I was going to use ObjectHolders in my code to grab a couple items I needed to register models for.  It's client-only code, and stripped from the dedicated server.  The ObjectHolder injection still tries to do its thing and crashes.  Is there a way around this or can I not use ObjectHolders in this situation?

 

@SideOnly(Side.CLIENT)
@Mod.EventBusSubscriber(value = Side.CLIENT, modid = GradientMod.MODID)
public final class ModelManager {
  ...

  @GameRegistry.ObjectHolder("gradient:firepit_discriminator")
  private static final Item FIREPIT_DISCRIMINATOR = null;

  @GameRegistry.ObjectHolder("gradient:grinding_discriminator")
  private static final Item GRINDING_DISCRIMINATOR = null;

  @GameRegistry.ObjectHolder("gradient:mixing_discriminator")
  private static final Item MIXING_DISCRIMINATOR = null;

  ...
}

 

[11:42:48] [Server thread/ERROR] [minecraft/MinecraftServer]: Encountered an unexpected exception
java.lang.RuntimeException: java.lang.ClassNotFoundException: lordmonoxide.gradient.ModelManager
	at net.minecraftforge.registries.ObjectHolderRegistry.scanTarget(ObjectHolderRegistry.java:110) ~[ObjectHolderRegistry.class:?]
	at net.minecraftforge.registries.ObjectHolderRegistry.findObjectHolders(ObjectHolderRegistry.java:80) ~[ObjectHolderRegistry.class:?]
	at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:624) ~[Loader.class:?]
	at net.minecraftforge.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:99) ~[FMLServerHandler.class:?]
	at net.minecraftforge.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:333) ~[FMLCommonHandler.class:?]
	at net.minecraft.server.dedicated.DedicatedServer.init(DedicatedServer.java:128) ~[DedicatedServer.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:552) [MinecraftServer.class:?]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181]
Caused by: java.lang.ClassNotFoundException: lordmonoxide.gradient.ModelManager
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191) ~[launchwrapper-1.12.jar:?]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_181]
	at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_181]
	at net.minecraftforge.registries.ObjectHolderRegistry.scanTarget(ObjectHolderRegistry.java:104) ~[ObjectHolderRegistry.class:?]
	... 7 more
Caused by: net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerException: Exception in class transformer net.minecraftforge.fml.common.asm.transformers.SideTransformer@70101687 from coremod FMLCorePlugin
	at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:260) ~[forgeSrc-1.12.2-14.23.5.2772.jar:?]
	at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279) ~[launchwrapper-1.12.jar:?]
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176) ~[launchwrapper-1.12.jar:?]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_181]
	at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_181]
	at net.minecraftforge.registries.ObjectHolderRegistry.scanTarget(ObjectHolderRegistry.java:104) ~[ObjectHolderRegistry.class:?]
	... 7 more
Caused by: java.lang.RuntimeException: Attempted to load class lordmonoxide/gradient/ModelManager for invalid side SERVER
	at net.minecraftforge.fml.common.asm.transformers.SideTransformer.transform(SideTransformer.java:62) ~[forgeSrc-1.12.2-14.23.5.2772.jar:?]
	at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:256) ~[forgeSrc-1.12.2-14.23.5.2772.jar:?]
	at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279) ~[launchwrapper-1.12.jar:?]
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176) ~[launchwrapper-1.12.jar:?]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_181]
	at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_181]
	at net.minecraftforge.registries.ObjectHolderRegistry.scanTarget(ObjectHolderRegistry.java:104) ~[ObjectHolderRegistry.class:?]
	... 7 more

 

Wouldn’t it be logical to have references your items in your ModItems class?

Yes, and that's what I did to fix the issue, but I think this might be an oversight on Forge's part

Objectholders were never meant be used this way, which is why it crashes, you could submit a PR to Forge adding a check  if the class has a @SideOnly annotation in the object holder discovery logic though. @SideOnly should also not be used the way your using it though so...