Importing .jar files into Scala environment - scala

Question

Even after reading: Scala, problem with a jar file, I'm still a bit confused. I am trying to import some packages into my Scala file, and the interpreter is not recognizing them even after adding to classpath.
One example:
I have the import statement:
import org.json4s._
I downloaded the .jar from here: http://mvnrepository.com/artifact/org.json4s/json4s-native_2.10/3.2.4
and added to the interpreter classpath using:
scala> :cp /Users/aspangher13/Downloads/json4s-native_2.10-3.2.4.jar
Scala acknowledges the classpath:
Your new classpath is: ".:/Users/aspangher13/Downloads/json4s-native_2.10-3.2.4.jar:/Users/aspangher13/Downloads/jna-3.5.2.jar"
But still throws this error:
<console>:7: error: object scalatra is not a member of package org
import org.json4s._
Can anyone see what I'm doing wrong? Thanks!!
And as a followup, does anyone know where to find the package: JsonAST._?

Answer 1

Go the simple and create a little sbt project.
First step - create a project
For your purposes you don't need a complex build. So just create two files:
./build.sbt
name := "name your project"
version := "0.1"
scalaVersion := "2.10.2" // or whatever you prefer
./project/build.properties
sbt.version=0.12.4
The just go to the project root folder and call sbt
Second step - add dependencies
Open your ./build.sbt file and add:
libraryDependency ++= Seq(
"org.scalatra" %% "scalatra" % "2.2.1",
"org.scalatra" %% "scalatra-scalate" % "2.2.1",
"org.scalatra" %% "scalatra-specs2" % "2.2.1" % "test",
"org.json4s" %% "json4s-native % "3.2.4",
"net.java.dev.jna" & "jna" & "3.5.2"
)
Step three - run the console
Don't forget to reload sbt with reload task, and then call console or console-quick task. This should work.
But there are easier ways to do this:
1) Use gitter8 - Scalatra gitter8 project
2) Read little into about Scalatra sbt dependencies

Answer 2

Still not sure how :cp works but if you execute
scala -classpath "list of jars colon separated"
then inside the REPL do your imports it should work
import org.json4s._
import org.xyz
However, when you try to use the classes you are likely to be missing transitive dependencies required by json4s and so we come back to the sbt example # 4lex1v describes, which will handle this. Creating a little project and running sbt console will indeed greatly simplify this.
Seems like the -classpath and :cp are primarily meant to make your code available in the shell and then only if you understand all of the transitive dependencies, or have none.