GenElectrovise

We need more information - this may not be a problem with Forge. Please post debug.log This is found in ".minecraft/run/logs/debug.log"

How did you set up your workspace thus far?

And the teletype button as well... I've had to resort to putting class names in bold! But I suppose all legends must pass... dark times... At least we can still (sort of) get them!

When I last regularly used this forum, the spoiler button (next to the code block and emojis) was really helpful.... How long has it been gone

Where did you put this?

Read the EAQ! We need logs! Have you done other research? https://forums.minecraftforge.net/topic/20-rules-and-eaq-read-first-or-you-will-get-banned/

Look at how entities in general are moved. The player is just an entity. Entities have velocity variables in them, which you can use to move them. Look through some entity AI goals, and in entity navigators to see these in actions. The Minecraft class has a reference to the client player, however you may need to send a packet to the server (or something similar) in order for the server to get the memo.

I am trying to add my OvergroundShrineFeature to different Biomes. For reference, I have been using the RuinedPortalStructure and its various dependants (i.e. RuinedPortalFeature and its configurations) for reference. I am able to register the Structure, and I am able to register its StructureFeatures. When I use a /locate magiksmostevile:overground_shrine command in game (which it suggests to autocomplete), I get the message "The structure could not be found", as if it were simply very far away, however as I move around, I receive a lot of errors saying that there is either a error reading or writing NBT data. I tracked the error back to writing the References tag (something is null but I can't tell what), but it doesn't always fail there. I can't view some of the variables in debug mode on my IDE, so I can't see exactly what is being written when an exception is thrown... To me, this suggests that I have taken something from the vanilla code that I should not have done, and that there is a better, more "Forge-y", way to handle this. How should I be managing structure generation? Thanks! Edit: I should add that my Structure.Start class is never called, nor is any other part of the building process: I know because I put breakpoints on them all and nothing is triggered after the structure is added to biomes. Perhaps these NBT errors occur when the game tries to load my structure from NBT, it fails, and terminates the building? ==== Active GitHub branch: https://github.com/GenElectrovise/MagiksMostEvile/tree/feature/1.16.4/reinstate_shrines World-Gen package: https://github.com/GenElectrovise/MagiksMostEvile/tree/feature/1.16.4/reinstate_shrines/src/main/java/genelectrovise/magiksmostevile/common/world/gen DeferredRegistry: https://github.com/GenElectrovise/MagiksMostEvile/blob/feature/1.16.4/reinstate_shrines/src/main/java/genelectrovise/magiksmostevile/common/core/registry/EvileDeferredRegistry.java ==== Register Structure: public static final DeferredRegister<Structure<?>> STRUCTURES = DeferredRegister.create(ForgeRegistries.STRUCTURE_FEATURES, MagiksMostEvile.MODID); public static final RegistryObject<Structure<OvergroundShrineFeatureConfig>> OVERGROUND_SHRINE = STRUCTURES.register("overground_shrine", () -> new OvergroundShrineStructure()); Register StructureFeatures: // Called in FMLCommonSetupEvent // Register a different one for each EnumFeatureLocation so that it is generated differently in each case // Default OVERGROUND_SHRINE_DEFAULT = StructureAspectRegistrationManager.registerStructureFeature( MagiksMostEvile.MODID + ":overground_shrine/default", EvileDeferredRegistry.OVERGROUND_SHRINE.get() .withConfiguration(new OvergroundShrineFeatureConfig(EnumFeatureLocation.DEFAULT))); Error message (loading NBT only): [28Dec2020 13:15:51.534] [Server thread/ERROR] [net.minecraft.world.server.ChunkManager/]: Couldn't load chunk [-22, 9] java.util.concurrent.CompletionException: net.minecraft.crash.ReportedException: Loading NBT data at java.util.concurrent.CompletableFuture.reportJoin(CompletableFuture.java:375) ~[?:1.8.0_241] at java.util.concurrent.CompletableFuture.join(CompletableFuture.java:1947) ~[?:1.8.0_241] at net.minecraft.world.chunk.storage.IOWorker.func_227090_a_(IOWorker.java:64) ~[forge:?] at net.minecraft.world.chunk.storage.ChunkLoader.readChunk(ChunkLoader.java:57) ~[forge:?] at net.minecraft.world.server.ChunkManager.loadChunkData(ChunkManager.java:831) ~[forge:?] at net.minecraft.world.server.ChunkManager.lambda$chunkLoad$14(ChunkManager.java:493) ~[forge:?] at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1604) ~[?:1.8.0_241] at net.minecraft.util.concurrent.ThreadTaskExecutor.run(ThreadTaskExecutor.java:139) ~[forge:?] at net.minecraft.world.server.ServerChunkProvider$ChunkExecutor.run(ServerChunkProvider.java:512) ~[forge:?] at net.minecraft.util.concurrent.ThreadTaskExecutor.driveOne(ThreadTaskExecutor.java:109) ~[forge:?] at net.minecraft.world.server.ServerChunkProvider$ChunkExecutor.driveOne(ServerChunkProvider.java:520) ~[forge:?] at net.minecraft.world.server.ServerChunkProvider.driveOneTask(ServerChunkProvider.java:270) ~[forge:?] at net.minecraft.server.MinecraftServer.driveOneInternal(MinecraftServer.java:746) ~[forge:?] at net.minecraft.server.MinecraftServer.driveOne(MinecraftServer.java:735) ~[forge:?] at net.minecraft.util.concurrent.ThreadTaskExecutor.drainTasks(ThreadTaskExecutor.java:97) ~[forge:?] at net.minecraft.server.MinecraftServer.runScheduledTasks(MinecraftServer.java:720) ~[forge:?] at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:667) ~[forge:?] at net.minecraft.server.MinecraftServer.lambda$startServer$0(MinecraftServer.java:233) ~[forge:?] at java.lang.Thread.run(Thread.java:748) [?:1.8.0_241] Caused by: net.minecraft.crash.ReportedException: Loading NBT data at net.minecraft.nbt.CompoundNBT.loadNBT(CompoundNBT.java:526) ~[forge:?] at net.minecraft.nbt.CompoundNBT.access$200(CompoundNBT.java:31) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:53) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:40) ~[forge:?] at net.minecraft.nbt.CompoundNBT.loadNBT(CompoundNBT.java:520) ~[forge:?] at net.minecraft.nbt.CompoundNBT.access$200(CompoundNBT.java:31) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:53) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:40) ~[forge:?] at net.minecraft.nbt.CompoundNBT.loadNBT(CompoundNBT.java:520) ~[forge:?] at net.minecraft.nbt.CompoundNBT.access$200(CompoundNBT.java:31) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:53) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:40) ~[forge:?] at net.minecraft.nbt.CompressedStreamTools.read(CompressedStreamTools.java:129) ~[forge:?] at net.minecraft.nbt.CompressedStreamTools.read(CompressedStreamTools.java:99) ~[forge:?] at net.minecraft.nbt.CompressedStreamTools.read(CompressedStreamTools.java:92) ~[forge:?] at net.minecraft.world.chunk.storage.RegionFileCache.readChunk(RegionFileCache.java:51) ~[forge:?] at net.minecraft.world.chunk.storage.IOWorker.lambda$func_227090_a_$2(IOWorker.java:54) ~[forge:?] at net.minecraft.world.chunk.storage.IOWorker.lambda$null$8(IOWorker.java:99) ~[forge:?] at net.minecraft.util.concurrent.ITaskQueue$RunnableWithPriority.run(ITaskQueue.java:61) ~[forge:?] at net.minecraft.util.concurrent.DelegatedTaskExecutor.driveOne(DelegatedTaskExecutor.java:88) ~[forge:?] at net.minecraft.util.concurrent.DelegatedTaskExecutor.driveWhile(DelegatedTaskExecutor.java:132) ~[forge:?] at net.minecraft.util.concurrent.DelegatedTaskExecutor.run(DelegatedTaskExecutor.java:100) ~[forge:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_241] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_241] ... 1 more Caused by: java.io.EOFException at java.io.DataInputStream.readUnsignedShort(DataInputStream.java:340) ~[?:1.8.0_241] at java.io.DataInputStream.readUTF(DataInputStream.java:589) ~[?:1.8.0_241] at java.io.DataInputStream.readUTF(DataInputStream.java:564) ~[?:1.8.0_241] at net.minecraft.nbt.CompoundNBT.readKey(CompoundNBT.java:515) ~[forge:?] at net.minecraft.nbt.CompoundNBT.access$100(CompoundNBT.java:31) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:50) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:40) ~[forge:?] at net.minecraft.nbt.CompoundNBT.loadNBT(CompoundNBT.java:520) ~[forge:?] at net.minecraft.nbt.CompoundNBT.access$200(CompoundNBT.java:31) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:53) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:40) ~[forge:?] at net.minecraft.nbt.CompoundNBT.loadNBT(CompoundNBT.java:520) ~[forge:?] at net.minecraft.nbt.CompoundNBT.access$200(CompoundNBT.java:31) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:53) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:40) ~[forge:?] at net.minecraft.nbt.CompoundNBT.loadNBT(CompoundNBT.java:520) ~[forge:?] at net.minecraft.nbt.CompoundNBT.access$200(CompoundNBT.java:31) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:53) ~[forge:?] at net.minecraft.nbt.CompoundNBT$1.readNBT(CompoundNBT.java:40) ~[forge:?] at net.minecraft.nbt.CompressedStreamTools.read(CompressedStreamTools.java:129) ~[forge:?] at net.minecraft.nbt.CompressedStreamTools.read(CompressedStreamTools.java:99) ~[forge:?] at net.minecraft.nbt.CompressedStreamTools.read(CompressedStreamTools.java:92) ~[forge:?] at net.minecraft.world.chunk.storage.RegionFileCache.readChunk(RegionFileCache.java:51) ~[forge:?] at net.minecraft.world.chunk.storage.IOWorker.lambda$func_227090_a_$2(IOWorker.java:54) ~[forge:?] at net.minecraft.world.chunk.storage.IOWorker.lambda$null$8(IOWorker.java:99) ~[forge:?] at net.minecraft.util.concurrent.ITaskQueue$RunnableWithPriority.run(ITaskQueue.java:61) ~[forge:?] at net.minecraft.util.concurrent.DelegatedTaskExecutor.driveOne(DelegatedTaskExecutor.java:88) ~[forge:?] at net.minecraft.util.concurrent.DelegatedTaskExecutor.driveWhile(DelegatedTaskExecutor.java:132) ~[forge:?] at net.minecraft.util.concurrent.DelegatedTaskExecutor.run(DelegatedTaskExecutor.java:100) ~[forge:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_241] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_241] ... 1 more

Hmmm... strange. It seems to be working for me right now? By my researching withFeature(feature) both returns the builder, and adds the feature. I'll try changing that and see how that works.

I've resolved the error: It was resulting from a NullPointerException while I was adding my features to biomes, which was concealed behind a resulting exception which was traced back to the mouseClickEventHandler which was triggered when I loaded the world. I was adding my features to a static ConfiguredFeature<?,?> [ ], before they were actually loaded, with the expectation that the array references would be updated as well, but I guess concurrency decided that wouldn't happen. Now the final call of my event handler populates the arrays and everything works fine. My new code is: OreFeaures.java public static ConfiguredFeature<?, ?>[] OVERWORLD_ORES; public static ConfiguredFeature<?, ?>[] NETHER_ORES; public static ConfiguredFeature<?, ?>[] END_ORES; @SubscribeEvent //Subbed to MOD public static void createConfiguredOreFeatures(FMLCommonSetupEvent event) { MagiksMostEvile.LOGGER.debug("Creating MME configured ore features"); // Amethyst Ore Overworld AMETHYST_ORE_OVERWORLD = Registry.register( // WorldGenRegistries.CONFIGURED_FEATURE, // "amethyst_ore_overworld_generation", // Feature.ORE.withConfiguration( // new OreFeatureConfig( // new TagMatchRuleTest(ModdedTags.AMETHYST_ORE_SPAWNABLE), // EvileDeferredRegistry.AMETHYST_ORE_OVERWORLD.get().getDefaultState(), // 7)) // .withPlacement(Placement.DEPTH_AVERAGE.configure( // new DepthAverageConfig(32, 32))) // .range(16)); // applyToLists(); } private static void applyToLists() { OVERWORLD_ORES = new ConfiguredFeature<?, ?>[] {AMETHYST_ORE_OVERWORLD, LEAD_ORE_OVERWORLD}; NETHER_ORES = new ConfiguredFeature<?, ?>[] {AMETHYST_ORE_NETHER, LEAD_ORE_NETHER}; END_ORES = new ConfiguredFeature<?, ?>[] {AMETHYST_ORE_END, LEAD_ORE_END}; } OreFeatureAdditionManager.java /** * Apply {@value #overworldOres()}, {@value #netherOres} and {@value #endOres} to {@link Biome}s * of their various {@link Biome.Category}. * * @param event */ @SubscribeEvent(priority = EventPriority.HIGH) //Subbed to FORGE public static void registerOres(final BiomeLoadingEvent event) { MagiksMostEvile.LOGGER.debug("Adding MME ores to biome: " + event.getName()); BiomeGenerationSettingsBuilder generation = event.getGeneration(); switch (event.getCategory()) { case NETHER: for (ConfiguredFeature<?, ?> simpleConfiguredOreFeature : OreFeatures.NETHER_ORES) { registerTo(generation, simpleConfiguredOreFeature); } break; case THEEND: for (ConfiguredFeature<?, ?> simpleConfiguredOreFeature : OreFeatures.END_ORES) { registerTo(generation, simpleConfiguredOreFeature); } break; default: for (ConfiguredFeature<?, ?> simpleConfiguredOreFeature : OreFeatures.OVERWORLD_ORES) { registerTo(generation, simpleConfiguredOreFeature); } break; } } /** * Convenience method to tidy up {@link #registerOres(BiomeLoadingEvent)} by abstracting away * {@link BiomeGenerationSettingsBuilder} calls. * * @param builder * @param feature */ private static void registerTo(BiomeGenerationSettingsBuilder builder, ConfiguredFeature<?, ?> feature) { builder.withFeature(GenerationStage.Decoration.UNDERGROUND_ORES, feature); }

I haven't tried this but given that there are no other responses, I would start in a few places: ForgeRegistries.DIMENSIONS provides registration for dimensions through DeferredRegister. Search for the classes World and DimensionType - how does vanilla do it? Code to change dimension (i.e. through a portal) is: /** * Convenience method to change the dimension of the given entity. * * @param entityIn * @param worldIn */ private void changeDimension(Entity entityIn, World worldIn, RegistryKey<World> registryKey) { // Get the world of that key ServerWorld serverworld = ((ServerWorld) worldIn).getServer().getWorld(registryKey); // Change if (serverworld == null) { return; } entityIn.changeDimension(serverworld, new NoPortalTeleporter(serverworld)); } ... so World is evidently important. I'd also look into that RegistryKey business. Afraid I don't have a lot of other advice

I've made some additions - what stages should everything be occurring at? If I should use BiomeLoadingEvent to add features to a biome, which event should I be using to make and register the features themselves? Is there a way to do this with DeferredRegister?

The currently supported versions are 1.15 (LTS) and 1.16, as in the banner at the top of the page. Older versions are no longer supported.

Thanks @Beethoven92: I tried only using @Mod.EventBusSubscriber(modid = MagiksMostEvile.MODID, bus = Bus.FORGE), and combining the two methods into one call: /** * Called on {@link Bus.Forge}. Trigger ore registration. * * @param event */ @SubscribeEvent(priority = EventPriority.HIGH) public static void addOresToBiomes(final BiomeLoadingEvent event) { MagiksMostEvile.LOGGER.debug("Adding MME ores: Biome=" + event.getName()); createOreLists(); registerOres(event); } /** * Form the lists of ores to register * * @param event */ public static void createOreLists() { MagiksMostEvile.LOGGER.debug("Creating ore lists for MME feature addition!"); overworldOres(); netherOres(); endOres(); } (Result: Auto-subscribing genelectrovise.magiksmostevile.common.world.gen.ore.OreFeatureRegistry to FORGE) Two things: 1) This doesn't seem like the right way to handle this, though? Registering the features should not be done every time a biome is loaded - that seems wrong to me. 2) Whenever I try to join a world with that code active, I get this very odd error: [12:11:46] [Server thread/DEBUG] [ne.mi.fm.ne.FMLHandshakeHandler/FMLHANDSHAKE]: Handshake complete! [12:11:46] [Netty Local Client IO #0/INFO] [ne.mi.fm.ne.NetworkHooks/]: Connected to a modded server. [12:11:46] [Server thread/INFO] [ne.mi.co.AdvancementLoadFix/]: Using new advancement loading for net.minecraft.advancements.PlayerAdvancements@55ab5742 [12:11:46] [Server thread/INFO] [minecraft/PlayerList]: Dev[local:E:26a17569] logged in with entity id 257 at (-20.12474734205128, 72.0, 90.2353098908319) [12:11:46] [Server thread/INFO] [minecraft/MinecraftServer]: Dev joined the game [12:11:46] [Server thread/INFO] [minecraft/ServerPlayNetHandler]: Dev lost connection: Internal Exception: java.lang.ClassCastException: net.minecraft.network.login.ServerLoginNetHandler cannot be cast to net.minecraft.client.network.play.IClientPlayNetHandler [12:11:46] [Server thread/INFO] [minecraft/MinecraftServer]: Dev left the game [12:11:46] [Server thread/INFO] [minecraft/ServerPlayNetHandler]: Stopping singleplayer server as player logged out [12:11:46] [Server thread/INFO] [minecraft/MinecraftServer]: Stopping server Could this be a result of (1)? Maybe some strange de-sync issue?

What do you mean "don't work"? Does the server crash? Or does it run fine, but without mods? Please post logs!

Which version

I am adding natural Amethyst Ore generation to the world. I am receiving the loading error: [ne.mi.fm.ja.FMLModContainer/LOADING]: Failed to register automatic subscribers. ModID: magiksmostevile, class genelectrovise.magiksmostevile.common.core.MagiksMostEvile java.lang.IllegalArgumentException: Method public static void genelectrovise.magiksmostevile.common.world.gen.ore.OreFeatureRegistry.addOresToBiomes(net.minecraftforge.event.world.BiomeLoadingEvent) has @SubscribeEvent annotation, but takes an argument that is not a subtype of the base type interface net.minecraftforge.fml.event.lifecycle.IModBusEvent: class net.minecraftforge.event.world.BiomeLoadingEvent ... which is fairly obvious from looking through the heirarchy. All of these posts say to use BiomeLoadingEvent to register features: https://forums.minecraftforge.net/topic/92868-1163-biomeloadingevent/ https://forums.minecraftforge.net/topic/94945-1164how-to-generate-ores/ https://forums.minecraftforge.net/topic/90560-1162-how-to-add-custom-ore-to-world-generation/ https://forums.minecraftforge.net/topic/91702-1163-add-custom-generation/ ... but FML doesn't like me doing this. Should I be using another Event? Am I using this one correcly? My subscribed methods: /** * Form the lists of ores to register * * @param event */ @SubscribeEvent public static void createOreLists(final FMLCommonSetupEvent event) { overworldOres(); netherOres(); endOres(); } /** * Trigger ore registration. * * @param event */ @SubscribeEvent(priority = EventPriority.HIGH) public static void addOresToBiomes(final BiomeLoadingEvent event) { registerOres(event); } private static void overworldOres() { overworldOres .add(new SimpleConfiguredOreFeature.Builder().withSimpleOreFeature(new SimpleOreFeature()) .withSimpleOreFeatureConfiguration( new SimpleOreFeatureConfiguration(Blocks.STONE.getDefaultState(), EvileDeferredRegistry.AMETHYST_ORE_OVERWORLD.get().getDefaultState(), 10, true)) .build()); } Where I subscribe them: public MagiksMostEvile() { LOGGER.info("Magiks Most Evile is being loaded by FML"); EVENT_BUS = FMLJavaModLoadingContext.get().getModEventBus(); registerCommonEvents(); EvileDeferredRegistry.init(FMLJavaModLoadingContext.get().getModEventBus()); } public static void registerCommonEvents() { LOGGER.debug("Registering MME common events"); EVENT_BUS.register(OreFeatureRegistry.class); } The active branch of my GitHub repository: https://github.com/GenElectrovise/MagiksMostEvile/tree/feature/1.16.4/update_to_1.16.4/src/main/java/genelectrovise/magiksmostevile/common/world/gen Thanks!

Problem solved: I thought that the dependencies section of mods.toml was optional, though it seems that I did actually need this: [[dependencies.magiksmostevile]] #optional modId="forge" mandatory=true versionRange="[31,)" #mandatory # An ordering relationship for the dependency - BEFORE or AFTER required if the relationship is not mandatory ordering="NONE" # Side this dependency is applied on - BOTH, CLIENT or SERVER side="BOTH" # Here's another dependency [[dependencies.magiksmostevile]] modId="minecraft" mandatory=true versionRange="[1.16.4]" ordering="NONE" side="BOTH" Loads fine now - might have been something to do with some aspect FML being loaded after Magiks Most Evile? Don't especially know, but this is the solution. Now... Onwards and upwards to updating entities!

Hello! I'm updating my 1.15.2 mod (https://github.com/GenElectrovise/MagiksMostEvile/tree/1.15.2) to 1.16.4 (https://github.com/GenElectrovise/MagiksMostEvile/tree/1.16.4). I am receiving the error "The Mods File MagiksMostEvile/bin/main has mods that were not found". I suspect that it is an error with my mods.toml file, build.gradle, or my main Mod class though I cannot see the issue. The active development branch for this issue is https://github.com/GenElectrovise/MagiksMostEvile/tree/feature/1.16.4/update_to_1.16.4. I attach the latest log file with the error. Many thanks. latest.log

ArrowItem, ArrowEntity and BowItem will be a lot of help here. I believe there is also a Projectile class? (Also look at ShootableItem, I think it's called) That would be a good place to start -- when you boil it down, all you want to do is: 1) Make an item... 2) Which spawns a new entity when you right click... 3) Which then travels until it hits something... 4) And if it hits an Entity, damage it. Of course there's more you'd want to do, such as making it arc, charging up the bow, consuming ammo, etc..., but those are the basic steps. If you're familiar with onItemRightClick and making entities, you're already most of the way to something functional

Forge 1.16.1 32.0.7 just dropped and that *does* use vertical biome detection (visible in the nether from the vanilla F3 screen). Doubt many people know much about this right now... Time to investigate...

They want to craft a spawner block with a certain entity in it, which is something I have little experience of, so I gave the only bit of experience I had with dealing with spawner block tile entities.It isn't ideal, but I figured that the example would have at least some value with diesieben's suggestions.

Here is my base spawn egg class, which will set a Monster Spawner to the entity of the spawn egg. I don't know on the subject otherwise, but I hope the Monster-Spawner-Setting code will help... https://github.com/GenElectrovise/MagiksMostEvile/blob/1.15.2/src/main/java/genelectrovise/magiksmostevile/common/item/spawn_egg/EvileSpawnEgg.java#L79 (You'll be most interested in the stuff from line 89)

What version are you using? For 1.15.2: A crafting recipe for a spawn egg? Or a spawner block with a mob in it? If it's a custom item, make a normal crafting recipe for it. If it's a Minecraft spawn egg (from MC's SpawnEggItem) to spawn a custom entity, the Minecraft spawn egg system is not good for modding. You're better off making a custom item to spawn the entity, then following my last suggestion.

What exactly is your issue? Some code example would help