Polyglot Plugin Programming
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  • 1. 1
  • 2. Polyglot Plugin DevelopmentHow to write plugins in a language other than JavaStefan SaasenConfluence Team Lead, Atlassian 2
  • 3. Audience• Written an Atlassian plugin in Java• Interested in other programming languages• Eager to see what is possible with Atlassian plugins 3
  • 4. Show of hands• Who has actually written a Atlassian plugin?• In any other language than Java? 4
  • 5. 5
  • 6. Rhino 6
  • 7. 7
  • 8. https://bitbucket.org/ssaasen/atlassian-jruby-example-pluginhttps://bitbucket.org/ssaasen/atlassian-scala-example-plugin 8
  • 9. Polyglot Plugins• Why?• How? • Example 1: Scala • Example 2: JRuby• Go and do it! 9
  • 10. Why not? 10
  • 11. Why ? 11
  • 12. What to tell the boss?• Leverage existing knowledge in the team• Libraries/applications already written in language X• Time to market/devspeed• Explore technologies in a sandboxed environment• Grass looks always greener on the other side 12
  • 13. What to tell the boss?• Leverage existing knowledge in the team• Libraries/applications already written in language X• Time to market/devspeed• Explore technologies in a sandboxed environment• Grass looks always greener on the other side 13
  • 14. 14
  • 15. “No time to write in Java” “Less bugs”“Succinctness” 15
  • 16. 16
  • 17. Polyglot Plugins• Why?• How? • Example 1: Scala • Example 2: JRuby• Go and do it! 17
  • 18. • Hybrid language: Object oriented & functional• Concise, statically typed (with type inference)• Higher order/first class functions, pattern matching• Powerful type system• Rich standard library 18
  • 19. 19
  • 20. 20
  • 21. 21
  • 22. 22
  • 23. How? 23
  • 24. Overview Scala scalac Scala Runtime LibraryJava Bytecode *.class Java Java Standard Library javac JVM 24
  • 25. 25
  • 26. 26
  • 27. Build process• Start with Maven to get the AMPS goodness• Use the maven-scala- plugin• Add SBT if necessary 27
  • 28. Build process f. • Compile time is a concern! • FSC • Useful Maven goals: mvn scala:cc mvn scala:console 28
  • 29. Bundle runtime 29
  • 30. Size might be a problem :( 30
  • 31. Deployment options Option Scope Package Size mvn package Bundle compile -Pbundle 8.5 MB SimpleBundle & Shrink mvn package Deploy compile 680 KB w/ProGuard -Pproduction externally DeployInstall separately provided mvn package 50 KB internally 31
  • 32. Simply install using the plugin manager! 32
  • 33. Development checklist• Dependencies: Scala libraries are jar files and often available from Maven repositories• Compile time: mvn scala:cc for continuous compilation• Workflow: scala:cc & atlas-cli pi or mvn package && atlas-install-plugin• Profit: mvn scala:console to get the Scala REPL 33
  • 34. Scala: Workingwith Java APIs 34
  • 35. Scala gotchas (the 80%)• Collections• Method naming conventions• Annotations• Null vs. Option 35
  • 36. Collections • Immutable vs Mutable, serial vs. parallel • Rich API: Prefer Scala collections • Convert between Java and Scala collections when calling Java methods • Solution: JavaConverters (explicit, preferred) vs. JavaConversions (implicit) • Watch out for serialization: Bandana/XStream 36
  • 37. 37
  • 38. 38
  • 39. 39
  • 40. Method naming conventions• Libraries rely on bean style naming conventions e.g. XWork, Velocity• Scala: uniform access principle• Solution: Use @BeanProperty and @BooleanBeanProperty 40
  • 41. 41
  • 42. 42
  • 43. 43
  • 44. (Meta)-Annotations• How to use @JavaAnnotation on a getter method when defining fields?• Scala meta annotations @beanGetter, @beanGetter, @field, @getter, @setter 44
  • 45. 45
  • 46. 46
  • 47. 47
  • 48. Option vs. null • In Scala Option represents an optional value. • Don’t let the billion-dollar mistake leak into your Scala code! • Solution: wrap nullable method calls in an Option 48
  • 49. 49
  • 50. 50
  • 51. 51
  • 52. 52
  • 53. Show me the code! 53
  • 54. 57
  • 55. 58
  • 56. 59
  • 57. 60
  • 58. Example Scala plugin• Servlet & XWork action• Confluence macro• REST via Jersey/Jackson• Build setup• Use as a starting point https://bitbucket.org/ssaasen/atlassian-scala-example-plugin 61
  • 59. Let’s recap • Replace Java entirely with Scala or mix and match • Runtime library: 3 deployment options • Fits into the AMPS development workflow • Scala Gotchas: watch out for common problems • “Scala is a great fit to write Atlassian plugins in” 62
  • 60. Agenda• Why?• How? • Example 1: Scala • Example 2: JRuby• Go and do it! 63
  • 61. (J)Ruby• Dynamic, object-oriented language• Everything is an object (no “primitives”)• Meta-programming and open, executable classes allow for easy creation of DSLs• JRuby: Ruby runtime written in Java 64
  • 62. 65
  • 63. How? 66
  • 64. Overview RubyRuby files *.rb Your Ruby Standard RubyGems jrubyc Code Library Ruby RuntimeJava Bytecode *.class Java Java Standard Library javac JVM 67
  • 65. 68
  • 66. 69
  • 67. 70
  • 68. Plugins can’t bewritten in Ruby 71
  • 69. But we can still use Ruby in a plugin! 72
  • 70. Recipe for using JRuby• Embed the Ruby Runtime• Use Java to execute Ruby scripts and classes• Make components of the host application available• Use the script execution result in Java 73
  • 71. Embedding Strategies• javax.scripting - JSR 223• Apache Bean Scripting Framework (BSF)• JRuby Embed - lower level JRuby API 74
  • 72. Embedding Strategies• javax.scripting - JSR 223 Only configurable via system properties :(• Apache Bean scripting framework (BSF) No point in adding a separate API• JRuby Embed - lower level JRuby API 75
  • 73. 76
  • 74. Building the plugin• Package Ruby files• Download and package Ruby gems• Make Ruby gems available on the Ruby LOAD_PATH• Bundle everything into a plugin jar file• A lot of Maven XML :)• Caveat: JRuby runtime is even larger! 77
  • 75. Show me the code! 78
  • 76. 79
  • 77. 80
  • 78. 1 minute 81
  • 79. 82
  • 80. 83
  • 81. 84
  • 82. 85
  • 83. 86
  • 84. 87
  • 85. 88
  • 86. 89
  • 87. Example JRuby plugin• How to use Rubygem based libraries in a plugin• How to access host components in Ruby• How to use the execution result• Sinatra in Confluence ;-) https://bitbucket.org/ssaasen/atlassian-jruby-example-plugin 90
  • 88. Let’s recap• The plugin can’t be written in Ruby!• Use the Ruby runtime• Development workflow bonus: dynamic reloading!• The overhead of adding the runtime and providing Java glue code makes this only feasible for high value use cases :( 91
  • 89. Conclusion• Scala is a great alternative when developing an Atlassian plugin• JRuby is powerful, makes developing in a dynamic language possible but requires more work and custom Java adapter code• Java interoperability needs to be well understood in both cases 92
  • 90. TAKE-AWAYS“ The power of the Atlassian plugin framework allows you to build your plugins the way you want and ” Java doesn’t have to be the limit. #atlascamp 93
  • 91. Thank you! 94
  • 92. • “Happy Foods” by swanksalot http://www.flickr.com/photos/swanksalot/5021262869/• “Construction” by Daniel Morris http://www.flickr.com/photos/danielmorris/275438405/• “70 80 90” by roujo http://www.flickr.com/photos/tekmagika/437989361 95