Whoops! Where did my architecture go?

Slides of my talk at Java User Group Berlin/Brandenburg, June 2012

Transcript

1. Whoops! Where did my architecture go? Approaches to architecture management for Java and Spring applications Oliver Gierke
2. Oliver Gierke SpringSource Engineer Spring Data ogierke@vmware.com olivergierke www.olivergierke.de
3. Background 5 years of consulting Lots of code reviews Eoin Woods‘ talk on InfoQ
4. Roadmap Architecture 101 A plain Java based approach Hera
5. The 3 C' of Architecture Constraints Complexity Change © Uwe Friedrichsen
6. The 2 C's of Architecture Complexity Change
7. Architecture 101
8. Know your dependencies
9. Granularity Modules Layers Vertical slices Subsystems
10. Granularity Java ARchive Package Class
11. Of layers and slices…
14. Presentation Service Data Access
15. Presentation Service Data Access
16. Presentation Service Data Access
17. Presentation Service Data Access Account Customer Core
18. Presentation Service Data Access Account Customer Core
19. Presentation Service Data Access Account Customer Core
20. Layers Well understood Known to developers Less important to business
21. Slices Hardly understood New to developers Key for business req
22. Presentation Service Data Access Account Customer Core
23. "How to implement an architecture inside a codebase?
24. Architecture VS. Codebase
25. "How to implement an architecture inside a codebase?
26. "How to implement an architecture inside a codebase?
27. "How to enforce an architecture inside a codebase?
28. Code analysis JDepend Sonar
29. Demo
30. Sonargraph Formerly known as SonarJ
31. Demo
32. A plain Java based approach
33. "How far can we get with plain Java means only?
34. Presentation Service Data Access Account Customer Core
35. Packages
36. …. layer.slice ? …. slice.layer ? … slice ?
37. …domain.core …service.core …repository.core
38. …core.domain …core.service …core.repository
39. … core … customer … account
40. Layers first Leaks slice internals Lower layers visible to everyone
41. Slices first/only Start with package per slice Expose interfaces and domain types Keep implementations private
42. Slices first/only Encapsulates business module Internals understood anyway
43. "Start with less packages and the least visibility possible…
44. Presentation Service Data Access Account Customer Core
45. Presentation Service Data Access Account Customer Core
46. Subsystems
47. Background Risk management at German public bank Quite a few other SpringSource clients
48. Systems grow big!
49. Remember the 2 C's?
50. Complexity & Change
51. "How to localize change?
52. "Separate frequent from infrequent change!
53. Granularity Class Package Java ARchive
54. Host
55. Host SPI SPI SPI
56. Host SPI SPI SPI Plugin Plugin
57. Host SPI SPI SPI Plugin Plugin
58. Host SPI SPI SPI Plugin Plugin
59. Context No OSGi Spring based Build-time composition Don‘t touch the host system
60. Host
61. Host Plugin Plugin
62. Host Plugin Plugin App
63. "How to make the host aware of the plugins?
64. "How to dynamically collect Spring beans of a given type?
65. classpath*:META-INF/ spring/plugin-context.xml
66. Host
67. Host SPI SPI SPI
68. Host SPI SPI SPI Plugin Plugin
69. Host SPI SPI SPI Plugin Plugin
70. Host SPI SPI SPI Plugin Plugin
71. classpath*:META-INF/ spring/plugin-context.xml SPI SPI SPI META-INF/ spring/plugin- context.xml META-INF/ spring/plugin- context.xml
72. @Component public class MyComponentImpl implements TransferService { private List<MyPlugin> plugins; @Autowired public MyComponentImpl(List<MyPlugin> plugins) { this.plugins = plugins; } … } public interface MyPlugin { void doSomething(); }
73. Demo
74. XML? Back in the days
75. (XML?) Back in the days Probably not a big deal anymore
76. Easy access?
77. @Component public class MyComponentImpl implements TransferService { private List<MyPlugin> plugins; @Autowired public MyComponentImpl(List<MyPlugin> plugins) { this.plugins = plugins; } … } public interface MyPlugin { void doSomething(); }
78. @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? } }
79. Spring Plugin
80. "The smallest plugin system ever!
81. Plugins Selection criterion Callback method Let the implementation decide
82. Registry Equipped with plugins Common access patterns
83. 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); … }
84. @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(); }
85. @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()); } }
86. OrderAware PluginRegistry Respects @Order/Ordered OAPR.reverse()
87. Bells‘n‘whistles FactoryBean Spring namespace Lazy-eval
88. Spring Plugin github.com/SpringSource/spring-plugin Apache 2.0
89. Spring Integration2
90. <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" />
91. Demo
92. Take-aways Know your dependencies On every granularity Start as strict as possible Get lenient where necessary
93. Thanks & credits Eoin Woods - Talk @ InfoQ Uwe Friedrichsen - Slides @ Slideshare
94. Resources Spring Data JPA @ GitHub Sonargraph Spring Plugin