Javaslang

Transcript

1. #Devoxx #Javaslang @koenighotze JΛVΛSLΛNG Functional Sugar For Java
2. #Devoxx #Javaslang @koenighotze Senacor Technologies Programmer! That’s me coding Scala David Schmitz / @koenighotze Senacor Technologies Programmer! That’s me coding Scala
3. #Devoxx #Javaslang @koenighotze What’s in it for you? Functional programming is hip How Javaslang helped us Examples, Code!
4. #Devoxx #Javaslang @koenighotze Functors, applicatives, monads and friends stay home
5. #Devoxx #Javaslang @koenighotze Code that is easier to reason about
6. #Devoxx #Javaslang @koenighotze Side-effects are evil try { int i = 1/0; } catch (Throwable t) { … } Exceptions are goto-statements :(
7. #Devoxx #Javaslang @koenighotze Referential Transparency Math.random(); Math.max(1, 2); Math.random(); Math.max(1, 2); Pure functions are a Good ThingTm :(
8. #Devoxx #Javaslang @koenighotze Thinking in Values Immutability Performance Safety
9. #Devoxx #Javaslang @koenighotze In a nutshell, think about “what to code“ not “how to code”
10. #Devoxx #Javaslang @koenighotze Enter Java 8 (a) -> a + 2 list.stream().filter… Excitement…
11. #Devoxx #Javaslang @koenighotze “Try filtering all invalid users from a list of users”
12. #Devoxx #Javaslang @koenighotze Excitement?…until users.stream() .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
13. #Devoxx #Javaslang @koenighotze Painting by Gustav Courbet
14. #Devoxx #Javaslang @koenighotze import static javaslang.API.*; +
15. #Devoxx #Javaslang @koenighotze What we’ll cover Immutable collections Some functional sugar Pattern matching
16. #Devoxx #Javaslang @koenighotze Before we get to the details… Let’s fix that ugly code
17. #Devoxx #Javaslang @koenighotze Fixing Things…. users.stream() .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
18. #Devoxx #Javaslang @koenighotze Functional collections List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
19. #Devoxx #Javaslang @koenighotze No need for Collectors List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}) .collect(Collectors.toList());
20. #Devoxx #Javaslang @koenighotze No need for Collectors List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}); .collect(Collectors.toLis t());
21. #Devoxx #Javaslang @koenighotze Wrapping Exceptions List.ofAll(users) .filter(user -> { try { return user.validate(); } catch (Exception ex) { return false; }}); .collect(Collectors.toLis t());
22. #Devoxx #Javaslang @koenighotze Wrapping Exceptions List.ofAll(users) .filter(user -> Try.of(user::validateAddress) .getOrElse(false) ); } catch (IllegalStateException ex) { return ); .collect(Collectors.toList();
23. #Devoxx #Javaslang @koenighotze List.ofAll(users) List.filter(user -> Try.of(user::validateAddress) .getOrElse(false)); “Try filtering all invalid users from a list of users”
24. #Devoxx #Javaslang @koenighotze Immutable Collections Image by Douglas Muth, https://flic.kr/p/acFwxG
25. #Devoxx #Javaslang @koenighotze Mutable Collections are Evil Returning void == Side-Effect! interface Collection<E> { … void clear(); } interface Collection<E> { … void clear(); }
26. #Devoxx #Javaslang @koenighotze Easy solution? Collections Collections .unmodifiableList(list); .add("BUMM");
27. #Devoxx #Javaslang @koenighotze Easy solution? Collections Collections .unmodifiableList(list) .add("BUMM");
28. #Devoxx #Javaslang @koenighotze
29. #Devoxx #Javaslang @koenighotze Javaslang Collections List<~> t = List.of(“F95”); List<~> t2 = t.append(withName(“FCK”)); F95 / t
30. #Devoxx #Javaslang @koenighotze Immutable List<~> t = List.of(“F95”); List<~> t2 = t.prepend(“FCK”); F95 / t FCK t2
31. #Devoxx #Javaslang @koenighotze List<~> t = List.of(“F95”); List<~> t2 = t.prepend(“FCK”); F95 / FCK t t2 Persistent and Efficient
32. #Devoxx #Javaslang @koenighotze Streams are glorified Iterators Stream<String> jdk = Stream.of("a", “B"); jdk.map(String::toUpperCase); jdk.map(String::toLowerCase);
33. #Devoxx #Javaslang @koenighotze 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) at java.util.stream.ReferencePipeline$StatelessOp.<init>(ReferencePipeline.java :618) at java.util.stream.ReferencePipeline$3.<init>(ReferencePipeline.java:187) at java.util.stream.ReferencePipeline.map(ReferencePipeline.java:186)
34. #Devoxx #Javaslang @koenighotze Javaslang Streams Stream<String> slang = Stream.of("a", "B"); slang.map(String::toUpperCase); // “A”,“B” slang.map(String::toLowerCase); // “a”,“b”
35. #Devoxx #Javaslang @koenighotze Javaslang Streams Stream<String> slang = Stream.of("a", "B"); slang.map(String::toUpperCase) .take(2); slang.map(String::toLowerCase) .take(2);
36. #Devoxx #Javaslang @koenighotze Javaslang Streams Stream<String> slang = Stream.of("a", "B"); slang.map(String::toUpperCase) .take(2);// “A”,“B” slang.map(String::toLowerCase) .take(2);// “a”,“b”
37. #Devoxx #Javaslang @koenighotze Functional data structures improve performance and reduce the chance of unexpected behaviour
38. #Devoxx #Javaslang @koenighotze Functional Sugar
39. #Devoxx #Javaslang @koenighotze “Find a user and, if an address is available, fetch the user’s street”
40. #Devoxx #Javaslang @koenighotze Cascading Pile of Shame User user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
41. #Devoxx #Javaslang @koenighotze We’ve got java.util.Optional Optional<User> opt = Optional.ofNullable(user); if (optional.isPresent()) { … }
42. #Devoxx #Javaslang @koenighotze
43. #Devoxx #Javaslang @koenighotze Please stop using Optional#isPresent()
44. #Devoxx #Javaslang @koenighotze An Option is like a Gift Box None Some
45. #Devoxx #Javaslang @koenighotze Map opens the Gift Box Map Some Some ( )->
46. #Devoxx #Javaslang @koenighotze Nothing from Nothing ( )-> Map None None
47. #Devoxx #Javaslang @koenighotze Optional or Option? Optional
48. #Devoxx #Javaslang @koenighotze Optional or Option? Option Some None
49. #Devoxx #Javaslang @koenighotze Optional or Option? Option Some None Value Iterable
50. #Devoxx #Javaslang @koenighotze Optional or Option? Option Some None Value Iterable
51. #Devoxx #Javaslang @koenighotze Optional or Option? Option Some None Value Iterable Serializable
52. #Devoxx #Javaslang @koenighotze Fixing the Pile of Shame User user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
53. #Devoxx #Javaslang @koenighotze Option all the Things User user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
54. #Devoxx #Javaslang @koenighotze Option all the Things Option<User> user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
55. #Devoxx #Javaslang @koenighotze Option all the Things Option<User> user = repo.findOne("id"); if (user != null) { Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
56. #Devoxx #Javaslang @koenighotze Option all the Things 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()
57. #Devoxx #Javaslang @koenighotze Option all the Things Option<User> user = repo.findOne("id"); user.flatMap(User::getAddress) Address address = user.getAddress(); if (null != address) { return address.getStreet(); } }
58. #Devoxx #Javaslang @koenighotze Option all the Things Option<User> user = repo.findOne("id"); user.flatMap(User::getAddress) Address address = user.getAddress(); .map(Address::getStreet) return address.getStreet(); } }
59. #Devoxx #Javaslang @koenighotze repo.findOne("id") .flatMap(User::getAddress) .map(Address::getStreet) .getOrElse(""); “Find a user and, if an address is available, fetch the user’s street”
60. #Devoxx #Javaslang @koenighotze Option and map transform nested code into an understandable story
61. #Devoxx #Javaslang @koenighotze Working with legacy code Painting by Eero Järnefelt
62. #Devoxx #Javaslang @koenighotze Nice Validation Code public static String check(String iban){ if (validationMagic(iban)) { return iban; } throw new IllegalArgumentException(“Peng”); }
63. #Devoxx #Javaslang @koenighotze Awesome WTF Code String iban; try { iban = check("AL47"); } catch (IllegalArgumentException ex) { iban = ""; }
64. #Devoxx #Javaslang @koenighotze From Exceptions to Options String iban = lift(Iban::check) .apply("AL47...") .getOrElse("");
65. #Devoxx #Javaslang @koenighotze From Exceptions to Options String iban = lift(Iban::check) .apply("AL47...") .getOrElse("");
66. #Devoxx #Javaslang @koenighotze Wrapping Exceptions with Try Try.of(() -> stuffToDo())
67. #Devoxx #Javaslang @koenighotze Wrapping Exceptions with Try Failure Exception Success Result Try.of(() -> stuffToDo())
68. #Devoxx #Javaslang @koenighotze Exceptions to Options with Try Try.of(() -> check("AL..")) .getOrElse("")
69. #Devoxx #Javaslang @koenighotze Exceptions to Options with Try Try.of(() -> check("AL..")) .getOrElse("")
70. #Devoxx #Javaslang @koenighotze Lifting and Try-ing reduce exception handling clutter and side-effects
71. #Devoxx #Javaslang @koenighotze Structural Decomposition Image by Arend, https://flic.kr/p/pkBe4g
72. #Devoxx #Javaslang @koenighotze Classic HTTP Handling if (OK.equals(res.getStatusCode())) { return res.getBody(); } return emptyList();
73. #Devoxx #Javaslang @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
74. #Devoxx #Javaslang @koenighotze Pattern Matching Basics Match(expression) .of(cases)
75. #Devoxx #Javaslang @koenighotze Cases map functions to patterns Case(pattern, function)
76. #Devoxx #Javaslang @koenighotze Example Patterns $() wildcard pattern $(“foo”) equals pattern isIn(“a”, “b”) conditional pattern
77. #Devoxx #Javaslang @koenighotze HTTP Handling Fixed *Note: some type details missing Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 );
78. #Devoxx #Javaslang @koenighotze Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 ); HTTP Handling Fixed *Note: some type details missing OK or anything else
79. #Devoxx #Javaslang @koenighotze HTTP Handling Fixed *Note: some type details missing Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 );
80. #Devoxx #Javaslang @koenighotze HTTP Handling Fixed *Note: some type details missing Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 );
81. #Devoxx #Javaslang @koenighotze HTTP Handling Fixed Match(res.getStatusCode()) .of(
 Case($(OK), res.getBody()),
 Case($(), emptyList())
 ); *Note: some type details missing
82. #Devoxx #Javaslang @koenighotze Matching a Try public Try<…> fetchFromUrl(…) { … }
83. #Devoxx #Javaslang @koenighotze Matching a Try Match(fetchFromUrl(“…”)) .of( Case(Success($()), identity()), Case(Failure($()), emptyList()) );
84. #Devoxx #Javaslang @koenighotze Matching a Try Match(fetchFromUrl(“…”)) .of( Case(Success($()), identity()), Case(Failure($()), emptyList()) );
85. #Devoxx #Javaslang @koenighotze Matching a Try Match(fetchFromUrl(“…”)) .of( Case(Success($()), identity()), Case(Failure($()), emptyList()) );
86. #Devoxx #Javaslang @koenighotze Presto! Match(fetchFromUrl(“…”)) .of( Case(Success($()), identity()), Case(Failure($()), emptyList()) );
87. #Devoxx #Javaslang @koenighotze Pattern matching replaces complex if- then-else sequences with clear expressions
88. #Devoxx #Javaslang @koenighotze HashMap.of("Foo", "Bar", "Qux", "Baz") .bimap(String::toLowerCase, String::toUpperCase) .get("qux"); // BAZ Javaslang offers much more
89. #Devoxx #Javaslang @koenighotze Javaslang offers much more Tuple.of("Foo", 1) .map((s, i) -> Tuple.of(s + "Bar", i + 5)) // “FooBar”, 6
90. #Devoxx #Javaslang @koenighotze Javaslang offers much more
91. #Devoxx #Javaslang @koenighotze So, is this is the mother of all free lunches?
92. #Devoxx #Javaslang @koenighotze What are the drawbacks?
93. #Devoxx #Javaslang @koenighotze What are the drawbacks? count(Collection-libs) > count(Logging-libs)
94. #Devoxx #Javaslang @koenighotze What are the drawbacks? Option.of(foo) .map .filter .flatMap
95. #Devoxx #Javaslang @koenighotze Wrapping up Slick, stable, consistent API Object-functional Complex(?) Version 3 in 2017
96. #Devoxx #Javaslang @koenighotze .io http:// Do you want to know more?
97. #Devoxx #Javaslang @koenighotze Thank You! <david.schmitz@senacor.com>