Say, I have an eclipse project located in D:\DanHenderson\scala\MyProject. MyProject has 2 directories: src and bin. In src I have scala code itself, it might be some classes or an application. So how can I use those classes or run whole application from command line? I.e., there is a file with class A, and I want to have a possibility to type val a = new A in command line. How can I do this?
By command line I assume you mean the Scala REPL. Add the directory of your class files to the classpath when starting the Scala REPL:
scala -classpath "path to some dir where your .class files reside"
Note that if your project relies on some libraries then those need to be on the classpath as well.
Related
I can't seem to get this to work, so i have tried what's probably the most straightforward case--ie, retrieve the jar file and into a given directory then start the scala REPL from that directory--still no luck.
I know the jar files are fine and correctly references (eg, i can access them from project directories via eclipse/scala ide)
I also know that my import statements (one is shown below) are valid.
cd ~/my_scala_jars
retrieve the artifact from the maven repo
wget -q -nd -np -r \
http://repo1.maven.org/maven2/org/scalaz/scalaz-core_2.12.0-M1/7.1.2/scalaz-core_2.12.0-M1-7.1.2.jar
start the scala REPL and add the jar to the REPL classpath:
scala -cp scalaz-core_2.12.0-M1-7.1.2.jar
scala> import scalaz.stream.io
<console>:7: error: object stream is not a member of package scalaz
import scalaz.stream.io
in case it's useful, trying this with different jars (that i downloaded as i showed with scalaz above) will sometimes cause the REPL to throw a not found error instead
scala> import breeze.linalg._
<console>:7: error: not found: value breeze
import breeze.linalg._
it seems to me that the REPL should recognize these jars because the directory has been added to my CLASSPATH, but also because i believe the current directory is also added to the classpath (at least during the REPL session)--and still both fail.
I am not sure why the jar files are not picked up as I haven't really tried to do that. What I do, and find useful, is to create a number of build.sbt files for specific purposes, e.g. for working with a specific suite of libraries at a REPL.
If you do this, and then launch a REPL using the command sbt console, from the directory containing the appropriate build.sbt, then you can have a console with the libraries you want available on the classpath to that console.
This might not be ideal, but it does work and I find it quite useful.
I have Activator installed. Which means I have a full SBT on my system. I don't want to create a brand new activator project. All I want to do is compile a single scala file as we used to do with the scalac command. How can I do this please? Thanks.
You go into the directory containing your scala file and type "sbt compile" on the command line.
To run the program, you type "sbt run"
see also
http://www.scala-sbt.org/0.13/tutorial/Hello.html
I am able to compile scala programs using scalac in terminal but I get the warning.
Charless-Macintosh:src Charles$ scalac hello.scala
Charless-Macintosh:src Charles$ scala HelloWorld
No such file or class on classpath: HelloWorld
Is this to do with .profile on scala. I'm pretty confused as to what is happening. Many thanks
The current directory is typically not in the classpath by default. So you need to give explicitly:
$ scala -cp . HelloWorld
The problem is that you have set the CLASSPATH environment variable.
From > man scalac:
The default class path is the current directory. Setting the CLASSPATH variable or using the -classpath command-line option overrides that default, so if you want to include the current directory in the search path, you must include "." in the new settings.
When you have the CLASSPATH variable set, scala will not include the current directory in its search, you must explicitly add it. This is why scala -cp . HelloWorld works.
To verify, perform echo CLASSPATH and it should give some non-empty string. Check your .bashrc/.zshrc files for any export CLASSPATH=... and remove these lines.
This was also happening to me but I think the better solution is to modify the CLASSPATH variable to include the current directory in addition to what you already had. e.g.
export CLASSPATH=.:$CLASSPATH
Now, you can simply use scala HelloWorld without that additional argument.
I'm trying to import com.lambdaworks.crypto.SCryptUtil (from crypto) in the Scala REPL. I'm running the REPL from the Java directory containing com/lambdaworks/crypto.
The REPL can't find com.lambdaworks.crypto.SCryptUtil, but it can autocomplete up to com.lambdaworks.crypto but can't find anything after that.
When I used the REPL in the IntelliJ IDEA after including the package in my project, I was able to find the SCryptUtil class.
Am I missing some classpath parameters that are required for import?
The REPL won't compile the Java code for you—it's only autocompleting that far because it's aware of the directory structure, but once it gets to the crypto directory it won't find any class files.
You can see this more dramatically by moving up a directory and opening a new REPL—you'll be able to autocomplete import java.com.lambdaworks.crypto, even though that's obviously not a real package hierarchy.
In this case you can move to the project root, run mvn compile to compile the Java code, and then start the REPL like this (still in the project root):
scala -classpath target/classes
Now you can import com.lambdaworks.crypto.SCryptUtil.
This only works because the project doesn't have any runtime dependencies, though—in other cases you may need either to add other things to the classpath, to build a JAR with the dependencies baked in (e.g. with the Maven Assembly plugin), or to use the mvn scala:console goal of the Maven Scala plugin.
The answer: Making stand-alone jar with Simple Build Tool seems like what I need, but it did not have enough information for me, so this is a followup.
(1) How do I adapt the answer to my need? I don't understand what would need to be changed.
(2) What command do I run to create the standalone jar?
(3) Where can I find the jar after it has been created?
What I've tried:
Pasting the code in the linked answer verbatim into my: project/build/dsg.scala file. The file now has a
class ForkRun(info: ProjectInfo) extends DefaultProject(info)
(from before, used for running projects in a separate VM from SBT) and the new:
trait AssemblyProject extends BasicScalaProject
from the linked answer.
I also tried pasting the body (all defs and the lazy val of the AssemblyProject into the body of ForkRun.
To create a jar I ran package at the SBT prompt and get:
[info] Packaging ./target/scala_2.8.1/dsg_2.8.1-1.0.jar ...
[info] Packaging complete.
So I tried running the dsg_2.8.1-1.0.jar from the shell via:
java -jar dsg_2.8.1-1.0.jar
But I get:
Failed to load Main-Class manifest attribute from
dsg_2.8.1-1.0.jar
Could this be caused by having multiple entry points into my project? I select from a list when I execute run from the SBT prompt. Perhaps I need to specify the default when creating the package?
Here's a writeup I did on one way to make an executable jar with SBT:
http://janxspirit.blogspot.com/2011/01/create-executable-scala-jar-with-sbt.html
sbt-assembly is a sbt plugin to create a standalone jar of Scala sbt project with all of its dependencies.
Refer this post for more details with an example.