Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Java to scala

6,219 views

Published on

How we (partly) moved from Java to Scala. Talk at Scala Lift Off 7 Oct 2010

Published in: Technology
  • Follow the link, new dating source: ♥♥♥ http://bit.ly/2u6xbL5 ♥♥♥
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • Dating direct: ♥♥♥ http://bit.ly/2u6xbL5 ♥♥♥
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here

Java to scala

  1. 1. (partly) How we moved from ^ Java to Scala Graham Tackley guardian.co.uk
  2. 2. History • Java shop since 2006 • guardian.co.uk: java + spring + velocity + hibernate + oracle • ~100k lines production java code (and ~35k xml...)
  3. 3. Content API • Provide API to access all of our website content • Limited beta released early 2009 • Started implementation of final version late 2009 • Live April 2010: http://content.guardianapis.com
  4. 4. December 2009 • Started new Content API implementation • java + guice + guice servlets + apache solr
  5. 5. December 2009 • A few people had played with scala • No production scala code
  6. 6. 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
  7. 7. January 2010
  8. 8. January 2010 • A fair bit of our test code was java- without-semicolons as we learnt about Scala...
  9. 9. January 2010
  10. 10. 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
  11. 11. February 2010 Still some very java-like code...
  12. 12. February 2010 ... immediate win with non-IDE generated constructors ...
  13. 13. February 2010 ... and some things much more readable than Java
  14. 14. July 2010 • Switched from maven to simple-build-tool • Mainly for incremental compilation • ~ test-quick and ~ prepare-webapp also invaluable
  15. 15. Feb-Oct 2010 • Much learning within the team as to how to write concise, readable Scala code
  16. 16. Option or How we learned to stop worrying and love the Option We’d read “don’t use nulls, use Option instead” DAY ONE s/x == null/x.isDefined DAY THREE x match { case None => ... case Some(value) => ... }
  17. 17. Option or How we learned to stop worrying and love the Option WEEK THREE TODAY We now think of Options as lists with zero or one entries
  18. 18. map & flatMap it took us a while to realise that most of the loops we wrote in Java were actually “map” or “flatMap”
  19. 19. Java Libraries Content API extensively uses Solr/J, which is good but returns loads of nulls And don’t get me started on HttpServletRequest... We used implicit conversions to hide the Java yuk
  20. 20. 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
  21. 21. • http://content.guardianapis.com • http://www.guardian.co.uk/open-platform • http://github.com/guardian/open-platform- content-api-scala-client • http://blog.tackley.net graham.tackley@guardian.co.uk

×