Vavr - functional Java the easy way

Transcript

1. @koenighotze Revenge of the JavaSlang
2. @koenighotze David Schmitz - @koenighotze
3. @koenighotze Sticker construction kit
4. @koenighotze
5. @koenighotze
6. @koenighotze What’s in it for you?
7. @koenighotze Functional programming is hip How VAVR helped us Lot’s of code - OMG!
8. @koenighotze Functors, applicatives, monads stay home
9. @koenighotze Code that is easier to reason about
10. @koenighotze Side-effects are evil
11. @koenighotze try { int i = 1/0; } catch (Throwable t) { … } Exceptions are goto-statements :(
12. @koenighotze Referential Transparency
13. @koenighotze Math.random(); Math.max(1, 2); Math.random(); Math.max(1, 2); Pure functions are a Good ThingTm :(
14. @koenighotze Thinking in values
15. @koenighotze Immutability Performance Safety
16. @koenighotze In a nutshell, think about “what to code“ not “how to code”
17. @koenighotze Enter Java eight
18. @koenighotze (a) -> a + 2 list.stream().filter… Excitement…
19. @koenighotze until…
20. @koenighotze Try filtering all invalid users from a list of users
21. @koenighotze users.stream() .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
22. @koenighotze import static io.vavr.API.*;
23. @koenighotze Immutable collections Some functional sugar Functional exception handling Pattern matching Property based testing Circuit breaker
24. @koenighotze Before we get to the details… Let’s fix that ugly code
25. @koenighotze users.stream() .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
26. @koenighotze List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
27. @koenighotze List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
28. @koenighotze List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}); .collect(Collectors.toLis t());
29. @koenighotze List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}); .collect(Collectors.toLis t());
30. @koenighotze List.ofAll(users) .filter(user -> Try.of(user::validate) .getOrElse(false) ); } catch (IllegalStateException ex) { return ); .collect(Collectors.toList();
31. @koenighotze List.ofAll(users) List.filter(user -> Try.of(user::validate) .getOrElse(false));
32. @koenighotze immutable Collections
33. @koenighotze Mutable Collections are Evil
34. @koenighotze Returning void == side-effect! interface Collection<E> { … void clear(); } interface Collection<E> { … void clear(); }
35. @koenighotze Collections .unmodifiableList(list); .add(“”)
36. @koenighotze Collections .unmodifiableList(list) .add(“”);
37. @koenighotze Painting by Gustav Courbet java.lang.UnsupportedOperationException at java.util.Collections$UnmodifiableCollection .add(Collections.java:1055) at java.util.stream.AbstractPipeline.<init> (AbstractPipeline.java:203) at java.util.stream.ReferencePipeline.<init> (ReferencePipeline.java:94)
38. @koenighotze https://cdn.infoq.com/statics_s2_20170314-0434/resource/news/2016/11/the-road-to-javaslang-3/en/resources/1infoq-version2.0-library.png
39. @koenighotze Functional data structures
40. @koenighotze Immutable Referentially transparent Persistent
41. @koenighotze Effectively immutable
42. heroes = List.of("Han", "Luke") Cons@661 “Han” T Cons@666 “Luke” () heroes
43. Cons@661 “Han” T Cons@666 “Luke” () heroes Cons@662 “Ben” T more more = heroes.prepend("Ben")
44. droids = TreeSet.of( "C3PO", "R2D2", "K2SO" ) Node@676 Node@679 Node@681 “K2SO” () () “C3PO” () () “R2D2”
45. droids.add("Chopper");
46. Node@689 Node@691 () Node@694 () () “Chopper” Node@676 Node@679 Node@681 “K2SO” () () “C3PO” () () “R2D2”
47. Checking for updates?
48. old == new
49. @koenighotze Streams are glorified iterators
50. @koenighotze Stream<String> jdk = Stream.of("a", “B"); jdk.map(String::toUpperCase); jdk.map(String::toLowerCase);
51. @koenighotze Painting by Gustav Courbet java.lang.IllegalStateException: stream has already been operated upon or closed at java.util.stream.AbstractPipeline.<init> (AbstractPipeline.java:203) at java.util.stream.ReferencePipeline.<init> (ReferencePipeline.java:94)
52. @koenighotze vavr streams
53. Stream<String> vavr = Stream.of("a", "B"); slang.map(String::toUpperCase); // “A”,“B” slang.map(String::toLowerCase); // “a”,“b”
54. @koenighotze Stream<String> vavr = Stream.of("a", "B"); vavr.map(String::toUpperCase) .take(2); vavr.map(String::toLowerCase) .take(2);
55. @koenighotze Stream<String> vavr = Stream.of("a", "B"); vavr.map(String::toUpperCase) .take(2);// “A”,“B” vavr.map(String::toLowerCase) .take(2);// “a”,“b”
56. @koenighotze Better performance Less unexpected behaviour
57. @koenighotze functional Sugar
58. @koenighotze find a user and, if an address is available, fetch the user’s street
59. @koenighotze User user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
60. @koenighotze Cascading Pile of Shame
61. @koenighotze optional
62. @koenighotze Optional<User> opt = Optional.ofNullable(user); if (opt.isPresent()) { User user = opt.get(); }
63. And now, young coder... you will die.
65. @koenighotze map or flatmap There is no isPresent()
66. @koenighotze optional or option
67. @koenighotze Optional
68. @koenighotze Option Some None
69. @koenighotze Option Some None Value Iterable
70. @koenighotze Option Some None Value Iterable
71. @koenighotze Option Some None Value Iterable Serializable
72. @koenighotze option is A Gift Box
73. @koenighotze None Some
74. @koenighotze Map opens the Gift Box
75. @koenighotze Map Some Some ( )->
76. @koenighotze nothing from nothing
77. @koenighotze ( )-> Map None None
78. @koenighotze Fixing the Pile of Shame
79. @koenighotze User user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
80. @koenighotze User user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
81. @koenighotze Option<User> user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
82. @koenighotze Option<User> user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
83. @koenighotze Option<User> user = repo.findOne("id"); user.flatMap(User::getAddress) Address address = user.getAddress(); if (null != address) { return address.getStreet(); } } Option<User> user = repo.findOne("id"); user.flatMap(User::getAddress) Address address = user.getAddress(); if (null != address) { return address.getStreet(); } } Option<Address> getAddress()
84. @koenighotze Option<User> user = repo.findOne("id"); user.flatMap(User::getAddress) Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
85. @koenighotze Option<User> user = repo.findOne("id"); user.flatMap(User::getAddress) Address address = user.getAddress(); .map(Address::getStreet) return address.getStreet(); } }
86. repo.findOne("id") .flatMap(User::getAddress) .map(Address::getStreet) .getOrElse("");
87. @koenighotze option.of(value) .map(nested code) == understandable story
88. @koenighotze functional exception Handling
89. @koenighotze validation like back in the days
90. @koenighotze public static String check(String iban){ if (validationMagic(iban)) { return iban; } throw new IllegalArgumentException(“Peng”); }
91. @koenighotze Partial function
92. @koenighotze Awesome WTF Code
93. @koenighotze String iban; try { iban = check(“AL47…”); } catch (IllegalArgumentException ex) { iban = ""; }
94. @koenighotze Lifting Exceptions to options
95. @koenighotze total function
96. @koenighotze String iban = lift(Iban::check) .apply("AL47...") .getOrElse("");
97. @koenighotze String iban = lift(Iban::check) .apply("AL47...") .getOrElse("");
98. @koenighotze Wrapping Exceptions with Try
99. @koenighotze Try.of(() -> stuffToDo())
100. @koenighotze Failure Exception Success Result Try.of(() -> stuffToDo())
101. @koenighotze Try.of(() -> check("AL..")) .getOrElse("")
102. @koenighotze Try.of(() -> check("AL..")) .getOrElse("")
103. @koenighotze Lifting and Try-ing reduce exception handling clutter and side-effects
104. @koenighotze Structural decomposition
105. @koenighotze Structural decomposition discouraged! http://cr.openjdk.java.net/ ~briangoetz/amber/pattern- match.html
106. @koenighotze (?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=? ^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23- \x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?: [a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a- z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9] [0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a- z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21- \x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\]) Pattern Matching Basics
107. @koenighotze Match(expression) .of(cases)
108. @koenighotze Case(pattern, function)
109. @koenighotze $() wildcard pattern $(“foo”) equals pattern isIn(“a”, “b”) conditional pattern
110. @koenighotze Classic HTTP Handling
111. @koenighotze if (OK.equals(res.getStatusCode())) { return res.getBody(); } return emptyList();
112. @koenighotze Functional version
113. @koenighotze Note: some type details missing Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 );
114. @koenighotze Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 ); Note: some type details missing OK or anything else
115. @koenighotze Note: some type details missing Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 );
116. @koenighotze Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 ); Note: some type details missing
117. @koenighotze Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 ); Note: some type details missing
118. @koenighotze Matching a Try
119. @koenighotze public Try<…> fetchFromUrl(…) { … }
120. @koenighotze Match(fetchFromUrl(“…”)) .of( Case(Success($()), identity()), Case(Failure($()), emptyList()) );
121. @koenighotze Match(fetchFromUrl(“…”)) .of( Case(Success($()), identity()), Case(Failure($()), emptyList()) );
122. @koenighotze Match(fetchFromUrl(“…”)) .of( Case($Success($()), identity()), Case($Failure($()), emptyList()) );
123. @koenighotze Match(fetchFromUrl(“…”)) .of( Case($Success($()), identity()), Case($Failure($()), emptyList()) );
124. @koenighotze Pattern matching replaces complex if- then-else sequences with clear expressions
125. @koenighotze property tEST
126. @koenighotze property Based - The idea
127. @koenighotze Declarative, infinite test cases Have you tested for all characters… …even for ? Have you tested usernames like… ౧ప唆⏑㐿䯰㨼ᮁ娤㮘?搃蘸阁㌃ᡧ㫈葷㖒ܪ匘ᤫ䳴㻅 ⦷♻痯ヲ㙃銐璚ೃⶕᄰ 䩰㒭㙵闆䩟嗀嗀侀
128. @koenighotze vavr property test
129. @koenighotze Property.def(“Something works”) .forAll(Generated Data) .suchThat(Checked Function) .check() .assertIsSatisfied();
130. @koenighotze Arbitrary<String> arbitraryUnicodeId() { Gen<Character> id = r -> (char) r.nextInt(); return Arbitrary.string(id); }
131. @koenighotze Arbitrary<String> arbitraryUnicodeId() { Gen<Character> id = r -> (char) r.nextInt(); return Arbitrary.string(id); }
132. @koenighotze Property .def("Should not go boom”) .forAll(arbitraryUnicodeString()) .suchThat(id -> isOkOrNotFound(id)) .check() .assertIsSatisfied();
133. @koenighotze 2017-03-21 10:45:59.913 INFO 45701 --- FrameworkServlet '': initialization started 2017-03-21 10:45:59.925 INFO 45701 --- FrameworkServlet '': initialization completed in 12 ms Storing User@217b0952[username=rwxbeoigyesbeqqz,email=W`a@0c..-.--db-.T5-.2-g, Storing User@4e6280de[username=vptafghfwuwwrwall,email=sByP@6jLA4.J.1c..5h269O3-1M6-c6...-.-,,, Storing User@2fca282c[username=qmhkjdtvbtjzfciwcceqgzfznzkhhcokiyoipdefbr,email=Q96!@6.n8. Storing User@64d53f0d[publicId=e9d7a121-9f23-483a-828a-f9e3045fc297,username=unflrpvztxtmi... ... Storing User@1b10f60e[publicId=6f084c18-415c-42c4-b1a8-00c5c1fc9e67,username=xwhpdpjowirsmjym... Storing User@4b916cc2[publicId=a2b9db2c-0189-4fe8-843d-e709ef3886fa,username=yxdidpexnayyjpzo... Should not go boom: OK, passed 1000 tests in 3719 ms.
134. @koenighotze Should not go boom: Falsified after 23 passed tests in 3005 ms. java.lang.AssertionError: Expected satisfied check result but was Falsified(…, sample = ( 䒖 ꜏, 燤䠽㏊密ᵓ〞খﾡ ꌎ ⬆鹮 ۄ鄽㏫魨 ࠞ⽆⢕ 㣁㸎Ԩ 䏨➰ìឧ寅罟 溌椡ﲡࣇ欙ㄓῴﯯ缲ꢶꇞ⌽ꪂ惗 㛨蘄䏄⩂粻ㇼ?ವ㝓㭃, fzqlbkljxhfrghllzcthvgqiglaabihkzgsqwgfcichamyonmayiewwsfwmw ntzvozqqydkqillhpyi, +g4@F.8yOkj.-....C6GUP..3.4.-..h- V74.E.-----2T.z97..3f1ZM6))
135. @koenighotze functional resilience
136. @koenighotze Circuit breaker one-o-one
137. @koenighotze Consumer Backend
138. @koenighotze Fallback Resilience decorator Closed Open Half-Open Consumer Backend
139. @koenighotze Resilience decorator Closed Open Half-Open Consumer Fallback
140. @koenighotze Fallback Resilience decorator Closed Open Half-Open Consumer
141. @koenighotze Fallback Resilience decorator Closed Open Half-Open Consumer
142. @koenighotze Resilience For J
143. @koenighotze Backend Consumer Backend Service Resilience decorator Circuit Breaker Retry Cache
144. @koenighotze Option<…> fetchBoard(String id) { result = restTemplate.getForEntity(…); return Match(result.getStatusCode()) .option(…); }
145. @koenighotze Option<…> fetchBoard(String id) { result = restTemplate.getForEntity(…); return Match(result.getStatusCode()) .option(…); }
146. @koenighotze CircuitBreaker .decorateCheckedFunction( circuitBreaker, db::fetchBoard);
147. @koenighotze Try.of(() -> decorated.apply(stationId)) .getOrElse(empty())
148. @koenighotze The last monad?
149. @koenighotze http://www.vavr.io/
150. @koenighotze Spring data integration
151. @koenighotze interface UserRepository extends MongoRepository<User, String> { Option<User> findByPublicId(String publicId); Seq<User> findByLastname(String lastname); }
152. @koenighotze interface UserRepository extends MongoRepository<User, String> { Option<User> findByPublicId(String publicId); Seq<User> findByLastname(String lastname); }
153. @koenighotze Resilience for J
154. @koenighotze CircuitBreaker .decorateCheckedFunction( circuitBreaker, db::fetchBoard);
155. @koenighotze Property based tests
156. @koenighotze Property .def("Should not go boom”) .forAll(arbitraryUnicodeString()) .suchThat(id -> isFoundOrNotFound(id)) .check() .assertIsSatisfied();
157. @koenighotze So, is this is the mother of all free lunches?
158. @koenighotze What are the drawbacks?
159. @koenighotze
160. @koenighotze count(Collection-libs) > count(Logging-libs)
161. @koenighotze Option.of(foo) .map .filter .flatMap .map .flatMap .getOrElse(null) N O T a drawback!
162. @koenighotze version one
163. @koenighotze Modularization Alignment with Java 9 Obsolete pattern match (maybe) http://blog.vavr.io/fast-forward-to-vavr-1-0/
164. @koenighotze Wrapping up
165. @koenighotze Slick, stable, non-invasive, consistent API Object-functional advantages now Complex(?) Property test(?) Pattern match(?)
166. @koenighotze RESIST THE TYRANNY OF THE COLLECTIONS FRAMEWORK JOIN THE RESISTANCE!
167. @koenighotze thank you @Koenighotze