.getText()); cj.append("date", c.getDate()); UserService.find(c.getUserId(), new Callback<User>() { public void onSuccess(User user) { cj.append("author", user.getName()); cj.append("nickname", user.getLogin()); cj.append("email", user.getEmail()); // …
25. #CallBackHell @simonbasle // … continued commentArray.add(cj); userLatch.countDown(); } }); } userLatch.await(); jsonBuffer.addArray("comments", commentArray); rendezVous.countDown(); } }); MetaService.findForDoc(doc, new Callback<List<Meta>>() { public void onSuccess(List<Meta> metas) { jsonBuffer.addArray("meta", jsonify(metas)); rendezVous.countDown(); } }); PictureService.findAllMetas(doc.getPictures(), new Callback<List<PicMeta>>() { public void onSuccess(List<PicMeta> picMetas) { jsonBuffer.addArray("pictures", jsonify(picMetas)); rendezVous.countDown(); } }); rendezVous.await(); jsonList.add(jsonBuffer.toString()); } somethingToDo.onSuccess(jsonList); } });
26. #CallBackHell @simonbasle 2 slides en taille 10 58 lignes de code max 7 tabulations
27. #CallBackHell @simonbasle jusqu’à 3 Callbacks imbriqués 2 usages de CountDownLatch
28. #CallBackHell @simonbasle DocumentService.find("userId", new Callback<List<Document>>() { public void onSuccess(List<Document> result) { final List<String> jsonList = new ArrayList<String>(10); int taken = 0; for (Document doc : result) { if (taken >= 10) break; if (!doc.isStarred()) continue; taken++; final CountDownLatch rendezVous = new CountDownLatch(3); final JsonObject jsonBuffer = new JsonObject(); jsonBuffer.appendInt("id", doc.getId()); jsonBuffer.append("text", doc.getText()); CommentService.findForDoc(doc, new Callback<List<Comment>>() { public void onSuccess(List<Comment> comments) { final JsonObject commentArray = JsonObject.createArray(); CountDownLatch userLatch = new CountDownLatch(comments.size()); for (Comment c : comments) { JsonObject cj = new JsonObject(); cj.append("content", c.getText()); cj.append("date", c.getDate()); UserService.find(c.getUserId(), new Callback<User>() { public void onSuccess(User user) { cj.append("author", user.getName()); cj.append("nickname", user.getLogin()); cj.append("email", user.getEmail()); // … THIS
29. #CallBackHell @simonbasle IS DocumentService.find("userId", new Callback<List<Document>>() { public void onSuccess(List<Document> result) { final List<String> jsonList = new ArrayList<String>(10); int taken = 0; for (Document doc : result) { if (taken >= 10) break; if (!doc.isStarred()) continue; taken++; final CountDownLatch rendezVous = new CountDownLatch(3); final JsonObject jsonBuffer = new JsonObject(); jsonBuffer.appendInt("id", doc.getId()); jsonBuffer.append("text", doc.getText()); CommentService.findForDoc(doc, new Callback<List<Comment>>() { public void onSuccess(List<Comment> comments) { final JsonObject commentArray = JsonObject.createArray(); CountDownLatch userLatch = new CountDownLatch(comments.size()); for (Comment c : comments) { JsonObject cj = new JsonObject(); cj.append("content", c.getText()); cj.append("date", c.getDate()); UserService.find(c.getUserId(), new Callback<User>() { public void onSuccess(User user) { cj.append("author", user.getName()); cj.append("nickname", user.getLogin()); cj.append("email", user.getEmail()); // …
30. #CallBackHell @simonbasle callback DocumentService.find("userId", new Callback<List<Document>>() { public void onSuccess(List<Document> result) { final List<String> jsonList = new ArrayList<String>(10); int taken = 0; for (Document doc : result) { if (taken >= 10) break; if (!doc.isStarred()) continue; taken++; final CountDownLatch rendezVous = new CountDownLatch(3); final JsonObject jsonBuffer = new JsonObject(); jsonBuffer.appendInt("id", doc.getId()); jsonBuffer.append("text", doc.getText()); CommentService.findForDoc(doc, new Callback<List<Comment>>() { public void onSuccess(List<Comment> comments) { final JsonObject commentArray = JsonObject.createArray(); CountDownLatch userLatch = new CountDownLatch(comments.size()); for (Comment c : comments) { JsonObject cj = new JsonObject(); cj.append("content", c.getText()); cj.append("date", c.getDate()); UserService.find(c.getUserId(), new Callback<User>() { public void onSuccess(User user) { cj.append("author", user.getName()); cj.append("nickname", user.getLogin()); cj.append("email", user.getEmail()); // …
31. #CallBackHell @simonbasle HEEEELL! DocumentService.find("userId", new Callback<List<Document>>() { public void onSuccess(List<Document> result) { final List<String> jsonList = new ArrayList<String>(10); int taken = 0; for (Document doc : result) { if (taken >= 10) break; if (!doc.isStarred()) continue; taken++; final CountDownLatch rendezVous = new CountDownLatch(3); final JsonObject jsonBuffer = new JsonObject(); jsonBuffer.appendInt("id", doc.getId()); jsonBuffer.append("text", doc.getText()); CommentService.findForDoc(doc, new Callback<List<Comment>>() { public void onSuccess(List<Comment> comments) { final JsonObject commentArray = JsonObject.createArray(); CountDownLatch userLatch = new CountDownLatch(comments.size()); for (Comment c : comments) { JsonObject cj = new JsonObject(); cj.append("content", c.getText()); cj.append("date", c.getDate()); UserService.find(c.getUserId(), new Callback<User>() { public void onSuccess(User user) { cj.append("author", user.getName()); cj.append("nickname", user.getLogin()); cj.append("email", user.getEmail()); // …
32. #CallBackHell @simonbasle Wow Such Space! #CallBackHell @simonbasle DocumentService.find("userId", new Callback<List<Document>>() { public void onSuccess(List<Document> result) { final List<String> jsonList = new ArrayList<String>(10); int taken = 0; for (Document doc : result) { if (taken >= 10) break; if (!doc.isStarred()) continue; taken++; final CountDownLatch rendezVous = new CountDownLatch(3); final JsonObject jsonBuffer = new JsonObject(); jsonBuffer.appendInt("id", doc.getId()); jsonBuffer.append("text", doc.getText()); CommentService.findForDoc(doc, new Callback<List<Comment>>() { public void onSuccess(List<Comment> comments) { final JsonObject commentArray = JsonObject.createArray(); CountDownLatch userLatch = new CountDownLatch(comments.size()); for (Comment c : comments) { JsonObject cj = new JsonObject(); cj.append("content", c.getText()); cj.append("date", c.getDate()); UserService.find(c.getUserId(), new Callback<User>() { public void onSuccess(User user) { cj.append("author", user.getName()); cj.append("nickname", user.getLogin()); cj.append("email", user.getEmail()); // …
33. #CallBackHell @simonbasle RxJava
34. #CallBackHell @simonbasle RxJava
35. #CallBackHell @simonbasle Netflix OpenSource
36. #CallBackHell @simonbasle le pendant du Iterable - Iterator
37. #CallBackHell @simonbasle Iterable - Iterator devient Observable - Observer
38. #CallBackHell @simonbasle Iterable - Iterator devient Observable - Observer “Pull” “Push”
39. #CallBackHell @simonbasle composer
40. #CallBackHell @simonbasle composer des programmes asynchrones basés sur les événements
41. #CallBackHell @simonbasle composer des programmes asynchrones basés sur les événements en utilisant des séquences observables
42. #CallBackHell @simonbasle abstraire l’aspect concurrent
43. #CallBackHell @simonbasle tout est Observable sous le capot : pool de threads, acteurs, peu importe
44. #CallBackHell @simonbasle Flexibilité ...on gère...
45. #CallBackHell @simonbasle Flexibilité ...on gère... les valeurs uniques
46. #CallBackHell @simonbasle Flexibilité ...on gère... les séquences
47. #CallBackHell @simonbasle Flexibilité ...on gère... les flux infinis
48. #CallBackHell @simonbasle Flexibilité 3-en-1
49. #CallBackHell @simonbasle the Reactive Manifesto reactivemanifesto.org
50. #CallBackHell @simonbasle reactive-streams.org standardiser sur la jvm
51. #CallBackHell @simonbasle reactive-streams.org standardiser sur la jvm akka - reactor - rxjava
52. #CallBackHell @simonbasle Montre-moi Comment ça Marche !
53. #CallBackHell @simonbasle interface Observer<T>
54. #CallBackHell @simonbasle interface Observer<T> onNext(T data)
55. #CallBackHell @simonbasle interface Observer<T> onNext(T data) onCompleted()
56. #CallBackHell @simonbasle interface Observer<T> onNext(T data) onCompleted() onError(Throwable t)
57. #CallBackHell @simonbasle interface Observer<T> onNext(T data) onCompleted() onError(Throwable t)
58. #CallBackHell @simonbasle Observable<T>
59. #CallBackHell @simonbasle Observable<T> implémenté ou créé
60. #CallBackHell @simonbasle Observable<T> Observable.from(T… values);
61. #CallBackHell @simonbasle Observable<T> Observable.just(T oneValue);
62. #CallBackHell @simonbasle Observable<T> permet de s’abonner
63. #CallBackHell @simonbasle Observable<T> monObservable.subscribe(someObserver);
64. #CallBackHell @simonbasle Observable<T> permet de composer
65. #CallBackHell @simonbasle map flatMap ... Transformer
66. #CallBackHell @simonbasle filter skip distinct ... Filtrer
67. #CallBackHell @simonbasle merge zip reduce ... Combiner
68. #CallBackHell @simonbasle onErrorReturn onErrorResumeNext ... Gérer les Erreurs
69. #CallBackHell @simonbasle groupBy buffer distinctUntilChanged takeLast elementAt concat mergeDelayError retry
70. #CallBackHell @simonbasle Tellement de Choix !
71. #CallBackHell @simonbasle Je suis perdu ça donne quoi concrètement ?
72. #CallBackHell @simonbasle Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(new Func1<Document, Boolean>() { public Boolean call(Document doc) { return doc.isStarred(); }}) .take(10) .map(new Func1<Document, JsonObject>() { public JsonObject call(Document doc) { Observable<JsonObject> oc = CommentService.findForDoc(doc) .map(new Func1<Comment, JsonObject>() { public JsonObject call(Comment c) { User u = UserService.find(c.getUserId()) .toBlockingObservable().first(); JsonObject result = jsonify(c).append("author", u.getName()); return result.append("nickname", u.getLogin()).append("email", u.getEmail()); }}); Observable<JsonObject> om = MetaService.findForDoc(doc) .map(new Func1<Meta, JsonObject>() { public JsonObject call(Meta m) { return jsonify(m); }}); Observable<JsonObject> op = PictureService.findAllMetas(doc.getPictures()) .map(new Func1<PicMeta, JsonObject>() { public JsonObject call(PicMeta p) { return jsonify(p); }});
73. #CallBackHell @simonbasle Func2<JsonArray, JsonObject, JsonArray> arrayAggregator = new Func2<JsonArray, JsonObject, JsonArray>() { public JsonArray call(JsonArray t1, JsonObject t2) { return t1.addElement(t2); }}; JsonObject docJson = new JsonObject().appendInt("id", doc.getId()).append("text", doc.getText()); JsonArray c = new JsonArray(); docJson.addArray("comments", c); oc.reduce(c, arrayAggregator); JsonArray m = new JsonArray(); docJson.addArray("meta", m); om.reduce(m, arrayAggregator); JsonArray p = new JsonArray(); docJson.addArray("pictures", p); op.reduce(p, arrayAggregator); return docJson; } });
74. #CallBackHell @simonbasle On voit toujours rien #CallBackHell @simonbasle
75. #CallBackHell @simonbasle Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(new Func1<Document, Boolean>() { public Boolean call(Document doc) { return doc.isStarred(); }}) .take(10) .map(new Func1<Document, JsonObject>() { public JsonObject call(Document doc) { Observable<JsonObject> oc = CommentService.findForDoc(doc) .map(new Func1<Comment, JsonObject>() { public JsonObject call(Comment c) { User u = UserService.find(c.getUserId()) .toBlockingObservable().first(); JsonObject result = jsonify(c).append("author", u.getName()); return result.append("nickname", u.getLogin()).append("email", u.getEmail()); }}); Observable<JsonObject> om = MetaService.findForDoc(doc) .map(new Func1<Meta, JsonObject>() { public JsonObject call(Meta m) { return jsonify(m); }}); Observable<JsonObject> op = PictureService.findAllMetas(doc.getPictures()) .map(new Func1<PicMeta, JsonObject>() { public JsonObject call(PicMeta p) { return jsonify(p); }});
76. #CallBackHell @simonbasle Func2<JsonArray, JsonObject, JsonArray> arrayAggregator = new Func2<JsonArray, JsonObject, JsonArray>() { public JsonArray call(JsonArray t1, JsonObject t2) { return t1.addElement(t2); }}; JsonObject docJson = new JsonObject().appendInt("id", doc.getId()).append("text", doc.getText()); JsonArray c = new JsonArray(); docJson.addArray("comments", c); oc.reduce(c, arrayAggregator); JsonArray m = new JsonArray(); docJson.addArray("meta", m); om.reduce(m, arrayAggregator); JsonArray p = new JsonArray(); docJson.addArray("pictures", p); op.reduce(p, arrayAggregator); return docJson; } });
77. #CallBackHell @simonbasle filter on doc.isStarred()
78. #CallBackHell @simonbasle take(10)
79. #CallBackHell @simonbasle map( meta to Json)
80. #CallBackHell @simonbasle map( pictures to Json)
81. #CallBackHell @simonbasle map( comments to Json)
82. #CallBackHell @simonbasle map( comments to Json) flattened with User
83. #CallBackHell @simonbasle reduce streams of Json to single arrays
84. #CallBackHell @simonbasle c’est mieux structuré et on a pas mal de bruit en fait Mmh OK
85. #CallBackHell @simonbasle Java 8 la cerise sur le gâteau
86. #CallBackHell @simonbasle Java 8 la cerise sur le gâteau
87. #CallBackHell @simonbasle la version hyper courte
88. #CallBackHell @simonbasle la version hyper courte
89. #CallBackHell @simonbasle la version hyper courte
90. #CallBackHell @simonbasle fonctions de 1ère classe
91. #CallBackHell @simonbasle interfaces fonctionnelles public interface Func1<A, B> { public B call(A from); }
92. #CallBackHell @simonbasle interfaces fonctionnelles public interface Func1<A, B> { public B call(A from); } // ^ une méthode unique
93. #CallBackHell @simonbasle classes anonymes
94. #CallBackHell @simonbasle classes anonymes LAM BDAS
95. #CallBackHell @simonbasle lambdas
96. #CallBackHell @simonbasle new Func1<String, Integer>() { public Integer call(String from) { return from.length(); } } lambdas
97. #CallBackHell @simonbasle (String s) -> { return s.length(); } lambdas
98. #CallBackHell @simonbasle s -> s.length() lambdas
99. #CallBackHell @simonbasle on va pouvoir éliminer le code superflu
100. #CallBackHell @simonbasle Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(new Func1<Document, Boolean>() { public Boolean call(Document doc) { return doc.isStarred(); } });
101. #CallBackHell @simonbasle Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(doc -> doc.isStarred());
102. #CallBackHell @simonbasle Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(doc -> doc.isStarred()) .take(10) .map(doc -> { Observable<JsonObject> oc = CommentService.findForDoc(doc) .map(c -> { User u = UserService.find(c.getUserId()).toBlockingObservable().first(); JsonObject result = jsonify(c).append("author", u.getName()); return result.append("nickname", u.getLogin()).append("email", u.getEmail());}); Observable<JsonObject> om = MetaService.findForDoc(doc).map(m -> jsonify(m)); Observable<JsonObject> op = PictureService.findAllMetas(doc.getPictures()).map(p -> jsonify(p)); JsonObject docJson = new JsonObject().appendInt("id", doc.getId()).append("text", doc.getText()); JsonArray c = new JsonArray(); docJson.addArray("comments", c); oc.reduce(c, (array, elem) -> array.addElement(elem)); JsonArray m = new JsonArray(); docJson.addArray("meta", m); om.reduce(m, (array, elem) -> array.addElement(elem)); JsonArray p = new JsonArray(); docJson.addArray("pictures", p); op.reduce(p, (array, elem) -> array.addElement(elem)); return docJson; });
103. #CallBackHell @simonbasle 2 1 slides en taille 10 58 28 lignes de code max 7 4 tabulations 3 1 imbrication exceptionnelle
104. #CallBackHell @simonbasle on a bien dégrossi notre code
105. #CallBackHell @simonbasle TakeAway
106. #CallBackHell @simonbasle du code Asynchrone
107. #CallBackHell @simonbasle sans Callbacks
108. #CallBackHell @simonbasle avec un minimum de pollution visuelle
109. #CallBackHell @simonbasle lisible et compréhensible
110. #CallBackHell @simonbasle Hope you’ll love it too !
111. #CallBackHell @simonbasle
112. #CallBackHell @simonbasle Merci!
113. #CallBackHell @simonbasle Crédits ➔ The Door to Hell - Flydime http://www.flickr.com/photos/flydime/4671890969/ ➔ Cat Attack - Static416 http://www.flickr.com/photos/ehacke/4584255926/ ➔ Série Stormtroopers - J.D. Hancock http://photos.jdhancock.com/series/stormtroopers.html ➔ Chien de près - RPavich http://www.flickr.com/photos/rpavich/11409595543/ ➔ Hyperspace - Procsilas Moscas http://www.flickr.com/photos/procsilas/12821454664/ ➔ Takeaway - Edimbhurg Blog http://www.flickr.com/photos/theedinburghblog/6493647769/ ➔ The End Sable - Elektro-Plan http://pixabay.com/p-283407/ By-Sa By-Nc By By By By Cc0