Building APIs with Kotlin and Spark
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This presentation explains how to use the Spark framework together with the Kotlin programming language and the JVM to build robust APIs. The presentation begins with some basics about the Kotlin language from JetBrains. It then gives a brief introduction to Spark, a Sinatra-inspired framework for setting up Web routes. It concludes with some references to three blog posts with more explanation and a GitHub repository where the sample code can be found.
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Building APIs with Kotlin and Spark
- 1. Building APIs with Kotlin and Spark By Travis Spencer (@travisspencer)
- 2. Intro & Agenda • Why Kotlin • Some basics of the syntax • Quick intro to Spark • Using Kotlin & Spark together @travisspencer / @nordicapis
- 3. Why Kotlin • Compiles to JVM bytecode and JavaScript • From industry not academia • Open source & costs nothing to adopt • Can use existing Java or JavaScript frameworks • Very low learning curve @travisspencer / @nordicapis
- 4. Why Kotlin • Supports OO and functional programming styles • Excellent IDE support (Intellij and Eclipse) • Perfect for Java & Android shops • Strong commercial support from @travisspencer / @nordicapis
- 5. • fun keyword Basic Syntax @travisspencer / @nordicapis
- 6. • fun keyword • Return type (Unit default) Basic Syntax @travisspencer / @nordicapis
- 7. • fun keyword • Return type (Unit default) • Types of args after names Basic Syntax @travisspencer / @nordicapis
- 8. • fun keyword • Return type (Unit default) • Types of args after names Basic Syntax @travisspencer / @nordicapis • Named arguments
- 9. • fun keyword • Return type (Unit default) • Types of args after names Basic Syntax @travisspencer / @nordicapis • Named arguments • Single expression functions
- 10. Passing Function Literals Call like this… …instead of this! @travisspencer / @nordicapis
- 11. • Allows you to pass any type that inherits from Controllable • Safely upcast at run-time Declaration-site Variance @travisspencer / @nordicapis
- 12. • Variables must be declared as nullable • Null checks are required at compile time Nullability Must be Explicit @travisspencer / @nordicapis
- 13. Data Classes • equals • hashCode • toString • copy • Getters and setters @travisspencer / @nordicapis
- 14. Multiple Return Values @travisspencer / @nordicapis
- 15. Overridable Methods @travisspencer / @nordicapis
- 16. Overriding Open Methods • Override @travisspencer / @nordicapis
- 17. Controller Overloads • Override • Named arguments (again) @travisspencer / @nordicapis
- 18. Controller Overloads • Override • Named arguments (again) • mapOf standard function @travisspencer / @nordicapis
- 19. Controller Overloads • Override • Named arguments (again) • mapOf standard function • to keyword to nicely define associative array @travisspencer / @nordicapis
- 20. Smartcasts Is of type Any! @travisspencer / @nordicapis
- 21. Smartcasts is operator checks if type is ControllerResult at run-time @travisspencer / @nordicapis
- 22. Smartcasts ControllerResult properties are available after logical AND @travisspencer / @nordicapis
- 24. String Interpolation @travisspencer / @nordicapis
- 26. val l = b?.length() ?: -1 Elvis Operator
- 27. Extension Functions Adds foo() to all strings @travisspencer / @nordicapis
- 28. And of course equality is done right! Equals @travisspencer / @nordicapis
- 29. • Conversion tools built into Intellij & Eclipse • Maven, Ant, Gradle • Docs with Javadoc and Markdown • …and Tools @travisspencer / @nordicapis
- 30. A Debugger! @travisspencer / @nordicapis
- 32. Intro to Spark • Tiny framework for setting up routes • No XML config • No annotations • Starts a Web server automatically • sparkjava.com
- 33. Hello World Then hit http://localhost:4567/hello
- 34. Request & Response Classes Request & Response objects have lots of useful methods
- 36. Parameterized URL Patterns http://localhost:4567/users/bob bob == :name parameter defined in route
- 38. Building a Robust API with Spark Controllers, Dependency Injection, etc.
- 39. Code Walkthrough
- 40. • Intro to Spark - http://goo.gl/oPm0jV • Kotlin + Spark blog post • Part 1 - http://goo.gl/WlxKQq • Part 2 - http://goo.gl/cE0gxz • Source code - http://goo.gl/x1CVuc Links to More Info
Editor's Notes
- fun keyword Return type – Unit Types of args after names Named arguments Single expression functions
- fun keyword Return type – Unit Types of args after names Named arguments Single expression functions
- fun keyword Return type – Unit Types of args after names Named arguments Single expression functions
- fun keyword Return type – Unit Types of args after names Named arguments Single expression functions
- fun keyword Return type – Unit Types of args after names Named arguments Single expression functions
- main.kt application.kt Takes a composer Router.routeTo Composable interface ContainerComposer.kt Router.kt routeTo Router (wrapped in clousure) Controllable.kt routeTo (reflection) Example controllers