Book Image

Learn Scala Programming

By : Slava Schmidt
Book Image

Learn Scala Programming

By: Slava Schmidt

Overview of this book

The second version of Scala has undergone multiple changes to support features and library implementations. Scala 2.13, with its main focus on modularizing the standard library and simplifying collections, brings with it a host of updates. Learn Scala Programming addresses both technical and architectural changes to the redesigned standard library and collections, along with covering in-depth type systems and first-level support for functions. You will discover how to leverage implicits as a primary mechanism for building type classes and look at different ways to test Scala code. You will also learn about abstract building blocks used in functional programming, giving you sufficient understanding to pick and use any existing functional programming library out there. In the concluding chapters, you will explore reactive programming by covering the Akka framework and reactive streams. By the end of this book, you will have built microservices and learned to implement them with the Scala and Lagom framework.
Table of Contents (19 chapters)

Lagom's APIs

As before, we will start with an implementation of the simplest of our workers, which just performs basic mathematical operations in order to do its work with Cook, which makes RawCookies out of Dough.

Service API

In order to define our Cook as a service we need to implement a special interface called a service descriptor. The service descriptor defines two aspects of a Lagom service:

  • The service signature: How the service should be called and its return type
  • The service meta data: How the service call is mapped to the transport layer, for example to the REST call

The service descriptor extends Lagom's Service trait and in its simplest form just needs to override the descriptor method. This is what...