Spring-boot and Scala
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Join For FreeIn this blog entry, I will slowly transform a Java based Spring-boot application completely to Scala - the Java based sample is available at this github location - https://github.com/bijukunjummen/spring-boot-mvc-test
To start with, I had the option of going with either a maven based build or gradle based build - I opted to go with a gradle based build as gradle has a greatscala plugin, so for scala support the only changes to a build.gradle build script is the following:
... apply plugin: 'scala' ... jar { baseName = 'spring-boot-scala-web' version = '0.1.0' } dependencies { ... compile 'org.scala-lang:scala-library:2.10.2' ... }Essentially adding in the scala plugin and specifying the version of the scala-library.
Now, I have one entity, a Hotel class, it transforms to the following with Scala:
package mvctest.domain .... @Entity class Hotel { @Id @GeneratedValue @BeanProperty var id: Long = _ @BeanProperty var name: String = _ @BeanProperty var address: String = _ @BeanProperty var zip: String = _ }
With the entity in place a Spring-data repository for CRUD operations on this entity transforms from:
import mvctest.domain.Hotel; import org.springframework.data.repository.CrudRepository; public interface HotelRepository extends CrudRepository<Hotel, Long> { }
to the following in Scala:
import org.springframework.data.repository.CrudRepository import mvctest.domain.Hotel import java.lang.Long trait HotelRepository extends CrudRepository[Hotel, Long]And the Scala based controller which uses this repository to list the Hotels -
import org.springframework.web.bind.annotation.RequestMapping import org.springframework.stereotype.Controller import mvctest.service.HotelRepository import org.springframework.beans.factory.annotation.Autowired import org.springframework.ui.Model @Controller @RequestMapping(Array("/hotels")) class HotelController @Autowired() (private val hotelRepository: HotelRepository) { @RequestMapping(Array("/list")) def list(model: Model) = { val hotels = hotelRepository.findAll() model.addAttribute("hotels", hotels) "hotels/list" } }
Finally, Spring-boot based application requires a main class to bootstrap the entire application, where this bootstrap class looks like this with Java:
@Configuration @EnableAutoConfiguration @ComponentScan public class SampleWebApplication { public static void main(String[] args) { SpringApplication.run(SampleWebApplication.class, args); } }
In scala, though I needed to provide two classes, one to specify the annotation and other to bootstrap the application, there may be better way to do this(blame it on my lack of Scala depth!) -
package mvctest import org.springframework.context.annotation.Configuration import org.springframework.boot.autoconfigure.EnableAutoConfiguration import org.springframework.context.annotation.ComponentScan import org.springframework.boot.SpringApplication @Configuration @EnableAutoConfiguration @ComponentScan class SampleConfig object SampleWebApplication extends App { SpringApplication.run(classOf[SampleConfig]); }
./gradlew build && java -jar build/libs/spring-boot-scala-web-0.1.0.jar
I have the entire git project available at this github location: https://github.com/bijukunjummen/spring-boot-scala-web
In conclusion, Scala can be considered a first class citizen for a Spring-boot based application and there is no special configuration required to get a Scala based Spring-boot application to work. It just works!
Published at DZone with permission of Biju Kunjummen, DZone MVB. See the original article here.
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