MODERN DEVELOPMENT IN SCALA Alexey Novakov, Ultra Tendency, 2020 

GOAL Alexey Novakov, Ultra Tendency, 2020 Get an idea on how typical Scala application development looks like today and what are the basic tools for that 

AGENDA Basics of SBT SBT plugins REST API with Akka-HTTP Alexey Novakov, Ultra Tendency, 2020 

Scala Build Tool (SBT) Download: https://www.scala-sbt.org/download.html Project Template execute in shell: sbt new scala/scala-seed.g8 name [Scala Seed Project]: akka-http-api Giter8 allows to create your own project template and host on GitHub: sbt new novakov-alexey/scala-service.g8 —> https://github.com/novakov-alexey/scala-service.g8 Alexey Novakov, Ultra Tendency, 2020 

SBT Tasks (commands) sbt clean - deletes previously built files sbt compile - compiles source code sbt test - run tests, if any exists sbt run - runs detected “Main” class sbt package - makes jar file … user can define new tasks in *.sbt files Alexey Novakov, Ultra Tendency, 2020 

Scala IDEs IntelliJ + Scala Plugin VSCode + Metals (Scala LSP) Alexey Novakov, Ultra Tendency, 2020 

Build Definition build.sbt Alexey Novakov, Ultra Tendency, 2020 import Dependencies._ ThisBuild / scalaVersion := "2.13.1" ThisBuild / version := "0.1.0-SNAPSHOT" ThisBuild / organization := "com.example" ThisBuild / organizationName := "example" lazy val root = (project in file(".")) .settings( name := "akka-http-api", libraryDependencies += scalaTest % Test ) Scope: build level, default for all sub-projects 

Managed Dependencies import Dependencies._ lazy val root = (project in file(".")) .settings( libraryDependencies += scalaTest % Test ) import sbt._ object Dependencies { lazy val scalaTest = "org.scalatest" %% "scalatest" % “3.0.8" } Alexey Novakov, Ultra Tendency, 2020 build.sbt project/ Dependencies.scala 

libraryDependencies += “org.scalatest" %% "scalatest" % "3.0.8" % Test groupID % artifactID % revision % configuration "org.scalatest" % “scalatest_2.13” % "3.0.8" % Test %% - matches current build Scala version Alexey Novakov, Ultra Tendency, 2020 

- SBT is using Coursier to download Ivy or Maven dependencies Coursier - Pure Scala Artifact Fetching Alexey Novakov, Ultra Tendency, 2020 

Example: REST API in Akka-HTTP libraryDependencies ++= Seq( akkaHttp, akkaStreams, … ) lazy val akkaHttp = "com.typesafe.akka" %% "akka-http" % "10.1.11" lazy val akkaStreams = “com.typesafe.akka" %% "akka-stream" % "2.6.1" Alexey Novakov, Ultra Tendency, 2020 

HTTP Server • Akka-HTTP • Options: 1. Core Server API (HttpRequest => HttpResponse) 2. Routing DSL (Directives) • helps to make code DRY • but requires to learn a DSL (error-prone, time consuming) 

Run in shell: sbt new novakov-alexey/scalaboot.g8 Giter8 Template Includes: Akka-HTTP, Circe and bunch of useful SBT plugins 

HTTP Endpoints Get Order by id: GET /api/v1/exchange/ Create new Order: POST /api/v1/exchange (JSON body) final case class Quote(bid: BigDecimal, ask: BigDecimal, ticker: String) final case class Order(id: Long, quotes: List[Quote]) Alexey Novakov, Ultra Tendency, 2020 

SBT Plugins 

sbt-revolver - restarts running application automatically, if source files are modified addSbtPlugin("io.spray" % "sbt-revolver" % "0.9.1") sbt “~reStart” - enables a super-fast development turnaround for your Scala applications 

sbt-tpolecat addSbtPlugin( “io.github.davidgregory084" % "sbt-tpolecat" % “0.1.10" ) - enables scalac options according to Rob Noris recommendations. - P.S. the same options can be enabled manually 

• Implement HTTP routes • Start HTTP Server • Test API via client …. let’s dive into the code TODO 

sbt-native-packager SBT native packager lets you build application packages in native formats: •Universal zip,tar.gz, xz archives •deb and rpm packages •dmg •msi •docker images •graalvm native images # universal zip sbt universal:packageBin # docker image sbt docker:publishLocal 

sbt-release addSbtPlugin( "com.github.gseitz" % "sbt-release" % “1.0.12" ) - provides customisable release process - steps to configure: - increment scala project version - run tests - check git branch has no uncommitted changes - push new git tag - create new snapshot version 

Thanks. Q & A https://github.com/novakov-alexey Twitter: @alexey_novakov 

IMAGES 1. Drone: https://unsplash.com/photos/0RzFRYMEosc 2. Puzzle: https://unsplash.com/photos/sOK9NjLArCw 3. Basket: https://unsplash.com/photos/j6brni7fpvs