Whoops! Where did my architecture go?

Transcript

1. Whoops! Where did my architecture go? Oliver Gierke, Senior Member

   Technical Staff [email protected] - @olivergierke © 2012 SpringOne 2GX. All rights reserved. Do not distribute without permission.

2. 2 Oliver Gierke Spring Source engineer Project lead Core/JPA/MongoDB [email protected]

   www.olivergierke.de olivergierke

3. 3 Spring Data Modern Data Access For Enterprise Java NoSQL

   JPA JDBC Redis Big Data Hadoop HBase MongoDB Neo4j REST exporter Roo Hive Pig Querydsl Repositories 1 free copy per attendee! Gemfire Splunk

4. 4 Background 5 years of consulting Lots of code reviews

   Eoin Woods‘ talk on InfoQ

5. Roadmap Architecture 101 A plain Java based approach Spring Plugin

   5

6. The 3 C' of Architecture Constraints Complexity Change 6

7. The 2 C' of Architecture 7 Complexity Change

8. Architecture 101 8

9. Know your dependencies 9

10. Granularity Modules Layers Vertical slices Subsystems 10

11. Granularity Java ARchive Package Class 11

12. Of layers and slices… 12

13. Presentation Service Data Access Account Customer Core 13

14. 14 Layers Well understood Known to developers Less important to

    business

15. Slices Hardly understood New to developers Key for business req

    15

16. Presentation Service Data Access Account Customer Core 16

17. 17 "How to implement an architecture inside a codebase?

18. Architecture VS. Codebase 18

19. 19 "How to implement an architecture inside a codebase?

20. 20 "How to enforce an architecture inside a codebase?

21. Code analysis JDepend Sonar 21

22. Demo 22

23. Sonargraph Formerly known as SonarJ 23

24. Demo 24

25. A plain Java based approach 25

26. 26 "How far can we get with plain Java means

    only?

27. Presentation Service Data Access Account Customer Core 27

28. 28 Packages

29. 29 …. layer.slice ? …. slice.layer ? … slice ?

30. 30 …web.core …service.core …repository.core

31. 31 …core.web …core.service …core.repository

32. 32 … core … customer … account

33. Layers first 33 Leaks slice internals Lower layers visible to

    everyone

34. Slices first/only Start with package per slice Expose interfaces and

    domain types Keep implementations private 34

35. Slices first/only Encapsulates business module Internals understood anyway 35

36. 36 "Start with less packages and the least visibility possible…

37. Presentation Service Data Access Account Customer Core 37

38. Presentation Service Data Access Account Customer Core 38

39. Subsystems 39

40. Background 40 Risk management at German public bank Quite a

    few other SpringSource clients

41. Systems grow big! 41

42. Remember the 2 C's? 42

43. Complexity & Change 43

44. 44 "How to localize change?

45. 45 "Separate frequent from infrequent change!

46. 46 Granularity Class Package Java ARchive

47. Host SPI SPI SPI Plugin Plugin 47

48. 48 Context No OSGi Spring based Build-time composition Don‘t touch

    the host system

49. Host Plugin Plugin App 49

50. 50 "How to make the host aware of the plugins?

51. 51 "How to dynamically collect Spring beans of a given

    type?

52. 52 classpath*:META-INF/ spring/plugin-context.xml

53. Host SPI SPI SPI Plugin Plugin 53

54. classpath*:META-INF/ spring/plugin-context.xml SPI SPI SPI META-INF/ spring/plugin- context.xml META-INF/ spring/plugin-

    context.xml 54

55. @Component public class MyComponentImpl implements TransferService { private List<MyPlugin> plugins;

    @Autowired public MyComponentImpl(List<MyPlugin> plugins) { this.plugins = plugins; } … } public interface MyPlugin { void doSomething(); } 55

56. Demo 56

57. XML? 57 Back in the days

58. (XML?) Back in the days Probably not a big deal

    anymore 58

59. Easy access? 59

60. @Component public class MyComponentImpl implements TransferService { private List<MyPlugin> plugins;

    @Autowired public MyComponentImpl(List<MyPlugin> plugins) { this.plugins = plugins; } … } public interface MyPlugin { void doSomething(); } 60

61. @Component public class MyComponentImpl implements TransferService { // Constructor omitted

    public Result myMethod(SomeParameter parameter) { // Select the first one to match to invoke? // Select multiple ones to invoke? // Select and fallback to one if none found? // Select and throw an exception if none found? } } 61

62. 62 Spring Plugin

63. 63 "The smallest plugin system ever!

64. 64 Plugins Selection criterion Callback method Let the implementation decide

65. Registry Equipped with plugins Common access patterns 65

66. public interface Plugin<T> { public boolean supports(T delimiter ); }

    public interface PluginRegistry<S extends Plugin<T>, T> { T getPluginFor(S delimiter); T getPluginFor(S delimiter, T default); <E extends Exception> T getPluginFor(S del, E e) throws E; List<T> getPluginsFor(S delimiter); … } 66

67. @Component public class MyComponentImpl implements TransferService { private PluginRegistry<MyPlugin, String>

    plugins; @Autowired public MyComponentImpl(PluginRegistry<MyPlugin, String> plugins) { this.plugins = plugins; } } public interface MyPlugin extends Plugin<String> { void doSomething(); } 67

68. @Component public class MyComponentImpl implements TransferService { private final MyPlugin

    defaultPlugin = new MyDefaultPlugin(); public Result myMethod(String parameter) { // Select the first one to match to invoke? … = plugins.getPluginFor(parameter); // Select multiple ones to invoke? … = plugins.getPluginsFor(parameter); // Select and fallback to one if none found? … = plugins.getPluginFor(parameter, defaultPlugin); // Select and throw an exception if none found? … = plugins.getPluginsFor(parameter, new RuntimeException()); } } 68

69. 69 OrderAware PluginRegistry Respects @Order/Ordered OAPR.reverse()

70. Bells‘n‘whistles FactoryBean Spring namespace Lazy-eval 70

71. Spring Plugin 71

72. Spring Integration2 72

73. <bean class="….FirstSamplePlugin" /> <bean class="….SecondSamplePlugin" /> <int:channel id="input" /> <int:channel

    id="output" /> <int-plugin:dynamic-service-activator input-channel="input" outputChannel="output" plugin-type= "….MyPlugin" method= "myBusinessMethod" delimiter="payload" invocation-arguments= "payload" /> 73

74. Demo 74

75. Take-aways 75 Know your dependencies On every granularity Start as

    strict as possible Get lenient where necessary

76. Thanks & credits Eoin Woods - Talk @ InfoQ Uwe

    Friedrichsen - Slides @ Slideshare 76

77. Resources Spring Data JPA @ GitHub Sonargraph Spring Plugin Whoops

    sample code 77