Error compiling Scalatra project

Seriously? Unsupported major.minor version 51.0 when compiling a Scalatra project? The complete error is “Caused by: java.lang.UnsupportedClassVersionError: org/eclipse/jetty/server/Handler : Unsupported major.minor version 51.0”. After some Googling I found the following statement “You are using different JDK versions to compile and run the application”. No way, that is not possible. Continue reading

sbt cannot find play-json_2.11 library

Grrrr, just cloned some of my code from Github to my laptop. I initially worked on this code on my desktop. When I tried to compile it in sbt I got the following error sbt.ResolveException: unresolved dependency: com.typesafe.play#play-json_2.11;2.3.0: not found. It had been a while since I worked on the code so I was puzzled. It turns out there are problems with the Typesafe repository. As a workaround the repository needs to be added as a resolver to the build.sbt file.

resolvers += "Typesafe Maven Repository" at "http://repo.typesafe.com/typesafe/maven-releases/"

After this it compiled nicely. Sweet. Happy coding 🙂

ClassNotFoundException when adding slf4j to Akka

When adding to a Akka project I got the following error java.lang.ClassNotFoundException: akka.event.slf4j.Slf4jLogger. I double checked my configuration and the Akka documentation. The documentation says the following:

Akka provides a logger for SL4FJ. This module is available in the ‘akka-slf4j.jar’. It has one single dependency; the slf4j-api jar. In runtime you also need a SLF4J backend, we recommend Logback.

No success. Continue reading

Adding the latest release of Akka to an SBT project

A quick note how to create a SBT project with the latest release of Akka.

Create a build.sbt file:

name := "ScalaAkkaTest"

organization := "<Your organisation name>"

version := "0.1.0-SNAPSHOT"

scalaVersion := "2.11.2"

resolvers += "Typesafe Repository" at "http://repo.typesafe.com/typesafe/releases/"

libraryDependencies += "com.typesafe.akka" %% "akka-actor" % "2.3.6"

Continue reading

To compile XML syntax, the scala.xml package must be on the classpath

I was creating a servlet using Scala and got the following error message “To compile XML syntax, the scala.xml package must be on the classpath”. It turns out that Scala-XML has been factored out into a separate library as of Scala 2.11, so it is not included in Scala projects by default. So the dependency needs to be include in the project build.sbt using the following statement:

libraryDependencies += "org.scala-lang.modules" %% "scala-xml" % "1.0.2"

Note as always you should check that there isn’t a newer version available of the library. How? Google is your friend 🙂

maven org.scala-lang.modules scala-xml

Happy coding!