First I delete the .sbt from my home-directory, then I make an empty project directory, and in that directory I create a build.sbt file:
echo 'ThisBuild / scalaVersion := "3.1.3"' > build.sbt
Then I run sbt console and at the console prompt attempt the following Class.forname() invocation, which produces the following ClassNotFoundException:
[info] welcome to sbt 1.7.1 (Debian Java 11.0.16)
Welcome to Scala 3.1.3 (11.0.16, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala> Class.forName("java.sql.Connection")
java.lang.ClassNotFoundException: java.sql.Connection
at dotty.tools.repl.AbstractFileClassLoader.findClass$$anonfun$1(AbstractFileClassLoader.scala:46
On the other hand, if I start the REPL with the plain-old scala command, then invoke the same forName() I see this:
Welcome to Scala 3.1.3 (11.0.16, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala> Class.forName("java.sql.Connection")
val res0: Class[?] = interface java.sql.Connection
So the same forName() invocation elicits different behavior in the sbt console versus the Scala REPL: a ClassNotFoundException in the former versus returning an instance of the Class class in the latter.
The sbt console also produces that ClassNotFoundException with any of the following lines in the build.sbt file:
classLoaderLayeringStrategy := ClassLoaderLayeringStrategy.AllLibraryJars
or
classLoaderLayeringStrategy := ClassLoaderLayeringStrategy.ScalaLibrary
or even
classLoaderLayeringStrategy := ClassLoaderLayeringStrategy.Flat
What is it about sbt that causes the exception, and how can sbt be made to succeed?
Related
With sbt everything is fine:
» sbt console
[info] Loading project definition from /repos/myrepo/project
[info] Set current project to bpavscan (in build file:/repos/myrepo/)
[info] Starting scala interpreter...
[info]
Welcome to Scala 2.11.8 (OpenJDK 64-Bit Server VM, Java 1.8.0_131).
Type in expressions for evaluation. Or try :help.
scala> import play.api.libs.json._
import play.api.libs.json._
scala>
But if I do it with the scala tool:
» scala
Welcome to Scala version 2.11.6 (OpenJDK 64-Bit Server VM, Java 1.8.0_131).
Type in expressions to have them evaluated.
Type :help for more information.
scala> import play.api.libs.json._
<console>:7: error: not found: value play
import play.api.libs.json._
^
scala>
I need to run a simple script, which I usually do with:
scala myscript.scala
But since now my script has a play dependency, I can not run it with scala anymore, since scala does not find play.
I need to either:
Be able to load the play framework with the simple scala tool
Be able to run a simple script with sbt: sbt run runs my project, which I do not want. I want to run a simple script (to try out some simple things)
sbt console with load the same console/REPL as of scala but with additional loaded dependencies defined in build.sbt. So before loading the console, all the dependent libraries are added. And this is reason you could import play libraries while using sbt console.
On the other hand scala starts the console with the libraries inside scala-package of the system. Thus needs additional jars being included inside the package for importing. For the above case if play library jar was included in scala directory then import play.api.libs.json._ should have worked for scala console too.
I've built a small test jar with Scala and SBT. If I put the classpath argument on the Scala REPL command line, it imports the package perfectly. However if I get into the shell and then add the classpath, it does not recognize the import. Being new to Scala this confuses me so I hope someone can explain. I'll try to provide enough information without going overboard.
scala -cp configparser_2.10-1.0.jar
Welcome to Scala version 2.10.4 (OpenJDK 64-Bit Server VM, Java 1.7.0_75).
Type in expressions to have them evaluated.
Type :help for more information.
scala> import com.oaktreepeak.util._
import com.oaktreepeak.util._
scala> val c = new OakConfig()
c: com.oaktreepeak.util.OakConfig = com.oaktreepeak.util.OakConfig#58d9a418
Now I'll wait and load the classpath to the jar after I'm in the shell:
scala
Welcome to Scala version 2.10.4 (OpenJDK 64-Bit Server VM, Java 1.7.0_75).
Type in expressions to have them evaluated.
Type :help for more information.
scala> :cp configparser_2.10-1.0.jar
Added '/home/*****/Dyn/projects/DynECT2/scala/common/ConfigParser/test-configs/configparser_2.10-1.0.jar'. Your new classpath is:
".:/home/*****/Dyn/projects/DynECT2/scala/common/ConfigParser/test-configs/configparser_2.10-1.0.jar"
Nothing to replay.
scala> import com.oaktreepeak.util._
<console>:7: error: object oaktreepeak is not a member of package com
import com.oaktreepeak.util._
^
scala>
Here is my build.sbt file:
name := "ConfigParser"
version := "1.0"
scalaVersion := "2.10.4"
organization := "com.oaktreepeak"
And the single Scala source file:
package com.oaktreepeak.util
import scala.io._
import scala.util.parsing.json._
class OakConfig {
var iRollupAfter: Int = -1;
def Load(sPath: String) {
val config = Source.fromFile(sPath).mkString
val json:Option[Any] =JSON.parseFull(config)
val map:Map[String,Any] = json.get.asInstanceOf[Map[String, Any]]
iRollupAfter = map.get("RollupAfter").get.asInstanceOf[Double].toInt
}
}
Anyone have any ideas or explanations?
Thanks
:cp was broken in Scala 2.10, and has been replaced with (a working) :require in Scala 2.11.
If you're new to Scala I would recommend using the latest, stable version of Scala, which currently is 2.11.6.
Also, as you're new to Scala, if you want to try things out from your project in the REPL (which is a great workflow) from sbt just run console, which will compile your code and give you REPL with all of Scala's classes, your projects classes and the classes for all your dependencies! No need to feed manually feed the REPL a classpath.
I run Windows 7.
I have java (a current enough version to run scala) and scala downloaded on my computer. I've set PATH so that when I type "scala" into the command prompt it sends me to the proper interface:
Welcome to Scala version 2.9.1.final (Java HotSpot(TM) 64-Bit Server VM, Java 1.7.0_51)
Type in expressions to have them evaluated.
Type :help for more information
However I can't execute the command "scala" or "scalac" on my test files.
scala> scala Hello
(console):8: error: object Hello is not a member of package scala
This makes me think I'm in the wrong directory. The file Hello.scala is saved in the home directory that I set PATH to.
However I get a different issue when I try to compile code.
scala> scalac Hello.scala
(console):1: error: ';' expected but '.' found.
I actually got my test file to work at one point... but I wasn't actually IN scala.
C:\scala-2.9.1.final\bin> scala Hello.scala
Hello world!
I'm not really sure how to proceed from here. If anyone has any ideas of what may be wrong I would greatly appreciate input.
It appears that you're trying to run & compile programs from within the Scala REPL (read-evaluate-print loop - a kind of Scala interpreter) and you cannot do that in the REPL. The REPL allows you to type in Scala statements and see them execute immediately. (If you're not sure how you entered the REPL, you probably just entered the command scala from the command line.) The REPL is useful for testing ideas, and for experimenting with Scala. For example:
C:\some\path> scala
Welcome to Scala version 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_91).
Type in expressions for evaluation. Or try :help.
scala> println ("Hello!")
Hello!
scala> val x = 10
x: Int = 10
scala> val y = x * 5
y: Int = 50
scala> sys.exit
C:\some\path>
However, the REPL isn't what you would use to compile & run Scala programs - you need to do that from the command line (or from a tool such as sbt). If you want to run your program directly from the command line, without using the REPL (that is, without being in Scala, as you put it) then you would need to do the following:
Firstly, compile your program using scalac:
C:\some\path> scalac Hello.scala
If that succeeds, you can then run the program with the scala command (which looks for a Hello.class file):
C:\some\path> scala Hello
(Here C:\some\path is the location of the files Hello.scala & Hello.class.)
Alternatively, as you have already discovered, you can run your Scala program as a script in the REPL. You can do this from the command line as follows (note the addition of the filetype .scala after Hello compared to the command above):
C:\some\path> scala Hello.scala
or from within the REPL:
scala> :load Hello.scala
Hope this helps!
You don't have to issue scala command when you're inside REPL. If you want to execute code from that file, load it:
here is what I have in Foo.scala
println("I'm foo")
Now I'm starting the REPL (and as you can see scala> is a sign that you're ALREADY into REPL and can start execute raw scala code):
Welcome to Scala version 2.10.3 (Java HotSpot(TM) 64-Bit Server VM, Java 1.7.0_25).
Type in expressions to have them evaluated.
Type :help for more information.
scala> :load Foo.scala
Loading Foo.scala...
I'm foo
When I run a worksheet in IntelliJ Idea 12 (sbt plugin, Scala project), I've got an error of:
> Failed to initialize compiler: class scala.reflect.BeanInfo not found.
** Note that as of 2.8 scala does not assume use of the java classpath.
** For the old behavior pass -usejavacp to scala, or if using a Settings
** object programatically, settings.usejavacp.value = true.
Everything what has to be set up, is setup: sbt, dependencies, etc, that is if run this project using sbt command line (compile, run), it will run successfully.
Of course, I ran sbt gen-idea.
What do I do?
My solution:
I created a new Scala project with IntelliJ IDEA and set the Scala home to the manually downloaded and unpacked Scala folder for Scala 2.10.2.
Now you can set the Scala compiler in the real project:
Switch to the real project, open the project structure settings and then Modules | your module name | Scala | compiler library. Switch to your new version.
Set the language level to 2.10.
Scala is installed and working fine.
scalacheck.jar is placed in the /bin .
I used the following command
$ scala -cp scalacheck.jar
After that, when i tried the below command,
scala> import org.scalacheck.Prop.forAll
I got the following error.
<console>:7: error: object scalacheck is not a member of package org
import org.scalacheck.Properties
^
I might have done some mistake in using scalacheck, please correct me and give the proper commands so that I can able to work with scalacheck in Ubuntu in interpreter mode.
Putting executable on the path isn't the same as jar being on the classpath, so your jar being in /bin didn't change anything.
Just use:
scala -cp path_to_your.jar
and you should be fine.
If for example, your scalachek.jar is in /bin then use:
scala -cp /bin/scalacheck.jar
edit:
Putting jars in /bin probably isn't the best idea.
You can use it like this:
kjozsa#walrus:~$ scala -version
Scala code runner version 2.9.2 -- Copyright 2002-2011, LAMP/EPFL
kjozsa#walrus:~$ locate scalacheck.jar
/usr/share/scala/lib/scalacheck.jar
kjozsa#walrus:~$ scala -cp /usr/share/scala/lib/scalacheck.jar
Welcome to Scala version 2.9.2 (OpenJDK 64-Bit Server VM, Java 1.7.0_03-icedtea).
Type in expressions to have them evaluated.
Type :help for more information.
scala> import org.scalacheck.Prop.forAll
import org.scalacheck.Prop.forAll
scala>