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Java-Scala interoperability Sean Sullivan April 19, 2016 Portland Java User Group

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• software engineer • 20 years Java • 5 years at Gilt • back office systems @ Gilt About me

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• Scala @ Gilt.com • Scala on the Java VM • code examples Agenda

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www.gilt.com

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https://www.gilt.com/checkout

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“The Scala 2.11.x series targets Java 6" http://www.scala-lang.org/news/2.11.0/

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http://scala-lang.org/news/2.12-roadmap/ “The official Scala 2.12 distribution will be built for Java 8 (and thus require it)”

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Scala case classes and JSP’s

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case class Thing( name: String, color: String)

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thing.jsp <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

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JSP expression language expects a JavaBean with “getter” methods

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import scala.reflect.BeanProperty case class Thing( @BeanProperty name: String, @BeanProperty color: String) @BeanProperty annotation

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Collections

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• convert java.util.List to Scala collection • convert java.util.Set to Scala collection • convert java.util.Map to Scala collection • convert Scala List to java.util.List Common scenarios

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import scala.collection.JavaConverters._

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import java.util.{ArrayList => JArrayList}
 import scala.collection.JavaConverters._
 
 val jArrayList = new JArrayList[String]
 jArrayList.add("a")
 jArrayList.add("b")
 jArrayList.add("c")
 
 val scalaList = jArrayList.asScala
 
 scalaList should be (List("a", "b", "c"))


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Google Guava library

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• com.google.common.base.Optional • com.google.common.util.concurrent.ListenableFuture

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Guava @ Gilt

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Guava Optional -> Scala Option Scala Option -> Guava Optional

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import com.gilt.gfc.guava.GuavaConverters._

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Guava Future -> Scala Future Scala Future -> Guava Future

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import com.gilt.gfc.guava.future.FutureConverters._

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Java 8

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https://github.com/scala/scala-java8-compat

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import scala.compat.java8.FutureConverters._ Java 8 Future to Scala Future

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import scala.compat.java8.OptionConverters._ java.util.Optional to scala.Option

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https://github.com/sullis/java-scala-interop-examples

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The end

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