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)

Chapter 15

  1. How do you map the endpoint with the query parameter to a REST call?
def answer(parameter: Int): ServiceCall[NotUsed, Done]

override def
descriptor: Descriptor = {
import Service._
restCall(Method.POST, "/answer?parameter", answer _)
  1. What is the recommended serialization format for persistent entities?

Lagom's recommended serialization format is JSON.

  1. Can you explain why clustering is required in order to use persistence in Lagom?

Lagom's persistence is implemented on top of Akka persistence. Akka requires each persistent actor to have a unique persistence ID. In a microservice landscape, each service is supposed to have multiple instances at the same time. Without clustering, there will be multiple persistent actors with the same ID storing events into the same database, which will corrupt data...