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How to run jar generated by package (possibly with other jars under lib)?
(3 answers)
Closed 2 years ago.
after packaging and executing a Scala application (build.sbt with version 2.12.0, but in fact having 2.13.3 installed) with SBT (version 1.3.13), I get the following error:
Exception in thread "main" java.lang.NoSuchMethodError: scala.Predef$.wrapRefArray([Ljava/lang/Object;)Lscala/collection/mutable/WrappedArray;
at org.example.GreetWorld$.printMessage(GreetWorld.scala:5)
The source file GreetWorld.scala that caused the error looks like this:
package org.example
object GreetWorld {
def printMessage(theMessage:String):Unit = {
println(s"${theMessage} from me")
}
}
The main file that is invoking the file above looks like this:
package org.example
object HelloWorld {
def main(args: Array[String]) = {
GreetWorld.printMessage("Hello")
}
}
Does anybody know the root cause? At first I thought it has to do with the SBT shell picking Java 11, but even after changing my Windows' JAVA_HOME to Java 8, I still get the same error. Compiling and running it in SBT Shell works fine. Only the JAR execution fails.
The error is pretty simple. When you run package you create a JAR which only contains the classes corresponding to your source code, nothing more. And your code depends on the Scala stdlib, so if you try to run it with java - jar it will fail with a class path error.
You have 4 solutions:
Run the JAR using scala directly. However, you need to use the same major version it was used to compile.
Put the Scala library jar in the classpath when running. This is basically the same as above. Thus again, you have to use the same major version.
Create an uber jar that already has the Scala stdlib (as well as any other dependency) in it, using sbt-assembly.
Create a native distributable that will set up everything for you, using sbt-native-packager.
For local development and testing option 1 is usually the best one.
For simple projects option 3 is, IMHO, the simplest alternative.
And for very complex projects option 4 is very popular.
I am trying to compile the scala/Play framework example application on my local machine, but I am getting compilation errors when trying to compile using the SBT console in IntelliJ:
error: scala.reflect.internal.MissingRequirementError: object java.lang.Object in compiler mirror not found.
I also got this message in the event log related to different SBT versions:
14:48 Started sbt shell with sbt version 0.13.18 instead of 0.13.11 configured by project.
Update sbt version
Disable version override
Any suggestions on how to fix this?
For the first error
error: scala.reflect.internal.MissingRequirementError: object java.lang.Object in compiler mirror not found.
You might want to try and ensure that you are using a compatible java version. Like #cbley suggested, try making you are using version 8 of the JDK.
For the second error
14:48 Started sbt shell with sbt version 0.13.18 instead of 0.13.11 configured by project.
Update sbt version
Disable version override
Its just suggesting you update the version of sbt (which is most likely declared in your build.properties file in a folder called project. You can just search for it by double tapping shift in IntelliJ. But you are safe to ignore it if you cloned some example repository as well.
check
I'm new to working with both IntelliJ and Scala, so I've been trying to set up a basic HelloWorld project using it. However once I try to load the project I'm met with two problems
I get an error saying there was an "Error while importing SBT project"
No 'src' folder appears on the project tree
I've seen similar problems here and here, but I still can't get the project to load properly.
For some reason this site doesn't let you post an image until you have 10 reputation, so here is a link to the error message I'm receiving http://i.imgur.com/vDZB6SA.png.
From the looks of it, it seems like it's unable to download the necessary dependencies, however I was able to download the scala plugin earlier, so I can't see why there would be a problem now.
I tried following the advice here on updating the proxy settings, but that doesn't work either.
Has anyone encountered a similar problem? I'm really stuck here on how to proceed.
EDIT 1:
Details on IntelliJ
IntelliJ IDEA 2016.2.3
Build #IC-162.1812.17, built on August 30, 2016
JRE: 1.8.0_65-b17 amd64
JVM: Java HotSpot(TM) 64-Bit Server VM by Oracle Corporation
Setting up the proejct:
I just followed an example and went to New Project > Scala > SBT > name project and finish. Then once it loads I get the error displayed in the picture above. The SBT version is 0.13.8 and the Scala version is 2.11.8
I am trying to develop an application using java opencv 3.0.0-beta using scala.
I am getting a runtime error:
java.lang.UnsatisfiedLinkError: java.lang.UnsatisfiedLinkError: org.opencv.imgcodecs.Imgcodecs.imread_1(Ljava/lang/String;)J
While researching the cause i have created the following simple application the exhibits similar behaviour:
import reflect._
import org.opencv.core.Core
import org.opencv.core.Mat
import org.opencv.core.CvType
import org.opencv.imgcodecs.Imgcodecs
object main extends Application {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME)
val what = "something.png"
val mat = Imgcodecs.imread(what)
Imgcodecs.imwrite("something_else.png", mat)
}
The major difference is that, if run as "sbt run" it performs as expected. if the appropriate lines are removed from the above the code fails in REPL.
I suspect that this issue is related to the original issue, but have no proof.
If i look at the memory map of the JVM in both cases i have the expected libs loaded.
If the code is inspected i find no definition of org.opencv.imgcodecs.Imgcodecs.imread_1
I am quite lost as to where to go next in diagnosing this issue.
Is there anyone who has come across this issue?
Thanks
i haven't used openCV3.0 yet, as it has major changes and breaks opencv 2.4.x code , are you supplying the library path to
sbt run
add
javaOptions in run += "-Djava.library.path=lib/opencv/"
to your build.sbt file or pass on cmd line
sbt run -Djava.library.path=lib/opencv/
opencv folder should have your files that gets generated along with your jar file
i have java bindins for 2.4.9 , 2.4.10 and 3.0.0 for java 7 and 8 in this git repo if you need them
git#gitlab.com:opencv/java_lib.git
I successfully implemented and ran several Scala tutorials in Eclipse using the Scala plugin. Then suddenly I tried to compile and run an example, and this error came up:
Exception in thread "main" java.lang.NoClassDefFoundError: hello/HelloWorld
Caused by: java.lang.ClassNotFoundException: hello.HelloWorld
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:315)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:330)
at java.lang.ClassLoader.loadClass(ClassLoader.java:250)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398)
After this point I could no longer run any Scala programs in Eclipse. I tried cleaning and rebuilding my project, closing and reopening my project, and closing and reopening Eclipse.
Eclipse version number 3.5.2 and Scala plugin 2.8.0
Here is the original code:
package hello
object HelloWorld {
def main(args: Array[String]){
println("hello world")
}
}
If you see this when you attempt to run as a Scala application then the most likely explanation is that your project didn't compile and no class files were generated. Please check whether or not that's the case: look in your project's output folder for hello/HelloWorld.class.
If your project didn't compile that could either be because there's an error which you've missed (and if this error isn't being reported in the Problems view that could be a bug, in which case please open a ticket on Trac) or because you've turned off automatic builds and not done a manual build of your project.
I had the same problem. Project doesn't compile but there are no errors highlighted and AFAIK the code is OK. It seems to be a problem with the Run Configurations.
Solution 1: Delete the existing Run Configuration for your object and create a new one
Solution 2: Create a new object and cut / paste all your code into that file
When running "clean" does not un-hose Eclipse, I next try saving my work, exiting Eclipse, and re-starting. That usually gets things going again, but not always. A few times I've had to update the Scala plugin with a more recent version (I'm using the latest nightly), to get things working again. I doubt that this worked because the new plugin happened to fix the bug, but rather expect that loading the new plugin gives the whole Eclipse-Scala
system a "total reset" that gets it unhosed.
I was getting this problem in a project that combined .java & .scala files.
The solution for me was:
Remove all .java files
Edit the scala code as needed so it compiles without them.
Add the .java files back in.
Edit the scala code back.
The other solutions given here didn't work for me. I tried: clean project, restarting Eclipse, closing-&-opening the project, creating a new .scala file. No joy.
I'm using Eclipse 3.7 (latest stable), Scala IDE 2.0.0 and Scala 2.9 on Ubuntu Linux 11.10.
The symptoms in my case were:
My project was working, but then it stopped compiling for no apparent reason. The IDE didn't show any compilation errors for .scala files, but there were no .class files in the output directory & I got a NoClassDefError if I tried to run anything.
If I created a deliberate error in a .scala file, that did get picked up as a compilation error.
The .java files were registering errors due to the missing scala classes.
I suppose there's probably a boot-strapping bug somewhere in the IDE plugin for .java/.scala mixes. I've done hybrid projects with this setup without problems, so it's only triggered in some situations. I don't know what the trigger is, but once triggered, there's no nice solution.
I had moved my one and only class/object/application to a package, but had not added the package declaration.
sbt compiled and ran fine; eclipse would not
Adding the package declaration at the top of the file fixed it.
Scala 2.8.3 plugin; no compile error
I encountered this error too but after doing the suggestions here (cleaning, deleting Run Configuration etc), I realized that I set the workspace wrongly that is why the class is not being found.
An indication that this is a problem is when the same error occurs when you try to compile a java project.
I encountered this error (compilation worked in sbt but failed in eclipse) when I created a new package object called "common". Deleting the package object in eclipse caused the compile error to go away. There was nothing in it.
I was using sbt-eclipse to build the eclipse project. I'm using scala eclipse 3.0.0-vfinal-20130326-1146-Typesafe.