Scala newb here (it's my 2nd day of using it). I want to get log4j logging working in my Scala script. The script and the results are below, any ideas as to what's going wrong?
[sean#ibmp2 pybackup]$ cat backup.scala
import org.apache.log4j._
val log = LogFactory.getLog()
log.info("started backup")
[sean#ibmp2 pybackup]$ scala -cp log4j-1.2.16.jar:. backup.scala
/home/sean/projects/personal/pybackup/backup.scala:1: error: value apache is not a member of package org
import org.apache.log4j._
^
one error found
I reproduce it under Windows: delimiter of '-classpath' must be ';' there (not ':'). Are you use cygwin or some sort of unix emulator?
But Scala script works anywhere without current dir in classpath. Try to use:
$ scala -cp log4j-1.2.16.jar backup.scala
JFI: LogFactory is a class of slf4j library (not log4j).
UPDATE
Another possible case: broken jar in classpath, maybe during download or something else. Scala interpreter does report only about unavailable member of the package.
$ echo "qwerty" > example.jar
$ scala -cp example.jar backup.scala
backup.scala:1: error: value apache is not a member of package org
...
Need to inspect content of the jar-file:
$ jar -tf log4j-1.2.16.jar
...
org/apache/log4j/Appender.class
...
Did you remember to put log4j.jar in your classpath?
Had Similar issue when started doing Scala Development using Eclipse, doing a clean build solved the problem.
Guess the Scala tools are not matured et.
Instead of using log4j directly, you might try using Configgy. It's the Scala Way™ to work with log4j, as well as configuration files. It also plays nicely with SBT and Maven.
I asked and answered this question myself, have a look:
Put it under src/main/resources/logback.xml. It will be copied to the right location when SBT is doing the artifact assembly.
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.
:cp seems to only accept a single entry
scala> :cp /usr/lib/hadoop/*:/usr/lib/hadoop/lib/*:/usr/lib/hbase/*:/usr/lib/hbase/lib/*:
/home/sboesch/spark-master/lib_managed/jars/*:/home/sboesch/spark-master/lib_managed/bundles/*:
The path '/usr/lib/hadoop/*:/usr/lib/hadoop/lib/*:/usr/lib/hbase/*:/usr/lib/hbase/lib/*:/home/sboesch/spark-master/lib_managed/jars/*:/home/sboesch/spark-master/lib_managed/bundles/*:'
doesn't seem to exist.
Any thoughts on how to do this when already in the REPL. Yes I know how to set it up from outside the REPL :
CLASSPATH=/usr/lib/hadoop/*:/usr/lib/hadoop/lib/*:/usr/lib/hbase/*:/usr/lib/hbase/lib/*
:/home/sboesch/spark-master/lib_managed/jars/*:
/home/sboesch/spark-master/lib_managed/bundles/*: scala
EDIT It seems the intent were not clear. I am working on code in the REPL. Then have a new snippet of code that requires a few classpath entries. It is a ONE OFF affair: so I do not want to add to build.sbt or to the scala/lib dir , etc. I did not receive any answer really satisifying this use case, but awarded the best efforts anyways.
scala -cp "path1:path2" now seems to work.
scala -version Picked up _JAVA_OPTIONS: -Xms512m -Xmx4096m
-XX:MaxPermSize=1024m -XX:ReservedCodeCacheSize=128m Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=1024m; support
was removed in 8.0 Scala code runner version 2.11.8 -- Copyright
2002-2016, LAMP/EPFL
The help text for :cp says:
:cp <path> add a jar or directory to the classpath
So I'm guessing there's no exact way for you to get that. I'd use this:
:load <path> interpret lines in a file
I confirmed that it works for REPL commands as well as Scala code.
Addendum:
If you use SBT then all your projects dependencies are in the class-path for the REPL launched by SBT's console task.
A quick and dirty approach, add a link from $SCALA_HOME/lib/ to a folder with additional jar files. Then from REPL you can import packages of interest.
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.
(Relative beginner here, please be gentle...)
I've got a Scala program that I can build with sbt. I can (from within sbt) run compile and test-compile with no errors. I've defined a package by putting package com.mycompany.mypackagename at the top of several .scala files. When I do console to get a Scala REPL, this happens:
scala> import com.mycompany.mypackagename._
<console>:5: error: value mypackagename is not a member of package com.mycompany
import com.mycompany.mypackagename._
Any variation of this also fails. When I just do import com.mycompany I get no problems.
I thought that running the Scala console from within sbt would properly set the classpath based on the current projects? What (completely obvious) thing am I missing?
I ran into this same problem, and then I realized I was running scala 2.10.0 on commandline, and IDEA was using Scala 2.9.2. So the fix was to change both to use the same version, and:
sbt clean
What will happen if you import actual class name instead of wildcard.
import com.mycompany.mypackagename.ActualClassName
Im trying to put together a simple ant build file for compiling a scala project (scala 2.7.6)...
I have everything working correctly except that its bringing up the
"fatal error: class java.lang.Object not found." both the scalac and scala libs are all in the project folder, so Im refering to them relativelly to the project root.
Im hoping that someone could help with which command line scalac option I can use to point the compiler towards the java core lib (if thats what it needs). Im hoping not to use any environemnt variables, and instead have the needed java libs in my project root folder...
that way I can have everything needed to compile movable with the project, and not need any setup for others to be able to compile
thank you
Scala 2.7.6 is a broken release.
Please upgrade to 2.7.7
Also, do you have javac on PATH and JAVA_HOME set?