Your first Web application with Play and Scala

Today we are going to develop a simple play application using Scala.

To do so we must have sbt installed to our system.

Once installed we issue the command

sbt new playframework/play-scala-seed.g8

Then we are presented with an interactive terminal in order to pass valuable information.

name [play-scala-seed]: PlayStarter
organization [com.example]: com.gkatzioura
scala_version [2.11.8]: 
scalatestplusplay_version [2.0.0]: 
play_version [2.5.13]: 

Then let us check what we have just created

cd playstarter
sbt run

Navigate to http://localhost:9000 and you have a basic Play hello world.

By looking to our project structure, as expected, we have a directory with our controllers.
Consider our request being handled as an action. We issue a request and we receive an html view.

  def index = Action { implicit request =>
    Ok(views.html.index())
  }

As you can see we the html that is rendered is located at the views directory. Play comes with Twirl as a template engine.

At conf/routes we can see how the route is configured to the index action

Let’s add a simple action to that controller that returns a text body.

  def greet(name: String) = Action {
    Ok("Hello " + name)
  }

We have to edit the routes file to specify the new route and the get parameter

GET     /greet                      controllers.HomeController.greet(name)

Then issue a request at http://localhost:9000/greet?john

On the next step we shall add a new route with a path param

Suppose we want to retrieve the total logins for a user.
We implement an action that send a fake number

  def loginCount(userId: String) = Action {
    Ok(14)
  }

And then we register the route

GET     /user/:userId/login/count          controllers.HomeController.loginCount(userId)

By issuing the request http://localhost:9000/user/18/login/count
we shall receive the number 14.

To sum up we just implemented our first Play application. We also implemented some basic actions to our controller and achieved to pass some path and request parameters.

A journey with Scala

To those who are regular visitors of this blog, it is well known that when it comes to developing code I am a Spring/Java guy. Also I use different technologies like node or python but this depends¬†largely on the project’s needs.

Due to some recent projects and courses involving Spark, stumbling on Scala was inevitable. After some investigation I decided to adopt it, as one of my main tools and there are many reasons for that.

From a Java Developers perspective

  • It evolves faster
  • It has Flexible syntax
  • It is static typed
  • It is pretty recent thus exciting, but in a JVM flavor

I remember back then when I was anticipating the release of Java 7. Lambdas, streams and put some functional programming into action. All those features that Scala provided. Unfortunately lambdas were dropped from Java 7, and released as part of Java 8. Thus it took 3 years to get your hands on lambdas ūüė¶

The Scala syntax is great and increases productivity. I really fancy the fact that you can skip a lot of boilerplate that your had to deal with java. Let alone the options like tuples, switches and parameter name specification on function calls. The list could go on and on.

I used both dynamic and static typed languages however by developing mainly on Java I am a bit biased. I believe that static typing is a good choice because you can detect errors early, build reliable code and increase maintainability. Also it makes collaboration with others much easier.

Every new technology is exciting and feels like a new toy. However adopting a new technology comes with the lack of libraries and frameworks (node anyone?) that were essential for your development process. Fortunately you can always bet on the JVM and use your Java libraries with your Scala source code.

From a ecosystem perspective

If you come from Java EE or Spring MVC, you have an already prooved and tested framework for your web application.  Luckily Play comes to the rescue. Is Play sufficient for all your needs? I doubt. But frameworks evolve and since we live in a  microservices-architecture era having some Java components does the work.

From  a project perspective.

The cloud and the overall technological burst has brought a variety of different types of applications. Developing applications has become more challenging and some of them involve big data processing, streaming and machine learning. Scala is first place on this type of applications, thus if your objective is to work on the big data world mastering Scala will definitely assist you.

It does the filtering for you. As mentioned previously Spring/Java can be used for various type of projects, batch Applications, CMS apps, Rest apis etc. Scala has a more specific identity and targets certain type of projects. By searching for opportunities and contracts that include¬†Scala, you already have a sense of the project’s nature and the challenges ahead.

At last

Talk is cheap! There are many tutorials ahead to author and document my experience. Stay tuned for more Scala content.