Solid and Sustainable Development in Scala

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%FQFOEFODJFT // build.sbt or project/Build.scala! ! scalaVersion := “2.11.2” // or “2.10.4”! ! libraryDependencies ++= Seq(! “org.scalikejdbc” %% “scalikejdbc” % “2.1.1”,! “com.h2database” % “h2” % “1.4.181”,! “ch.qos.logback” % “logback-classic” % “1.1.2”! )

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#BTJD6TBHF import scalikejdbc._! ! ConnectionPool.singleton(! “jdbc:h2:mem:matsuri”, ! “user”, “secret”)! ! DB autoCommit { implicit session =>! sql”create table attendee (name varchar(32))”.execute.apply()! val name = “seratch”! sql”insert into attendee (name) values ($name)”.update.apply()! }! ! val names: Seq[String] = DB readOnly { implicit s =>! sql”select name from attendee”! .map(_.string(“name”)).list.apply()! } SQL statement! (PreparedStatement) execute/update! (JDBC operation) Side effect ! with DB connection Extractor

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2VFSZ%4- import scalikejdbc._! case class Attendee(name: String)! object Attendee extends SQLSyntaxSupport[Attendee] {! def apply(rs: WrappedResultSet, a: ResultName[Attendee]) = ! new Attendee(rs.get(a.name))  }! ! implicit val session = AutoSession! ! ! val a = Attendee.syntax(“a”)! val seratch: Option[Attendee] = withSQL {! select.from(Attendee as a).where.eq(a.name, “seratch”)! }.map(rs => new Attendee(rs, a)).single.apply()! ! // select a.name as n_on_a from attendee a where a.name = ? QueryDSL! (Mostly SQL) Actual SQL Query

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#PPUJONJOVUFT ! // install skinny command! brew tap skinny-framework/alt! brew install skinny! ! // create app and start! skinny new myapp! cd myapp! skinny run! ! // access localhost:8080 from your browser!

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.PEFM %"0 import skinny.orm._! import scalikejdbc._! ! case class User(id: Long, name: Option[String])! ! // companion: data mapper! object User extends SkinnyCRUDMapper[User] {! def defaultAlias = createAlias(“u”)! def extract(rs: WrappedResultSet, u: ResultName[User])! = autoConstruct(rs, u)  }! ! User.findById(123)! User.count()! User.createWithAttributes(‘name -> “Alice”)! User.updateById(123).withAttributes(‘name -> “Bob”)! User.deleteBy(sqls.eq(u.name, “Bob”)) CRUD Mapper Object! (No need to be companion) Entity Smooth APIs

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$POUSPMMFS3PVUF package controller! class UsersController extends ApplicationController {! def showUsers = {! set(“users”, User.findAll())! render(“/users/index”)  }  }! ! // Routings! object Controllers {! val users = new UsersController with Routes {! get(“/users/”)(showUsers).as(‘showUsers)  }! def mount(ctx: ServletContext): Unit = {! users.mount(ctx)! }  } Set value in request scope! (Visible in views) Expects “src/main/webapp/! WEB-INF/views/users/index.html.ssp”

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7JFX5FNQMBUF // src/main/webapp/WEB-INF/views/users/index.html.ssp! ! <%@val users: Seq[User] %>! ! ! #for (user <- users)! ! ! ! ! #end! ${user.id}${user.name} import from request scope Loop, if/else syntax! in Scalate

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*NNVUBCMF&OUJUZ // entity with behaviors! case class User(id: Long, name: Option[String])! extends SkinnyRecord[User] {! override def skinnyCRUDMapper = User  }! // data mapper! object User extends SkinnyCRUDMapper[User] {! override def defaultAlias = createAlias(“u”)! override def extract(rs: WrappedResultSet, u: ResultName[User])! = autoConstruct(rs, u)  }! ! val noNames: Seq[User] = User.where(‘name -> “”).apply()! val anons: Seq[User] = noNames.map { user => ! user.copy(name = “Anonymous”).save()! } Both of “noNames” and “anons” are immutable

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8FC$POUSPMMFS package controller! class MainController extends ApplicationController ! with concern.TimeLogging {! def index = logElapsedTime { render(“/main/index”) }! }! ! // for controllers! package controller.concern! trait TimeLogging { self: SkinnyController with Logging =>! def millis: Long = System.currentTimeMillis ! def logElapsedTime[A](action: => A): A = {! val before = millis! val result = action! logger.debug(“Elapsed time: ${millis - before} millis”)! result  }! } The “concern” just follows Rails style. Anyway, naming should be simple and! easy-to-understand for anyone

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42-0QT"T*T // A programmer belongs to a company and has several skills! ! implicit val session = AutoSession! ! val p: Option[Programmer] = withSQL {! select.from(Programmer as p)! .leftJoin(Company as c).on(p.companyId, c.id)! .leftJoin(ProgrammerSkill as ps).on(ps.programmerId, p.id)! .leftJoin(Skill as s).on(ps.skillId, s.id)! .where.eq(p.id, 123).and.isNull(p.deletedAt)! }! .one(rs => Programmer(rs, p, c))! .toMany(rs => Skill.opt(rs, s))! .map { (programmer, skills) => programmer.copy(skills = skills) }! .single! .apply() I believe everybody can understand this code Extracts one-to-many relationships here

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%FQFOEFODJFT // build.sbt or project/Build.scala! ! scalaVersion := “2.11.2” // or “2.10.4”! ! libraryDependencies ++= Seq(! //“org.scalikejdbc” %% “scalikejdbc” % “2.1.1”,! “org.skinny-framework” %% “skinny-orm” % “1.3.1”,! “com.h2database” % “h2” % “1.4.181”,! “ch.qos.logback” % “logback-classic” % “1.1.2”! )

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.BQQFST // entities! case class Company(id: Long, name: String)! case class Employee(id: Long, name: String,! companyId: Long, company: Option[Company])! ! // mappers! object Company extends SkinnyCRUDMapper[Company] {! def extract(rs: WrappedResultSet, rn: ResultName[Company]) =! autoConstruct(rs, rn)  }! object Employee extends SkinnyCRUDMapper[Employee] {! def extract(rs: WrappedResultSet, rn: ResultName[Employee]) =! autoConstruct(rs, rn, “company”)! // simple association definition! lazy val companyRef = belongsTo[Company](! Company, (e, c) => e.copy(company = c))  }

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3FBTPOBCMF ! ! val companyId = Company.createWithAttributes(‘name -> “Sun”)! val empId = Employee.createWithAttributes(! ‘name -> “Alice”, ‘companyId -> companyId)! ! val emp: Option[Employee] = Employee.findById(empId)! val empWithCompany: Option[Employee] = ! Employee.joins(companyRef).findById(123)! ! Company.updateById(companyId).withAttributes(‘name -> “Oracle”)! ! val e = Employee.defaultAlias! Employee.deleteBy(sqls.eq(e.id, empId))! Company.deleteById(companyId) Using ScalikeJBDC API! is also possible Right, these CRUD operations are not SQL-ish. However, I believe they’re reasonable because these patterns are already common enough.

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5BTLT // sbt settings! // mainClass := Some("TaskRunner")! ! // task/src/main/scala/TaskRunner.scala! object TaskRunner extends skinny.task.TaskLauncher {! register("assets:precompile", (params) => {! val buildDir = params.headOption.getOrElse(“build")! // AssetsPrecompileTask is a Scala object! skinny.task.AssetsPrecompileTask.main(Array(buildDir))! })! }! ! // skinny task:run assets:precompile [dir] Pure Scala function! task name mainClass as the dispatcher

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