RxJava + Java 8, Sortir de l'Enfer des Callbacks

[FR] Comment faire du code asynchrone, lisible et composable? RxJava couplé à Java8 pourrait être une bonne solution pour sortir de cet Enfer des Callbacks.

1. Sortir de l’Enfer des Callbacks RxJava + Java 8
2. @SimonBasle @Couchbase @InfoQFR @bbl_fr
3. L‘Enfer des Callbacks?
4. L‘Enfer des Callbacks?
5. synchrone == inefficace*
6. nous avons besoin de code asynchrone
7. nous avons besoin de code asynchrone réactif
8. nous avons besoin de code asynchrone parallélisable
9. nous avons besoin de code asynchrone composable
10. nous avons besoin de code asynchrone lisible
11. mais comment bien faire Asynchrone ?
12. les Futures<T>
13. les Futures<T> une modélisation lisible
14. les Futures<T> peuvent bloquer (get)
15. les Futures<T> deviennent compliquées au delà d’un niveau
16. les Futures<T> se composent mal
17. les Callbacks
18. les Callbacks tout simple
19. les Callbacks pas de blocage possible
20. les Callbacks ne se composent pas
21. les Callbacks deviennent vite illisibles
22. EXEMPLE : je veux mes 10 premiers docs marqués comme favoris sous forme de json complet
23. Pour ça je dois agréger en asynchrone : méta commentaires & auteurs description d’images
24. 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. // … 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. 2 slides en taille 10 58 lignes de code max 7 tabulations
27. jusqu’à 3 Callbacks imbriqués 2 usages de CountDownLatch
28. 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. 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. 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. 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. Wow Such Space! 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. RxJava
34. RxJava
35. Netflix OpenSource
36. le pendant du Iterable - Iterator
37. Iterable - Iterator devient Observable - Observer
38. Iterable - Iterator devient Observable - Observer “Pull” “Push”
39. composer
40. composer des programmes asynchrones basés sur les événements
41. composer des programmes asynchrones basés sur les événements en utilisant des séquences observables
42. abstraire l’aspect concurrent
43. tout est Observable sous le capot : pool de threads, acteurs, peu importe
44. Flexibilité ...on gère...
45. Flexibilité ...on gère... les valeurs uniques
46. Flexibilité ...on gère... les séquences
47. Flexibilité ...on gère... les flux infinis
48. Flexibilité 3-en-1
49. the Reactive Manifesto reactivemanifesto.org
50. reactive-streams.org standardiser sur la jvm
51. reactive-streams.org standardiser sur la jvm akka - reactor - rxjava
52. Montre-moi Comment ça Marche !
53. interface Observer<T>
54. interface Observer<T> onNext(T data)
55. interface Observer<T> onNext(T data) onCompleted()
56. interface Observer<T> onNext(T data) onCompleted() onError(Throwable t)
57. interface Observer<T> onNext(T data) onCompleted() onError(Throwable t)
58. Observable<T>
59. Observable<T> implémenté ou créé
60. Observable<T> Observable.from(T… values);
61. Observable<T> Observable.from(Iterable<T> itrbl);
62. Observable<T> Observable.just(T oneValue);
63. Observable<Integer> Observable.range(int start, int count);
64. Observable<T> permet de s’abonner
65. Observable<T> monObservable.subscribe(someObserver);
66. Observable<T> permet de composer
67. diagrammes “à billes”
68. beaucoup de diagrammes “à billes”
69. Transformation
70. Observable<R> map(Func1<T, R> func)
71. Observable<R> map(Func1<T, R> func)
72. Observable<R> flatMap(Func1<T, Observable<R>> func)
73. Observable<R> flatMap(Func1<T, Observable<R>> func)
74. Observable<List<T>> buffer(int count)
75. Observable<List<T>> buffer(int count)
76. Observable<T> reduce(Func2<T,T,T> accumulator)
77. Observable<T> reduce(Func2<T,T,T> accumulator)
78. Observable<T> scan(Func2<T,T,T> accumulator)
79. Observable<T> scan(Func2<T,T,T> accumulator)
80. Filtrage
81. Observable<T> take(int n)
82. Observable<T> take(int n)
83. Observable<T> skip(int n)
84. Observable<T> skip(int n)
85. Observable<T> filter(Func1<T, Boolean> predicate)
86. Observable<T> filter(Func1<T, Boolean> predicate)
87. Observable<T> sample(long period, TimeUnit unit)
88. Observable<T> sample(long period, TimeUnit unit)
89. Observable<T> distinct()
90. Observable<T> distinct()
91. Combinaison
92. static Observable<T> concat(Observable<T> t1, Observable<T> t2)
93. static Observable<T> concat(Observable<T> t1, Observable<T> t2)
94. static Observable<T> merge(Observable<T> t1, Observable<T> t2)
95. static Observable<T> merge(Observable<T> t1, Observable<T> t2)
96. Observable<R> zip(Observable<T2> other, Func2<T, T2, R> zipFunction)
97. Observable<R> zip(Observable<T2> other, Func2<T, T2, R> zipFunction)
98. Parallélisme
99. Observable<T> subscribeOn(Scheduler workThere)
100. Observable<T> subscribeOn(Scheduler workThere)
101. Observable<T> observeOn(Scheduler workThere)
102. Observable<T> observeOn(Scheduler workThere)
103. Observable<T> cache()
104. Observable<T> cache()
105. ...
106. Tellement de Choix !
107. Observable<T> permet de gérer les erreurs
108. On a déjà la méthode onError(Throwable t) dans Observer ...
109. ...mais on peut aussi les gérer différemment
110. static Observable<T> mergeDelayError( Observable<T> t1, Observable<T> t2)
111. static Observable<T> mergeDelayError( Observable<T> t1, Observable<T> t2)
112. Observable<T> onErrorReturn(Func1<Throwable, T> fallbackFunction)
113. Observable<T> onErrorReturn(Func1<Throwable, T> fallbackFunction)
114. Observable<T> onErrorResumeNext(Observable<T> fallback)
115. Observable<T> onErrorResumeNext(Observable<T> fallback)
116. Observable<T> retry(int retryCount)
117. Observable<T> retry(int retryCount)
118. Je suis perdu ça donne quoi concrètement ?
119. 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) .flatMap(new Func1<Comment, Observable<JsonObject>>() { public Observable<JsonObject> call(Comment c) { return UserService.find(c.getUserId()) .first() .map(new Func1<User, JsonObject>() { public JsonObject call(User u) { 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); }});
120. Observable<JsonObject> op = PictureService.findAllMetas(doc.getPictures()) .map(new Func1<PicMeta, JsonObject>() { public JsonObject call(PicMeta p) { return jsonify(p); }}); 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; } });
121. On voit toujours rien #CallBackHell @simonbasle
122. 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) .flatMap(new Func1<Comment, Observable<JsonObject>>() { public Observable<JsonObject> call(Comment c) { return UserService.find(c.getUserId()) .first() .map(new Func1<User, JsonObject>() { public JsonObject call(User u) { 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); }});
123. Observable<JsonObject> op = PictureService.findAllMetas(doc.getPictures()) .map(new Func1<PicMeta, JsonObject>() { public JsonObject call(PicMeta p) { return jsonify(p); }}); 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; } });
124. filter on doc.isStarred()
125. take(10)
126. map( meta to Json)
127. map( pictures to Json)
128. map( comments to Json)
129. map( comments to Json) flattened with User
130. reduce streams of Json to single arrays
131. c’est mieux structuré et on a pas mal de bruit en fait Mmh OK
132. Java 8 la cerise sur le gâteau
133. Java 8 la cerise sur le gâteau
134. la version hyper courte
135. la version hyper courte
136. la version hyper courte
137. fonctions de 1ère classe
138. interfaces fonctionnelles public interface Func1<A, B> { public B call(A from); }
139. interfaces fonctionnelles public interface Func1<A, B> { public B call(A from); } // ^ une méthode unique
140. classes anonymes
141. classes anonymes LAM BDAS
142. lambdas
143. new Func1<String, Integer>() { public Integer call(String from) { return from.length(); } } lambdas
144. (String s) -> { return s.length(); } lambdas
145. s -> s.length() lambdas
146. références de méthodes
147. références de méthodes MaClasse::méthodeStatique
148. références de méthodes monInstance::méthodeInstance
149. références de méthodes UnType::méthodeInstanceDuType
150. références de méthodes String::length
151. on va pouvoir éliminer le code superflu
152. Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(new Func1<Document, Boolean>() { public Boolean call(Document doc) { return doc.isStarred(); } });
153. Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(doc -> doc.isStarred());
154. Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(Document::isStarred);
155. Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(Document::isStarred) .take(10) .map(doc -> { Observable<JsonObject> oc = CommentService.findForDoc(doc) .flatMap(c -> UserService.find(c.getUserId()) .first() .map(u -> { 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; });
156. Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(Document::isStarred) .take(10) .map(doc -> { Observable<JsonObject> oc = CommentService.findForDoc(doc) .flatMap(c -> UserService.find(c.getUserId()) .first() .map(u -> { 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; }); Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(Document::isStarred) .take(10)
157. Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(Document::isStarred) .take(10) .map(doc -> { Observable<JsonObject> oc = CommentService.findForDoc(doc) .flatMap(c -> UserService.find(c.getUserId()) .first() .map(u -> { 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; }); Observable<JsonObject> oc = CommentService.findForDoc(doc) .flatMap(c -> UserService.find(c.getUserId()) .first() .map(u -> { JsonObject result = jsonify(c) .append("author", u.getName()); .append("nickname", u.getLogin()) .append("email", u.getEmail()); return result; }) );
158. Observable<JsonObject> fullDocumentJson = DocumentService.find("user") .filter(Document::isStarred) .take(10) .map(doc -> { Observable<JsonObject> oc = CommentService.findForDoc(doc) .flatMap(c -> UserService.find(c.getUserId()) .first() .map(u -> { 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; }); oc.reduce(c, (array, elem) -> array.addElement(elem));
159. 2 1 slides en taille 10 58 23 lignes de code max 7 3 tabulations 3 0 imbrications
160. on a bien dégrossi notre code
161. ah oui mais moi j’ai que Java 5/6/7 5
162. Projet RetroLambda https://github.com/orfjackal/retrolambda
163. now I’m Batman
164. TakeAway
165. du code Asynchrone
166. sans Callbacks
167. avec un minimum de pollution visuelle
168. lisible et compréhensible
169. Hope you’ll love it too !
171. Merci!
172. Crédits ➔ The Door to Hell - By-Sa Flydime http://www.flickr.com/photos/flydime/4671890969 ➔ Cat Attack - By-Nc Static416 http://www.flickr.com/photos/ehacke/4584255926/ ➔ Série Stormtroopers - By J.D. Hancock http://photos.jdhancock.com/series/stormtroopers.html ➔ Marbles Reflected - By ~Pawsitive~Candie_N http://www.flickr.com/photos/scjn/4274713988/ ➔ Marble Diagrams - Apache 2.0 Netflix OSS http://netflix.github.io/ (doc RxJava) ➔ Chien de près - By Rpavich http://www.flickr.com/photos/rpavich/11409595543/ ➔ Hyperspace - By Procsilas Moscas http://www.flickr.com/photos/procsilas/ 12821454664/ ➔ Takeaway - By Edimbhurg Blog http://www.flickr.com/photos/theedinburghblog/ 6493647769/ ➔ The End Sable - Cc0 Elektro-Plan http://pixabay.com/p-283407/