ScaTDD: Casting an eye over three major Test frameworks in Scala

Testing has traditionally been the gateway process for Scala development at a number of Java shops looking to evolve their tech stack with minimal disruption or committment. This posts hopes to cover three of the main testing frameworks in the Scala landscape, (Specs2, Scalatest and Scalacheck) with an example of the classic FizzBuzz test, for how they can be used for fun and profit.

3 commands, 2 dependencies, 1 minute.. blast off with Scala development using the mvn archetype

I go to a fair few (probably too many), tech conference and meetups. A passing observation, is that if code samples are shown a proportion of the audience will try to run them while following along. Initially, this seems counter intuitive (to try and both listen and absorbing information while also trying to perform actions as a background task), though my own experience is that this works suprisingly well for practical activities, (maybe the multi-sensory exposure helps learning and retention ?).
Continue reading

Scala + JDK 6 annotations = Simple REST service in ~ 50 LOC

This is a post I’d been meaning to submit for some time and is the chaser sibling to the SOAP fuelled scrub up, showing how to create a very simple service in the Restful style using only Java 6 and the Scala language (note I personally use Scala v2.9). Continue reading

Partial updates in an immutable World

This post was prompted by a conversation with a good friend, who is an experienced Java developer taking their first, tentative, steps towards becoming a Scala programmer. Basically, the conversation went as follows:

“…Immutability seems good and like a goal I should aim for. How can I get this in my domain objects without having to provide a multiplicity of constructors to do partial updates ? Is it really that big a deal ? I’ve rarely had to worry about this stuff in Java at all !”

Both fair question, which I’ll try to address in the remainder of this post. Continue reading

A crash course in Scala types

After many years of Java development, discovering Scala’s type system and related features was something of a departure for me. Suffice to say GADT wasn’t my first four letter utterance when learning about pattern matching on types, let alone what, when and how to use variance annotations and generalized type constraints. To kick things off, here’s a ‘small but powerful‘ few lines of buzzword bingo on the type system:

…Scala is a statically, strongly, typed language, with implicit type inference and support for structural and existential types. It also features parameterized types, abstract and phantom types and is capable of implicitly converting between datatypes. These core capabilities are utilized by context and view bounds and complimented by generalized type constraints, to provide powerful compile time contracts. Furthermore, Scala supports declaration site type annotations to facilitate invariant, covariant and contravariant type variance…

In a word, Ouch !

In the remainder of this post, I’ll try to demystify these concepts and sew the seeds of intrigue for further investigation.
Continue reading

Pattern Matching in Scala distilled

As the name suggests, pattern matching enables the checking of a sequence of tokens for the presence of the same pattern. Beyond the Scala language, pattern matching is a commonly employed programming technique in a number of (predominantly functional), programming languages including Haskell, Erlang, ML, Clojure and Prolog. In this post I’ll cover the different flavours of pattern matching in Scala, as well as providing reference to typesafe null and extractor patterns to cover the idiomatic usage of pattern matching in Scala.

Power with control… control structures and abstractions in Scala

So ramping up with the Scala 101 series, I thought now is an appropriate juncture to introduce control structures in Scala. To a certain extent, working with the Scala language presents a vista wherein the developer is afforded much greater freedom than in many other environments, but therein lies a great many choices and a sense of responsibility. As such, I’ve consciously tried to restrict this post to covering some of the main flavours and options for control-flow and ¬†iteration within Scala, how they differ and provide examples of usage. Continue reading

Scala + JDK6 annotations = Simple Web Service < 20 LOC

I’ve recently had the fortune to inherit the Promethean task of evaluating a number of vendor systems, whose main interface to existing ‘enterprise‘ software/systems is via a SOAP Web Service gateway. As intriguing as this may sound, I’ve found the snippet of code below to be an incredibly useful starting point when trying to rapidly knock up a sample integration endpoint. Continue reading

Notes from… Scaling webapps with Akka [live blog]

Akka is a Scala based framework for creating robust and scalable distributed applications, and (along with the Lift web framework), has been one of the poster boys for the Scala dev community. Given the [relative] naivety of Scala programming language I was intrigued to see what was actually possible with these frameworks from the trenches. Tonight’s presentations from Maciej Matyjas (@matyjas) at skillsmatter offered to show exactly these possibilities using both Lift and Akka to build a scalable webapp with remote actors, and also using sbt as the build tool (sbt purporting to be the Scala good cop equivalent of Maven).

Continue reading