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Java to scala

Java to scala



Graham Tackley discusses Scala adoption at the Guardian

Graham Tackley discusses Scala adoption at the Guardian



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Java to scala Java to scala Presentation Transcript

  • (mostly)How we moved from ^ Java to Scala Graham Tackley guardian.co.uk
  • History• Java shop since 2006• guardian.co.uk: java + spring + velocity + hibernate + oracle• ~100k lines production java code (and ~35k xml...)
  • Content API• Provide API to access all of our website content• Limited beta released early 2009• Started implementation of final version late 2009• Live May 2010: http://content.guardianapis.com
  • Content API(demo of http://content.guardianapis.com)
  • November 2009• Started new Content API implementation• java + guice + guice servlets + apache solr
  • November 2009• A few people had played with scala• No production scala code
  • January 2010• Comprehensive integration tests were very important to us• Started writing our integration tests in Scala with the awesome ScalaTest• Already a maven project, so mixed scala- java support easy with maven-scala-plugin demo: mavan-scala-plugin, ScalaTest
  • January 2010
  • January 2010• A fair bit of our test code was java- without-semicolons as we learnt about Scala...
  • January 2010
  • February 2010• ... despite that we loved it so much that after a month we decided to convert the whole app to Scala• scala + guice + guice servlets + apache solr
  • Our top 5 things we loved about scala on day one
  • 1. Sensible Class Constructors =>
  • 1. Sensible Class Constructors
  • 2. Type inference / val & varArrayList<String> myList = new ArrayList<String>(); =>val myList = new ArrayList[String]
  • 3. No source file naming constraints• Don’t need to be named after package & class name like java• So multiple classes are allowed in a single file e.g. ResponseRenderer.scala
  • 4. REPL (console)• run “scala” for a scala shell• awesome for experimentation
  • 5. Same tools, libs, deployment & runtime characteristics as Java• We still use IntelliJ (with the scala plugin)• A scala war file is just a war file• All the experience of running jvm in production still applies• Can still use java libraries e.g. GuiceServletConfig.scala, XmlFormatter.scala
  • Our top 5 things we loved about scala on day one SUMMARY:Scala is great even if you only use it as a more concise java (java-without-semicolons™); for us this was a great way to start.
  • July 2010• Switched from maven to simple-build-tool• Mainly for incremental compilation• ~ test-quick and ~ prepare-webapp also invaluable
  • Writing codeone year on
  • some early code...it took us a while to realise that most of the loops we wrote in Java were actually “map” or “flatMap”
  • ... ended up asit took us a while to realise that most of the loops we wrote in Java were actually “map” or “flatMap”
  • Summary• Migration path from Java relatively smooth• Take it easy, and don’t fear java-without- semicolons in the early days• An incremental embrace of Scala features worked really well for us• Hide the Java yuk with implicit conversions
  • • http://content.guardianapis.com• http://www.guardian.co.uk/open-platform• http://github.com/guardian/open-platform- content-api-scala-client graham.tackley@guardian.co.uk ■ @tackers