Vavr Java User Group Rheinland
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Wolltest du schon immer die Vorteile und Ideen von Scala in deinen Java oder Kotlin Projekten nutzen? Dann ist Vavr (ehemals Javaslang) genau die richtige Bibliothek für dich. Anhand echter Projektbeispiele schauen wir uns den Nutzen an, den Vavr mit seinen syntaktischen Erweiterungen und Features bei der täglichen Arbeit bietet. Wir schauen uns Value Types, echte funktionale Datentypen an und werden lernen, wie wir Exceptions sinnvoller behandeln können. Alles für besser wartbaren und sauberen Code! Vavr bietet die Möglichkeit, die Vorteile objekt-funktionaler Programmierung zu nutzen, ohne Java den Rücken kehren zu müssen.
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Vavr Java User Group Rheinland
- 1. @koenighotze Revenge of the JavaSlang
- 3. @koenighotze
- 4. @koenighotze Finding a new name
- 5. @koenighotze
- 6. @koenighotze
- 7. @koenighotze What’s in it for you?
- 8. @koenighotze Functional programming is hip How VAVR helped us Some awful code - OMG!
- 10. @koenighotze Code that is easier to reason about
- 12. @koenighotze try { int i = 1/0; } catch (Throwable t) { … } Exceptions are goto-statements :(
- 14. @koenighotze Math.random(); Math.max(1, 2); Math.random(); Math.max(1, 2); Pure functions are a Good ThingTm :(
- 17. @koenighotze In a nutshell, think about “what to code“ not “how to code”
- 19. @koenighotze (a) -> a + 2 list.stream().filter… Excitement…
- 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. @koenighotzePainting by Gustav Courbet WAAAAAAT?
- 24. @koenighotze Immutable collections Some functional sugar Functional exception handling
- 25. @koenighotze Before we get to the details… Let’s fix that ugly code
- 26. @koenighotze users.stream() .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.toList());
- 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 { return user.validate(); } catch (Exception ex) { return false; }}); .collect(Collectors.toLis t());
- 31. @koenighotze List.ofAll(users) .filter(user -> Try.of(user::validate) .getOrElse(false) ); } catch (IllegalStateException ex) { return ); .collect(Collectors.toList();
- 35. @koenighotze Returning void == side-effect! interface Collection<E> { … void clear(); } interface Collection<E> { … void clear(); }
- 38. @koenighotzePainting 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)
- 40. @koenighotze Functional data structures Effectively immutable
- 41. heroes = List.of("Han", "Luke") Cons@661 “Han” T Cons@666 “Luke” () heroes
- 42. Cons@661 “Han” T Cons@666 “Luke” () heroes Cons@662 “Ben” Tmore more = heroes.prepend("Ben")
- 43. droids = TreeSet.of( "C3PO", "R2D2", "K2SO" ) Node@676 Node@679 Node@681“K2SO” () ()“C3PO” () ()“R2D2”
- 45. Node@689 Node@691 () Node@694 () ()“Chopper” Node@676 Node@679 Node@681“K2SO” () ()“C3PO” () ()“R2D2”
- 47. old == new
- 49. @koenighotze Stream<String> jdk = Stream.of("a", “B"); jdk.map(String::toUpperCase); jdk.map(String::toLowerCase);
- 50. @koenighotzePainting 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. Stream<String> vavr = Stream.of("a", "B"); slang.map(String::toUpperCase); // “A”,“B” slang.map(String::toLowerCase); // “a”,“b”
- 53. @koenighotze Stream<String> vavr = Stream.of("a", "B"); vavr.map(String::toUpperCase) .take(2); vavr.map(String::toLowerCase) .take(2);
- 54. @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 Bonus shout-out to @pivovarit: https://git.io/fj4Od
- 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 (address != null) { return address.getStreet(); } }
- 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()
- 72. @koenighotze Option is a gift box
- 74. @koenighotze Map opens the gift box
- 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(); } }
- 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”); }
- 92. @koenighotze String iban; try { iban = check(“AL47…”); } catch (IllegalArgumentException ex) { iban = ""; }
- 94. @koenighotze Strings that are valid IBANs
- 95. @koenighotze Strings that are valid IBANs public static String check(String iban){ if (validationMagic(iban)) { return iban; } throw new IllegalArgumentException(“Peng”); } Partial function
- 97. @koenighotze Partial function Strings that are valid IBANs public static String check(String iban){ if (validationMagic(iban)) { return iban; } throw new IllegalArgumentException(“Peng”); }
- 98. @koenighotze Strings that are valid IBANs Total function lift() All possible strings public static String check(String iban){ if (validationMagic(iban)) { return iban; } throw new IllegalArgumentException(“Peng”); } Partial function
- 99. @koenighotze String iban = lift(Iban::check) .apply("AL47...") .getOrElse("");
- 100. @koenighotze String iban = lift(Iban::check) .apply("AL47...") .getOrElse("");
- 106. @koenighotze try { ByteArrayOutputStream logo = readLogo(url); return fetchSuccessful(logo); } catch (InterruptedException | TimeoutException e) { return timedoutResponse(); } catch (ExecutionException e) { return fetchFailed(); }
- 107. @koenighotze try { ByteArrayOutputStream logo = readLogo(url); return fetchSuccessful(logo); } catch (InterruptedException | TimeoutException e) { return timedoutResponse(); } catch (ExecutionException e) { return fetchFailed(); }
- 108. @koenighotze try { ByteArrayOutputStream logo = readLogo(url); return fetchSuccessful(logo); } catch (InterruptedException | TimeoutException e) { return timedoutResponse(); } catch (ExecutionException e) { return fetchFailed(); }
- 109. @koenighotze try { ByteArrayOutputStream logo = readLogo(url); return fetchSuccessful(logo); } catch (InterruptedException | TimeoutException e) { return timedoutResponse(); } catch (ExecutionException e) { return fetchFailed(); }
- 115. @koenighotze Lifting and Try-ing reduce exception handling clutter and side-effects
- 116. @koenighotze “It’s just like the Schrodinger’s cat story, you keep working with the box and delay opening it up until it’s completely necessary to know what’s happening in there.” — Maurício Linhares
- 121. @koenighotze Declarative, infinite test cases Have you tested for all characters… …even for 💩? Have you tested usernames like… ౧ప唆⏑쀋䯰㨼ᮁ娤즶?搃蘸阁뺬ᡧ㫈葷㖒ܪ匘ᤫ䳴㻅 댇껓痯믶㙃銐璚풔랾ᄰ 䩰삀싲闆䩟嗀嗀侀
- 123. @koenighotze Property.def(“Something works”) .forAll(Generated Data) .suchThat(Checked Function) .check() .assertIsSatisfied();
- 124. @koenighotze Arbitrary<String> arbitraryUnicodeId() { Gen<Character> id = r -> (char) r.nextInt(); return Arbitrary.string(id); }
- 125. @koenighotze Arbitrary<String> arbitraryUnicodeId() { Gen<Character> id = r -> (char) r.nextInt(); return Arbitrary.string(id); }
- 126. @koenighotze Property .def("Should not go boom”) .forAll(arbitraryUnicodeString()) .suchThat(id -> isOkOrNotFound(id)) .check() .assertIsSatisfied();
- 127. @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.
- 128. @koenighotze Should not go boom: Falsified after 23 passed tests in 3005 ms. java.lang.AssertionError: Expected satisfied check result but was Falsified(…, sample = ( 풧 ꜏, 燤䠽뾌密ᵓ뫶খﾡ ꌎ ⬆鹮 라鄽뾮魨 붐맧놌 엍첮Ԩ䏨 ➰ìឧ寅罟 溌椡ﲡ셋欙밶ῴﯯ缲ꢶꇞ⌽ꪂ惗 쎂蘄펮뎷粻뵞?푠쏽쥎, fzqlbkljxhfrghllzcthvgqiglaabihkzgsqwgfcichamyonmayiewwsfwmw ntzvozqqydkqillhpyi, +g4@F.8yOkj.-....C6GUP..3.4.-..h- V74.E.-----2T.z97..3f1ZM6))
- 138. @koenighotze Option<…> fetchBoard(String id) { result = restTemplate.getForEntity(…); return Match(result.getStatusCode()) .option(…); }
- 139. @koenighotze Option<…> fetchBoard(String id) { result = restTemplate.getForEntity(…); return Match(result.getStatusCode()) .option(…); }
- 145. @koenighotze interface UserRepository extends MongoRepository<User, String> { Option<User> findByPublicId(String publicId); Seq<User> findByLastname(String lastname); }
- 146. @koenighotze interface UserRepository extends MongoRepository<User, String> { Option<User> findByPublicId(String publicId); Seq<User> findByLastname(String lastname); }
- 147. @koenighotze So, is this is the mother of all free lunches?
- 149. @koenighotze
- 151. @koenighotze Option.of(foo) .map .filter .flatMap .map .flatMap .getOrElse(null) N O T a drawback!
- 153. @koenighotze Modularization Alignment with Java 9 Obsolete pattern match (maybe) http://blog.vavr.io/fast-forward-to-vavr-1-0/
- 155. @koenighotze Slick, stable, non-invasive, consistent API Object-functional advantages now Complex(?) Property test(?) Pattern match(?)
- 156. @koenighotze RESISTTHE TYRANNY OF THE COLLECTIONS FRAMEWORK JOIN THE RESISTANCE!
- 157. @koenighotze Thank you! https://git.io/fj855 All Star Wars related images are copyright Disney Corp.