Earlier I had blogged about using Scala with Spring Boot and how the combination just works. There was one issue with the previous approach though – the only way to run the earlier configuration was to build the project into a jar file and run the jar file.
./gradlew build java -jar build/libs/spring-boot-scala-web-0.1.0.jar
Spring boot comes with a gradle based plugin which should have allowed the project to run with a “gradle bootRun” command, this unfortunately gives an error for scala based projects.
A good workaround is to use sbt for building and running Spring-boot based projects. The catch though is that with gradle and maven, the versions of the dependencies would have been managed through a parent pom, now these have to be explicitly specified. This is how a sample sbt build file with the dependencies spelled out looks:
name := "spring-boot-scala-web" version := "1.0" scalaVersion := "2.10.4" sbtVersion := "0.13.1" seq(webSettings : _*) libraryDependencies ++= Seq( "org.springframework.boot" % "spring-boot-starter-web" % "1.0.2.RELEASE", "org.springframework.boot" % "spring-boot-starter-data-jpa" % "1.0.2.RELEASE", "org.webjars" % "bootstrap" % "3.1.1", "org.webjars" % "jquery" % "2.1.0-2", "org.thymeleaf" % "thymeleaf-spring4" % "2.1.2.RELEASE", "org.hibernate" % "hibernate-validator" % "5.0.2.Final", "nz.net.ultraq.thymeleaf" % "thymeleaf-layout-dialect" % "1.2.1", "org.hsqldb" % "hsqldb" % "2.3.1", "org.springframework.boot" % "spring-boot-starter-tomcat" % "1.0.2.RELEASE" % "provided", "javax.servlet" % "javax.servlet-api" % "3.0.1" % "provided" ) libraryDependencies ++= Seq( "org.apache.tomcat.embed" % "tomcat-embed-core" % "7.0.53" % "container", "org.apache.tomcat.embed" % "tomcat-embed-logging-juli" % "7.0.53" % "container", "org.apache.tomcat.embed" % "tomcat-embed-jasper" % "7.0.53" % "container" )
Here I am also using xsbt-web-plugin which is plugin for building scala web applications.
xsbt-web-plugin also comes with commands to start-up tomcat or jetty based containers and run the applications within these containers, however I had difficulty in getting these to work.
What worked is the runMain command to start up the Spring-boot main program through sbt:
runMain mvctest.SampleWebApplication
and xsbt-web-plugin allows the project to be packaged as a war file using the “package” command, this war deploys and runs without any issues in a standalone tomcat container.
Here is a github project with these changes: https://github.com/bijukunjummen/spring-boot-scala-web.git
| Reference: | Spring Boot and Scala with sbt as the build tool from our JCG partner Biju Kunjummen at the all and sundry blog. |
