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Slick - The Structured Way
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Slick (part of the Typesafe stack) is a modern database query and access library for Scala, based on functional principles. It allows you to write queries as if you are working with regular Scala collections. In this presentation we’ll have a deep dive into how you can use this library in real projects. How to map your tables and queries to structured objects, how to create more advanced queries with multiple joins, how to setup integration tests against an in-memory database and how you can integrate Slick with the Play Framework are all questions which will have been answered at the end of this presentation. Originally presented on the BeScala user group.
Yennick TrevelsFollow
Reactive Application ConsultantAdvertisement
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Slick - The Structured Way
- Slick The Structured Way
- YENNICK? YANNICK? JANNICK? Reactive Applications Consultant Certified Typesafe “Fast Track to Scala” trainer @SlevinBE yennicktrevels.com Yennick.Trevels@xploregroup.be
- WHY SLICK? Option(Anorm).orElse(Hibernate).orElse(Slick) Pure Scala Immutable data structures DB agnostic code Type safety
- TALK MOTIVATION
- MEAT OF THE TALK
- ESSENTIALS Build queries with Scala Lifted embedding Query result result rows ID TITLE ID FIRSTNAME LASTNAME 1 “Scala” 10 Yennick Trevels 1 “Scala” 11 Eric Loots 2 “Slick” 12 Filip Maelbrancke
- IMPORTS Database specific Database agnostic import use Play-Slick plugin
- SESSION SCOPE
- TRANSACTION SCOPE
- SAMPLE DATABASE MEETING DOCUMENT ATTENDEE_LINK ATTENDEE ID … MEETING_I D ATTENDEE_I D ID … MEETING_ID ID … ID …
- LEVEL 1: MAPPING TABLES
- TABLE MAPPING: MEETING
- TABLE MAPPING: MEETING
- TABLE MAPPING: LINK TABLE
- LEVEL 2: BASIC QUERIES
- FILTER STATEMENTS Slick SQL === instead of ==
- FILTER STATEMENTS Slick Brackets Put || or && at end of line ↵
- SORTING Slick SQL
- EXISTS Slick SQL
- DEFINING THE RESULT Slick SQL Result
- DEFINING THE RESULT Slick SQL Result
- DEFINING THE RESULT Slick meetings.list List[Meeting] meetings.first Meeting or NoSuchElementException meetings.firstOption Option[Meeting]
- LEVEL 3: ADVANCED QUERIES
- INNER JOIN Slick SQL Result
- INNER JOIN (RESULT MAPPING) Slick Result
- OUTER JOINS (THE PROBLEM) Slick
- OUTER JOINS (THE PROBLEM) ID TITLE ID MEETING_ID ATTENDEE_ID 1 “Scala” NULL NULL NULL 2 “Slick” 10 2 20 3 “Slick” 11 2 21 ID TITLE 1 “Scala” 2 “Slick” ID MEETING_ID ATTENDEE_ID 10 2 20 11 2 21 Left Join Ref: http://www.slideshare.net/skillsmatter/patterns-for-slick-database-applications
- OUTER JOINS Slick Result
- OUTER JOINS (RESULT TRANSF.) Slick
- THE ? FUNCTION Solution expected somewhere this year
- LEVEL 4: INSERT/UPDATE/DELETE
- INSERT Slick SQL
- UPDATE Slick SQL
- DELETE Slick SQL
- LEVEL 5: SLICK + PLAY
- APPLICATION.CONF
- DATABASE AGNOSTIC IMPORTS
- DB WRAPPER
- LEVEL 6: INTEGRATION TESTING
- TABLE CREATION Using Play-Slick plugin classes
- IN-MEMORY DATABASE CONFIG
- TEST DATA SETUP Just use Slick…
- CONCLUSION
- THOUGHTS ON SLICK + Lightweight + Level of control + Production ready - Documentation - Generated Queries (readability)
- Development Coaching Training Hello Scala seminarJune 25th 2014 Fast Track to Scala October 09th 2014 Fast Track to Akka with Scala November 04th 2014 Yennick.Trevels@xploregroup.be CONTACT US
Editor's Notes
- Build queries as if you would use Scala collections. More lightweight than Hibernate
- Slick doesn’t use standard Scala types, but lifts them into a Rep type constructor
- Import scala.slick.driver.H2Driver.simple._
- Database.forURL( "jdbc:postgresql://localhost:5432/meetings", driver = "org.postgresql.Driver" ) withSession { implicit session => //queries }
- Database.forURL( "jdbc:postgresql://localhost:5432/meetings", driver = "org.postgresql.Driver" ) withTransaction { implicit session => //queries
- This will create all the tabels based on your mapped models. For this it uses the Play-Slick plugin classes which can generate an evolution script for us, from which we can then extract the create statements. import play.api.db.slick.plugin.SlickDDLPlugin import play.api.db import scala.slick.jdbc.StaticQuery def initializeDatabase() = { implicit val app = play.api.Play.current val slickDDLPlugin = new SlickDDLPlugin(app) slickDDLPlugin .evolutionScript("default", Set("models.*"))(app).map { evolutionScript => val upEvolutions = evolutionScript.split("# --- !Downs")(0).split("# --- !Ups")(1) db.slick.DB.withSession { implicit session => StaticQuery.updateNA(upEvolutions).execute() } } }
- val inMemoryDatabase: Map[String, String] = Map( "db.default.driver" -> "org.h2.Driver", "db.default.url" -> "jdbc:h2:mem:play-test", "evolutionplugin" -> "disabled” ) "getAllMeetings" should { "return ALL meetings ordered by start date” { running(FakeApplication(additionalConfiguration = inMemoryDatabase)) { initializeDatabase() … } } }
- def insertDataset_getAllMeetings_dataset1(): Meeting = { implicit val app = play.api.Play.current db.slick.DB.withSession { implicit session => val meeting = Meeting(Some(1L), …) meetings.insertAll(meeting) meeting } }
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