Book Image

Building Applications with Scala

By : Diego Pacheco
Book Image

Building Applications with Scala

By: Diego Pacheco

Overview of this book

<p>Scala is known for incorporating both object-oriented and functional programming into a concise and extremely powerful package. However, creating an app in Scala can get a little tricky because of the complexity the language has. This book will help you dive straight into app development by creating a real, reactive, and functional application. We will provide you with practical examples and instructions using a hands-on approach that will give you a firm grounding in reactive functional principles.</p> <p>The book will take you through all the fundamentals of app development within Scala as you build an application piece by piece. We’ve made sure to incorporate everything you need from setting up to building reports and scaling architecture. This book also covers the most useful tools available in the Scala ecosystem, such as Slick, Play, and Akka, and a whole lot more. It will help you unlock the secrets of building your own up-to-date Scala application while maximizing performance and scalability.</p>

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Building Applications with Scala
Diego Pacheco
Dec, 2016 | 344 pages
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Table of Contents (17 chapters)
Building Applications with Scala
Building Applications with Scala
Credits
Credits
About the Author
About the Author
Acknowledgments
Acknowledgments
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Introduction to FP, Reactive, and Scala
Introduction to FP, Reactive, and Scala
Functional programming
Principles of functional programming
Installing Java 8 and Scala 2.11
Read Eval Print and Loop - REPL
Scala Hello World using the REPL
Scala language - the basics
Scala variables - var and val
Creating immutable variables
Scala conditional and loops statements
For comprehensions
Scala collections
Monads
Scala class, traits, and OO programming
Traits and inheritance
Case classes
Pattern Matcher
Partial functions
Package objects
Functions
Partial application
Curried functions
Operator overloading
Implicits
Futures
Reactive Programing and RxScala
Summary
2
Creating Your App Architecture and Bootstrapping with SBT
Creating Your App Architecture and Bootstrapping with SBT
Introducing SBT
Installing SBT on Ubuntu Linux
Getting started with SBT
Adding dependencies
Generating Eclipse project files from SBT
Application distribution
Hello world SBT / Scala App
Bootstrapping our Play framework app with Activator
Activator shell
Activator - compiling, testing, and running
Summary
3
Developing the UI with Play Framework
Developing the UI with Play Framework
Getting started
Creating our models
Creating routes
Creating our controllers
Working with services
Configuring the Guice module
Working with views(UI)
Summary
4
Developing Reactive Backing Services
Developing Reactive Backing Services
Getting started with reactive programming
Play framework and high CPU usage
Summary
5
Testing Your Application
Testing Your Application
Unit testing principles
Testing with Junit
Behavior-Driven Development - BDD
MyFirstPlaySpec.scala - First BDD with ScalaTest and the Play framework
Testing with Play framework support
Testing routes
Controller testing
Summary
6
Persistence with Slick
Persistence with Slick
Introducing the Slick framework
MySQL setup
Configuring Slick in our Play framework app
FPM Mapping
Slick evolutions
Refactoring services
Refactoring controllers
Configuring DAO packages in Guice
Refactoring tests
Generic mocks
Service tests
Controller tests
Running the application
Summary
7
Creating Reports
Creating Reports
Introducing JasperReports
JasperReports workflow
Jasper sessions
Installing Jaspersoft Studio 6
Configuring MySQL Data Adapter in Jaspersoft Studio
Creating a product report
Creating a review report
Creating an image report
Integrating JasperReports with Play framework
Routes - adding new report routes
New centralized reports UI
Summary
8
Developing a Chat with Akka
Developing a Chat with Akka
Adding the new UI introduction to Akka
Introduction to the Actor model
Message exchange and mailboxes
Coding actors with Akka
Actor routing
Persistence
Creating our chat application
The chat protocol
The chat controller
Configuring the routes
Working on the UI
Adding Akka tests
Summary
9
Design Your REST API
Design Your REST API
Introduction to REST
REST API design
Creating our API with REST and JSON
Creating a Scala client
Creating our REST client proxies
Summary
10
Scaling up
Scaling up
Standalone deploy
Reports folder
Changing report builder
Defining the secret
Running the standalone deploy
Architecture principles
Scalability principles
Mid-Tier load balancer, timeouts, Back pressure, and caching
Scaling up microservices with an Akka cluster
Scaling up the infrastructure with Docker and AWS cloud
Summary

Play framework and high CPU usage

If you notice your CPU usage going higher than it should, do not worry; there is a fix for it. Actually, the issue is related to SBT. Just make sure that, when you run Activator, you pass the following parameter:

$ activator -Dsbt.task.forcegc=false.

Going back to ReactiveWebStore, let's create new routes. Open ReactiveWebStore/conf/routes:

    GET   /rnd/double  
    controllers.RndDoubleGeneratorController.rndDouble 
    GET   /rnd/call    controllers.RndDoubleGeneratorController.rndCall 
    GET   /rnd/rx      controllers.RndDoubleGeneratorController.rxCall 
    GET   /rnd/rxbat      
    controllers.RndDoubleGeneratorController.rxScalaCallBatch

Once we have the new routes, we need to create the new controller. This controller needs to be located with the other controllers at ReactiveWebStore/app/controllers.

RndDoubleGeneratorController

The RndDoubleGeneratorController class file should look like this:

    @Singleton 
...
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