[ScaVa->Scala] Introduction to Scala Development

前言

這件文件是在公司內部向一些新踏入Scala領域的同事們介紹所使用的資料，因此適合有程式開發經驗，並且想Scala領域中的朋友們。
底下列了一些學習Scala的資源、並列出一些我們自己開發常用到的Libraries並適合新手來學習使用的。
最底下有兩各sample projects，以縮網址為題目來分別實作一個library與提供REST服務的web application。

Scala Introduction

Learning Scala

• Scala for Java Programmer

• Scala for the Intrigued

• The Neophyte’s Guide to Scala

• Scala Excercises - The easy way to learn Scala.

• Intro to ScalaTest

Functional Programming

Category theory jargon cheat sheet

• Functor supports map.
• Applicative functor extends functor and adds pure and <*>.
• Monad extends applicative and adds flatMap (a.k.a bind).
• Semigroup supports append.
• Monoid extends Semigroup and adds zero.

Scala Libraries, Frameworks and Software.

Check most popular scala libraries at GitHub - awesome-scala.

Common use libraries in our development.

• Distributed System

  • Akka — A toolkit and runtime for building highly concurrent, distributed, and fault tolerant event-driven applications.

• Database

  • Elastic4s — A scala DSL / reactive client for Elasticsearch
  • ReactiveMongo — Reactive Scala Driver for MongoDB.
  • rediscala — Non-blocking, Reactive Redis driver for Scala (with Sentinel support)

• Web Framework

  • Play — Makes it easy to build scalable, fast and real-time web applications with Java & Scala.
  • Scalatra — Tiny Scala high-performance, async web framework, inspired by Sinatra.
  • Spray — A suite of scala libraries for building and consuming RESTful web services on top of Akka.
  • Finatra — A sinatra-inspired web framework for scala, running on top of Finagle.
  • Socko — An embedded Scala web server powered by Netty networking and Akka processing.

• HTTP client

  • Dispatch — Library for asynchronous HTTP interaction. It provides a Scala vocabulary for Java’s async-http-client.
  • Spray — Actor-based library for http interaction.

• Json

  • json4s — Project aims to provide a single AST to be used by other scala json libraries.
  • jackson-module-scala — Add-on module for Jackson to support Scala-specific datatypes.

• Config

  • config — Configuration library for JVM languages http://typesafe.com. (Akka embedded this config module.)

• Logger

  • Grizzled-SLF4J — A simple, Scala-friendly front-end to SLF4J.

• Testing

  • ScalaTest — A testing tool for Scala and Java developers.
  • Gatling – Async Scala-Akka-Netty based Stress Tool.

• Extensions

  • Scalaz — An extension to the core Scala library for functional programming.
  • Scala Async — An asynchronous programming facility for Scala.
  • Scalactic — Small library of utilities related to quality that helps keeping code clear and correct. (ScalaTest embedded this lib.)

Development Environment

Scala

SBT (Simple Build Tool)

http://www.scala-sbt.org/

Package Plugins http://www.scala-sbt.org/release/docs/Community-Plugins.html

• sbt-native-packager: https://github.com/sbt/sbt-native-packager
• sbt-assembly: https://github.com/sbt/sbt-assembly
• sbt-onejar (Packages your project using One-JAR™): https://github.com/sbt/sbt-onejar

IDE - Intellij Idea

You’re welcome to use any text editor or IDE what you like. e.g. vim, TextMate, Sublime, Notepad++, cloud9…

However my favorite IDE for Scala development is Intellij Idea, which is most powerful IDE for scala development.

Directory Structure

Ref: SBT Directory Structure

source code

src/
  main/
    resources/
       <files to include in main jar here>
    scala/
       <main Scala sources>
    java/
       <main Java sources>
  test/
    resources
       <files to include in test jar here>
    scala/
       <test Scala sources>
    java/
       <test Java sources>

sbt build definition files

build.sbt
project/
  Build.scala

Others

• Markdown
• Git
• Chef

Demo

• URL Shortener
  URL Shortener

• URL Shortener - Socko-Web implementation
  Shortener-Sockoweb