Using Scala with MongoDB - java.lang.NoClassDefFoundError: com/mongodb/DBObject

Question

I created a simple project.

"sbt run" works fine.

After I run "sbt package" jar file appears, but it does not work.

$ scala target/scala-2.9.2/hello_2.9.2-0.1.jar

The following error occures:

java.lang.NoClassDefFoundError: com/mongodb/DBObject

Here are my files:

Hello.scala

package greeter
object Hello extends App {
    import com.mongodb.casbah.Imports._
    val mongoClient =  MongoClient()
    println("Connected to MongoDB")
    val collection = mongoClient("test")("foo")
    val doc = MongoDBObject("msg" -> "Hi from Scala!")
    collection.insert(doc)
    println("Doc inserted");
}

build.sbt

name := "hello"

mainClass := Some("greeter.Hello")

version := "0.1"

scalaVersion := "2.9.2"

libraryDependencies += "org.mongodb" % "casbah_2.9.2" % "2.5.0"

resolvers += "snapshots" at "https://oss.sonatype.org/content/repositories/snapshots"

resolvers += "releases"  at "https://oss.sonatype.org/content/groups/scala-tools"

Joel Arnold · Accepted Answer · 2013-02-08 19:02:39Z

1

You need to add the library dependencies to your classpath when running the scala command. Assuming you download all the libraries jars in a lib folder, you will need to run:

scala -cp "lib/*" target/scala-2.9.2/hello_2.9.2-0.1.jar

In build.sbt, use the following setting to automatically download all the jars in a lib_managed folder:

retrieveManaged := true

answered Feb 8, 2013 at 19:02

Joel Arnold

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4 Comments

un1t Over a year ago

Thank you. So I need to copy all jar files from lib_managed folder to lib folder? Is there a simple command for that, or do I need to use some tricky bash command? And how can I combine all those jars in one?

Joel Arnold Over a year ago

Actually you can just use the lib_managed folder directly: scala -cp "lib_managed/*" target/scala-2.9.2/hello_2.9.2-0.1.jar Or you can copy the whole folder with: cp -rf lib_managed lib

un1t Over a year ago

I tried -cp "lib_managed/*", but it does not work. The same error occures java.lang.NoClassDefFoundError: com/mongodb/DBObject. Than I copied all jars to lib filder and used -cp "lib/*", and it works.

Joel Arnold Over a year ago

Sorry, I forgot that the jars are not at the root of lib_managed. The best way to make a clean lib dir with all the jars is to create an empty lib dir: mkdir lib and then copy the jars: find lib_managed/ -name *.jar -exec cp {} lib/ \;

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