java.lang.NoClassDefFoundError: jdk/nashorn/api/scripting/NashornScriptEngineFactory

Question

I want to code a Minecraft mod in 1.16.3. I have already make a mod in 1.12.2 but I didn't have this problem. I just download the 1.16.3 forge Mdk and build it for eclipse (with 'gradlew eclipse' in cmd) but when I try to run the mod (with 'runClient.launch'). It gives an error:

java.lang.NoClassDefFoundError: jdk/nashorn/api/scripting/NashornScriptEngineFactory.

I tried to modify the main file and packages to support the not necessary code but when I start. It gives me the same error.

My main file:

package fr.luzog78.newmod;

import net.minecraft.block.Blocks;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent;
import net.minecraftforge.fml.event.lifecycle.FMLCommonSetupEvent;
import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

@Mod("newmod")
public class NewMod {
    private static final Logger LOGGER = LogManager.getLogger();

    public NewMod() {
        FMLJavaModLoadingContext.get().getModEventBus().addListener(this::setup);
        FMLJavaModLoadingContext.get().getModEventBus().addListener(this::doClientStuff);

        MinecraftForge.EVENT_BUS.register(this);
    }

    private void setup(final FMLCommonSetupEvent event) {
        LOGGER.info("HELLO FROM PREINIT");
        LOGGER.info("DIRT BLOCK >> {}", Blocks.DIRT.getRegistryName());
    }

    private void doClientStuff(final FMLClientSetupEvent event) {
    }

//    @SubscribeEvent
//    public void onServerStarting(FMLServerStartingEvent event) {
//        // do something when the server starts
//        LOGGER.info("HELLO from server starting");
//    }
//
//    // You can use EventBusSubscriber to automatically subscribe events on the contained class (this is subscribing to the MOD
//    // Event bus for receiving Registry Events)
//    @Mod.EventBusSubscriber(bus=Mod.EventBusSubscriber.Bus.MOD)
//    public static class RegistryEvents {
//        @SubscribeEvent
//        public static void onBlocksRegistry(final RegistryEvent.Register<Block> blockRegistryEvent) {
//            // register a new block here
//            LOGGER.info("HELLO from Register Block");
//        }
//    }
}

And the stack trace:

Exception in thread "main" [13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]: java.lang.NoClassDefFoundError: jdk/nashorn/api/scripting/NashornScriptEngineFactory
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at net.minecraftforge.coremod.CoreModEngine.loadCoreMod(CoreModEngine.java:48)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at net.minecraftforge.coremod.CoreModProvider.addCoreMod(CoreModProvider.java:12)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:274)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:497)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at net.minecraftforge.fml.loading.LoadingModList.addCoreMods(LoadingModList.java:85)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at net.minecraftforge.fml.loading.moddiscovery.ModDiscoverer.discoverMods(ModDiscoverer.java:129)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at net.minecraftforge.fml.loading.FMLLoader.beginModScan(FMLLoader.java:213)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at net.minecraftforge.fml.loading.FMLServiceProvider.runScan(FMLServiceProvider.java:107)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at cpw.mods.modlauncher.TransformationServiceDecorator.runScan(TransformationServiceDecorator.java:114)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at cpw.mods.modlauncher.TransformationServicesHandler.lambda$runScanningTransformationServices$8(TransformationServicesHandler.java:115)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:271)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.HashMap$ValueSpliterator.forEachRemaining(HashMap.java:1766)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at cpw.mods.modlauncher.TransformationServicesHandler.runScanningTransformationServices(TransformationServicesHandler.java:116)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at cpw.mods.modlauncher.TransformationServicesHandler.initializeTransformationServices(TransformationServicesHandler.java:63)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at cpw.mods.modlauncher.Launcher.run(Launcher.java:76)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at cpw.mods.modlauncher.Launcher.main(Launcher.java:66)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1048]:   at net.minecraftforge.userdev.LaunchTesting.main(LaunchTesting.java:105)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1057]: Caused by: java.lang.ClassNotFoundException: jdk.nashorn.api.scripting.NashornScriptEngineFactory
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1057]:   at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:606)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1057]:   at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:168)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1057]:   at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
[13:16:47] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1057]:   ... 33 more

Answer 1

It seems the Minecraft code you are using depends on the Nashorn scripting engine. Nashorn was removed from the JDK in Java 15, which it seems you are running.

Downgrade to JDK 14 or an earlier version.

Answer 2

Solution

---

• Nashorn was removed from the JDK in Java 15 ( https://openjdk.java.net/jeps/372 )
• You need to launch with Java 1.8 (to avoid UnsupportedClassVersionError)
• So you have to :
  1. Go to Project Properties >> Java compiler >> Compiler >> compilance level and modify to Java SE - 1.8
  2. Modify your path (put jdk1.8)
  3. And if that not works, go to Preferences >> Java >> Installed JREs and Preferences >> Java >> Installed JREs >> Execution Environments

---

Thanks to @LukeWoodward !!