Whoops! Where did my architecture go?

Slides of my talk @ SpringOne2GX 2012

Transcript

1. Whoops! Where did my architecture go? Oliver Gierke, Senior Member Technical Staff ogierke@vmware.com - @olivergierke © 2012 SpringOne 2GX. All rights reserved. Do not distribute without permission.
2. 2 Oliver Gierke Spring Source engineer Project lead Core/JPA/MongoDB ogierke@vmware.com 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