Scala Club: Modern Development in Scala

Basics of SBT

SBT plugins

REST API with Akka-HTTP

Transcript

1. MODERN
   DEVELOPMENT
   IN
   SCALA
   Alexey Novakov, Ultra Tendency, 2020
   

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2. 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
   

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

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4. 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
   

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5. 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
   

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

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7. 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
   

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8. 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
   

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9. 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
   

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

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11. 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
    

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12. 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)
    

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

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14. 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
    

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15. SBT Plugins
    

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16. 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
    

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17. 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
    

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

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19. 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
    

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20. 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
    

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

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

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