Funció

So if you want more Scala at BCN Dev Con, go vote your favorite papers!

Jordi and Ignasi introducing Scala to newbies at MOB on Sept. 27th

Open the project in IntelliJ and... have fun!

New [Barcelona Scala Developers meetup](http://www.meetup.com/Scala-Developers-Barcelona/) on Wednesday 27 of february at [Itnig](http://itnig.net/en/office)! As you may already know, we, the guys behind funció and [agilogy](http://www.agilogy.com), are also the organizers of the [Barcelona Scala Developers meetup](http://www.meetup.com/Scala-Developers-Barcelona/). We recently reached 50 members and it is high time we meet again to talk about Scala, program in Scala and have a Scala beer! In this talk we ([Jordi Pradel](https://twitter.com/agile_jordi) and [Jose Raya](https://twitter.com/_joseraya)) will develop a little application using JAX-RS, the Java standard for developing RESTful applications, in Scala. And we want to develop it live and from scratch. Attendees will be invited to participate by pair programming with us, asking questions, contributing opinions... How will we do it? Well, of course, in a 100% functional style *and* using agile techniques (like Test Driven Development and Behavior Driven Development). After all, we are agilogy + funció and this is our agile functional style. Many, many thanks to the people at [Itnig](http://itnig.net/en), who will be hosting the event at their wonderful office. And thanks to [Moritz](http://www.moritz.com/) for the beers. Didn't I told you? If you are thirsty, you can grab some beers. ## Information: - **Language?** English. - Spanish or Catalan if everybody understands them - **When?** Wednesday, February, 27 - **Timing?** From 19.00h to 20.30h - **Register** at the [Meetup event](http://www.meetup.com/Scala-Developers-Barcelona/events/105165802/) - **Where?** itnig HQ office: - Carrer Àlaba 61, 5è 2a (08005 Barcelona) - http://itnig.net/en/office ## Collaborators:  [Barcelona Scala Developers meetup](http://www.meetup.com/Scala-Developers-Barcelona/)  [funció](http://func.io)  [agilogy](http://www.agilogy.com)  [Itnig](http://itnig.net/en)

These days I've been studying different alternatives to implement a REST API in Scala. I had used an almost framework-free approach in a previous project, but this time I had some specific requirements in mind: - I want to be able to discover the API using reflection, so that (eventually) an API documentation can be generated automatically. I'm thinking [Swagger](http://swagger.wordnik.com/). - I want to avoid using unmature frameworks. - I want to avoid using frameworks that abuse Scala operators (what I'd call *emoticonic* frameworks with operaturs such as :>:). - I want top Java interoperability. Being able to easily write some methods or resources in the API in plain old Java is interesting, even if I think we won't need to do so. - I want to be able to do Dependency Injection by hand. I would like to avoid adding Guice or Spring to the mix... until they really pay off (if and when they do). - In general, I want the solution to be as simple as possible. I finally came across a combination that may suit (almost all of) my needs: - Scala 2.9.2 - [Jersey 1.2](http://jersey.java.net/) as the [JAX-RS](http://jax-rs-spec.java.net/) implementation - [Jackson 1.9.5](http://wiki.fasterxml.com/JacksonHome) and [Jackson module Scala 1.9.3](http://wiki.fasterxml.com/JacksonModuleScala) for Scala JSON serialization and deserialization - A [Jetty server](http://jetty.codehaus.org/jetty/) 8.1.0-RC5 to run it - Finally, I did some integration tests using [Scalatest](http://www.scalatest.org/) and [Apache HTTPComponents HTTPClient](http://hc.apache.org/httpcomponents-client-ga/index.html) Check it out here: https://bitbucket.org/jordipradel/jersey-scala-example Ok... in fact, I found some glitches: - Jackson Module Scala can't skip fields with value None when serializing to JSON: It creates a JSON field with null value. Interestingly enough, it works perfectly well the other way arround: Not providing a field in a JSON object is correctly deserialized to None if the Scala property is of type Option. - JSON serialization has been not that simple to configure. And there are many things that still need more exploration: - Error handling using exception mappers - Specifically, JSON deserialization error handling so that we can provide infromative messages about what's wrong with the JSON we receive ## Alternatives Some discarded alternatives were: - [Jerkson](https://github.com/codahale/jerkson): Another Jackson base Scala JSON library... now abandoned. - Scala 2.10.0-RC2: That version didn't play well with Jackson. That is: java.lang.NoSuchMethodError: scala.Predef$.augmentString(Ljava/lang/String;)Lscala/collection/immutable/StringOps Some alternatives I didn't try: - [Jacks](https://github.com/wg/jacks) yet another Jackson based Scala JSON library - [Spray](http://spray.io/) whichs seems a nice alternative... althought I'm not sure how easy it would be to discover the api at runtime and to mix Java and Scala. - [Play! framework](http://www.playframework.org/) which seems more oriented towards application development (with its views, DB layer, etc) - [Lift](http://liftweb.net/): It seems to use pattern matching for URL routing, and that seems difficult to discover using introspection, to say the least. - [Blueeyes](https://github.com/jdegoes/blueeyes), [Pinky](https://github.com/pk11/pinky/wiki) and others

You may probably already know about [BDD](http://en.wikipedia.org/wiki/Behavior-driven_development) and [Cucumber](http://cukes.info/). Well, Cucumber allows you to program the steps in your scenario in Ruby... and now in Java and Scala, too. Therefore, I evaluated Cucumber as a BDD solution for an upcoming Scala project. And it did really well, compared to other solutions that were quite more difficult to set up. This post is almost unnecessary. It is that easy. But, just in case you are unsure what versions to use, or how to do it, here you have a quick recipe. If you want the complete picture, check the example project I just created at Bitbucket: https://bitbucket.org/jordipradel/cucumber-scala-example . ## Ingredients - [SBT 0.12.1](http://www.scala-sbt.org/) - [Cucumber SBT plugin 0.7.0](https://github.com/skipoleschris/cucumber-sbt-plugin) - Scala 2.10.0-RC2 - [Scalatest 2.0.M5](http://www.scalatest.org/): Totally optional, use your preferred asserts! ## Directions 1. Add the SBT Cucumber plguin to your project (file project/build.sbt): resolvers += "Templemore Repository" at "http://templemore.co.uk/repo/" addSbtPlugin("templemore" % "sbt-cucumber-plugin" % "0.7.0") 2. Add Scala version, Scalatest dependency and SBT Cucumber plugin default settings to your project (file build.sbt): scalaVersion := "2.10.0-RC2" libraryDependencies += "org.scalatest" % "scalatest_2.10.0-RC2" % "2.0.M5" % "test" seq(cucumberSettings : _*) 3. Create your feature (e.g. a file Multiplication.feature in src/test/resources/bdd): Feature: Multiplication In order to avoid making mistakes As a dummy I want to multiply numbers Scenario: Multiply two variables Given a variable x with value 2 And a variable y with value 3 When I multiply x * y Then I get 6 4. Create a Scala steps definition class (e.g. in src/test/bdd/MultiplicationSteps.scala): package bdd import cucumber.api.scala.{ScalaDsl, EN} import org.scalatest.matchers.ShouldMatchers import scala.collection.mutable.{Map => MutableMap} class MultiplicationSteps extends ScalaDsl with EN with ShouldMatchers { val vars = MutableMap[String,Int]() var result = 0 Given("""^a variable ([a-z]+) with value (\d+)$"""){ (varName:String, value:Int) => vars += varName -> value } When("""^I multiply ([a-z]+) \* ([a-z]+)$"""){ (var1:String, var2:String) => result = vars(var1) * vars(var2) } Then("""^I get (\d+)$"""){ (expectedResult:Int) => assert(result === expectedResult) } } Note you can use your natural language. Simply import another trait instead of EN. Check the bitbucket repo for an example of a scenario written in [catalan](http://en.wikipedia.org/wiki/Catalan_language). 5. Launch or reload your sbt, then run `cucumber` and see the magic happen! And if you forgot to define a step, you'll get a message that will help in defining it. Something like: [info] You can implement missing steps with the snippets below: [info] Given("""^a variable x with value (\d+)$"""){ (arg0:Int) => [info] //// Express the Regexp above with the code you wish you had [info] throw new PendingException() [info] } ## Conclusions There is no excuse to not be using BDD in your Scala projects. Just try it and you'll never go back. Ah! And thanks to skipoleschris, the person behind the Cucumber SBT plugin, for being so helpful in solving a dependency problem I had. P.S. Ok... The style is not precisely functional with those BDD steps having state. Any ideas on this stuff are welcome, of course.

#You Cannot Correctly Represent Change Without Immutability A recent comment in one of our past articles made me remember this excellent article on immutability. A must read.

"Uncle" Bob Martin, in ["Why Clojure"](http://thecleancoder.blogspot.com.es/2010/08/why-clojure.html), writing about ["The Structure and Interpretation of Computer Programs"](http://mitpress.mit.edu/sicp/) (and about Functional Programming, LISP and Clojure).

Alan J. Perlis

@agile_jordi (http://bit.ly/L7V6Hx)

@agile_jordi http://twitter.com/agile_jordi

Are you lean enough? Let's validate the hypothesis: Take some days and come here. Tell me you are coming and/or join our clojure and scala meetup groups. Code, chat, laugh, whatever. And let's have a beer. Or let us show you somewhere to have a real "arròs a la paella" as a reward after a hard FP coding dojo!

This is a nice introduction to scala, akka, play and heroku. I specially liked the first part (the intro to Scala and akka) as it gives a godd overview of the principles and philosophy behind the scala language and its peculiar approach to functional programming, specially targeted to java programmers. It is also a good introduction to functional programming from a pragmatic point of view: Instead of babbling about functors, monads, calculus, etc. it talks about what kind of stuff can be done more easily in a functional style and explains why it is so.

by @func_io (http://twitter.com/#!/func_io)