Skip to main content

Second try with Scala and REST

As I mentioned in my previous post I tried to create a simple REST service with Scala and spray.io, but that turned out to be unbelievably difficult. A second try with Scala and REST turned out to be successful.

Play to the rescue


When my experiment with spray.io didn't work out I had an idea to try out Play 2 as a base to my REST service. Working with Play 2 was a walk in the park compared to spray.io even though not entirely painless but much easier and less frustrating.

Starting out with Play 2 was really quick thanks to a good documentation and examples that are up to date. Basically I just ran the command play new appName and started coding.

So far I have REST service and a in-memory implementation of todo tasks with some unit tests. REST service is all Play 2 with routes and a single application class. The current service layer implementation is a single class with tasks in a mutable Map where a individual task is a case class, so just some basic Scala code.

I really like Play 2 so far but I'm a bit concerned of how much dependencies Play 2 brings with it as default. Currently I have 92 jars in referenced libraries of my project, all from default initialization of play application. Sure some of these are test library dependencies but still that's a lot of libraries.

Unit testing Scala code


Play 2 automatically includes as a dependency the specs2 library that's a unit and acceptance testing library for Scala. I had never used specs2 and the bdd style definition of tests was a bit odd to me but I decided to give it a try.

After a few initial wtf's I got the hang of it pretty quickly and was able create some basic unit tests for my service implementation. I've only scratched the surface with specs2 but it seems to do the job and has quick learning curve and so far the provided documentation has been enough to get me going.

What's next


Next step in my adventures in the world of Scala will be to try use some real data storage to persist the todo applications data. I think I'll try out with MongoDB and after that some other very different alternatives like Redis and MariaDB. 


Code shared publicly


As I use code and examples provided by others I too am sharing my code and putting it publicly reviewed by others. It's all shared through my github account at https://github.com/jorilytter/simple-todo, feel free take a look.

Comments

Popular posts from this blog

Simple code: Immutability

Immutability is a special thing that in my mind deserves a short explanation and praise. If you're familiar with functional programming you surely recognice the concept of immutability because it's a key ingredient of the paradigm. In the world of object oriented programming it's not as used and as easy to use approach but there are ways to incorporate immutability to parts of the code and I strongly suggest you to do so. Quick intro to immutablity The basic idea of immutability is unchangeable data.  Lets take a example. We have a need to modify a object's property but because the object is immutable we can't just change value but instead we make a copy of the object and while making the copy we provide the new value for the copy. In code it looks something like this. val pencil = Product(name = "Pencil", category = "Office supply") val blackMarker = pencil.copy(name = "Black marker") The same idea can be applied in functions and metho

Simple code: Contracts

Code works around contracts and contracts should be carefully thought and crafted. What are contracts A High abstraction level of contracts for code are API's. They define a interface that is basically a contract that the producer and consumer of the API agree to use to communicate with each other. Two common forms of API's are libraries that are used in code and external API's  that are used via HTTP, RPC etc. When thinking in a bit deeper contracts consist firstly of functions, methods or external endpoints and secondly of data, more precisely on data models and data types within the models.   Defining contracts Contracts should always be defined with careful thought. I've come accross few times to someone saying that "this is for intenal use only so it doesn't need to defined and/or documented as thoughtfully as a public API would be" but I disagree with that. The same care should be be given to internal and external contracts because the contracts are

Simple code: Functions and methods

What makes a good function or method? I don't think it's a single thing but a combination of things where each is significant. If one the things is flawed it affects to all others and the whole function is flawed. So what are those "things"? Have a meaningful name Function should have a name that describes it's purpose or functionality. When a function has a meaningful name it's easy to read and understand what's it's purpose. Let's take a example. If function's purpose is to find a customer by it's id a good name could be findCustomerById(id: String) or it could just as well be just  findCustomer(id: String) because the function signature implies that the customer is found by it's id the word find also implies that the customer might be found or it might not be found. If the function's name would be changed to getCustomer(id: String) it's meaning changes because now it implies that there's no fallback, the customer is e