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[1.8]Generating Mob Spawners


JoieNL
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Hello fellow modders,

 

Lately I found myself at an impasse when trying to generate mob spawners in my custom structure. The generation of the spawner itself is not the problem, but rather the specifics of the spawner and the mob spawned. For the spawner itself, I want to be able to set the initial spawn delay, spawned mob, number of mobs spawned each time, spawn range, minimum and maximum delay between spawns, maximum nearby entities and required player distance to the spawner. For the spawned mob, I would like to add equipment (i.e. a weapon and armour) and maybe give it some potion effects. Now, I know how to do the latter if I have an instance of an EntityLiving, but I cannot figure out how to get said instance (and then set it) for a spawner. Please let me know if what I want is even possible with Minecraft's default classes, and, if it's not, how I would go about making custom spawner classes. Thanks in advance!

 

PS: Here is my code for reference:

Spoiler

public static void generateWaterTower(int x, int y, int z, Random random, World world) {
	BlockPos origin = new BlockPos(x, getTopBlock(new BlockPos(x, y, z), world).getY(), z);
	(...)
	world.setBlockState(origin.add(11, 1, 11), Blocks.mob_spawner.getDefaultState());
	TileEntityMobSpawner spawner = (TileEntityMobSpawner) world.getTileEntity(origin.add(11, 1, 11));
	(...)
}

 

 

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Quote

Why are you using 1.8?

I am using 1.8 mostly because I cannot stand the combat system introduced in 1.9. Either way, I do not plan to update.

 

Quote

The MobSpawnerBaseLogic of the spawner lets you modify what should be spawned.

Right, but it only allows you to pass a String (that is, the mobID), which means you can only set what kind of creature you want it to spawn, not the specifics of both the spawner and the spawned creature.

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17 minutes ago, JoieNL said:

I am using 1.8 mostly because I cannot stand the combat system introduced in 1.9. Either way, I do not plan to update.

At least use 1.8.9 then. And 1.8.x is not going to be supported much longer on this forum, just FYI.

 

MobSpawnerBaseLogic::getRandomEntity returns the WeightedRandomMinecart (that's what you get for using an outdated version, stupid names) instance, which stores the information about the entity to be spawned.

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14 minutes ago, diesieben07 said:

At least use 1.8.9 then. And 1.8.x is not going to be supported much longer on this forum, just FYI.

Well, I am using 1.8.9, I just figured the the topic pertained to the entirety of 1.8.

 

1 hour ago, diesieben07 said:

MobSpawnerBaseLogic::getRandomEntity returns the WeightedRandomMinecart (that's what you get for using an outdated version, stupid names) instance, which stores the information about the entity to be spawned.

So by configuring the NBT of this WeightedRandomMinecart instance I can apply armour and potion effects to the spawned entity? Alright, but then how about the properties of the spawner itself?

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I have figured out how to edit the mob spawner's characteristics through the use of reflection. Now, I have been trying to configure the spawned entity's characteristics by using reflection to edit the NBTTagCompound "nbtData" in the inner class WeightedRandomMinecart in MobSpawnerBaseLogic. After many fruitless attempts, I just don't know what to try anymore. How do I go about setting "nbtData" while using the right arguments in Field::set(Object obj, Object value) and how do I convert (an array of) ItemStacks to NBT that MobSpawnerBaseLogic can read?

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1 minute ago, diesieben07 said:

This does not make sense, the NBT is for an entity, not for ItemStacks.

Perhaps I should have been a bit more elaborate. The array of ItemStacks would be the equipment the Entity must have.

 

As for my current code...

MobSpawnerExtendedLogic.class:

Spoiler

public static void setNBT(Object object) {
    NBTTagList tagList = new NBTTagList();
    ItemStack[] equipment = new ItemStack[] {new ItemStack(ModItems.osmiumSword), new ItemStack(ModItems.osmiumBoots), new ItemStack(ModItems.osmiumLeggings), new ItemStack(ModItems.osmiumChestplate), new ItemStack(ModItems.osmiumHelmet)};
    for (ItemStack stack : equipment) {
        NBTTagCompound nbttagcompound = new NBTTagCompound();
        stack.writeToNBT(nbttagcompound);
        tagList.appendTag(nbttagcompound);
    }
    NBTTagCompound tag = new NBTTagCompound();
    tag.setTag("Equipment", tagList);
    NBTTagCompound tagCompound = new NBTTagCompound();
    tagCompound.setTag("Properties", tag);
    try {
        Field field = MobSpawnerBaseLogic.WeightedRandomMinecart.class.getDeclaredField("nbtData");
        field.setAccessible(true);
        Field modifiersField = Field.class.getDeclaredField("modifiers");
        modifiersField.setAccessible(true);
        modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
        Field randomEntity = MobSpawnerBaseLogic.class.getDeclaredField("randomEntity");
        randomEntity.setAccessible(true);
        Object obj = randomEntity.get(object);
        field.set(obj, tagCompound);
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }
}

 

 

WaterTower.class:

world.setBlockState(origin.add(11, 1, 11), Blocks.mob_spawner.getDefaultState());
TileEntityMobSpawner spawner = (TileEntityMobSpawner) world.getTileEntity(origin.add(11, 1, 11));
setNBT(spawner.getSpawnerBaseLogic());

 

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  • 2 weeks later...

Well, after a lot of trial and error, I've figured things out. I am now able to configure the specifics of a generated mob spawner, as well as the specifics of the entitiy it should spawn. All these values are contained within the MobSpawnerBaseLogic class. I created a class, MobSpawnerExtendedLogic, that extends that class in which I created methods for modifying all these values. The methods I created use Java's reflection system. The methods are static because I have to use them in a static context. The argument to pass in as spawnerLogic should be the logic of the spawner you are trying to modify. For a spawner positioned at BlockPos pos in World world, you would pass ((TileEntityMobSpawner) world.getTileEntity(pos))).getSpawnerBaseLogic(). Here are my MobSpawnerExtendedLogic class and an implementation of the methods within it:

 

MobSpawnerExtendedLogic.class:

Spoiler

public abstract class MobSpawnerExtendedLogic extends MobSpawnerBaseLogic {
    /**
     *
     * @param mobID The {@code String} that represents the Entity the spawner should spawn.
     * @param initialSpawnDelay The delay (in ticks) between when the player first enters the spawner's range and the first spawn.
     * @param minDelay The minimum delay between two spawns.
     * @param maxDelay The maximum delay between two spawns.
     * @param spawnCount The amount of Entities spawned every spawn.
     * @param spawnRange The range (cuboid with height 3 and remaining sides of range) in which spawned Entities should be placed.
     * @param maxNearbyEntities If this or a greater number of Entities is within the spawner's spawn range, it will stop spawning Entities.
     * @param minPlayerDistance The minimum distance between a player and the spawner at which the spawner should activate.
     * @param spawnerLogic A reference to the spawner's logic.
     */
    public static void setSpawnerSpecifics(String mobID, int initialSpawnDelay, int minDelay, int maxDelay, int spawnCount, int spawnRange, int maxNearbyEntities, int minPlayerDistance, MobSpawnerBaseLogic spawnerLogic) {
        setMobID(mobID, spawnerLogic);
        setInitialSpawnDelay(initialSpawnDelay, spawnerLogic);
        setMinDelay(minDelay, spawnerLogic);
        setMaxDelay(maxDelay, spawnerLogic);
        setSpawnCount(spawnCount, spawnerLogic);
        setSpawnRange(spawnRange, spawnerLogic);
        setMaxNearbyEntities(maxNearbyEntities, spawnerLogic);
        setMinPlayerDistance(minPlayerDistance, spawnerLogic);
    }

    /**
     *
     * @param entity The entity to spawn.
     * @param initialSpawnDelay The delay (in ticks) between when the player first enters the spawner's range and the first spawn.
     * @param minDelay The minimum delay between two spawns.
     * @param maxDelay The maximum delay between two spawns.
     * @param spawnCount The amount of Entities spawned every spawn.
     * @param spawnRange The range (cuboid with height 3 and remaining sides of range) in which spawned Entities should be placed.
     * @param maxNearbyEntities If this or a greater number of Entities is within the spawner's spawn range, it will stop spawning Entities.
     * @param minPlayerDistance The minimum distance between a player and the spawner at which the spawner should activate.
     * @param spawnerLogic A reference to the spawner's logic.
     */
    public static void setSpawnerSpecifics(EntityLiving entity, int initialSpawnDelay, int minDelay, int maxDelay, int spawnCount, int spawnRange, int maxNearbyEntities, int minPlayerDistance, MobSpawnerBaseLogic spawnerLogic) {
        NBTTagCompound compound = new NBTTagCompound();
        entity.writeEntityToNBT(compound);
        setNBT(entity.getName(), compound, spawnerLogic);
        setInitialSpawnDelay(initialSpawnDelay, spawnerLogic);
        setMinDelay(minDelay, spawnerLogic);
        setMaxDelay(maxDelay, spawnerLogic);
        setSpawnCount(spawnCount, spawnerLogic);
        setSpawnRange(spawnRange, spawnerLogic);
        setMaxNearbyEntities(maxNearbyEntities, spawnerLogic);
        setMinPlayerDistance(minPlayerDistance, spawnerLogic);
    }

    private static void setMobID(String id, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("mobID");
            field.setAccessible(true);
            field.set(obj, id);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    private static void setInitialSpawnDelay(int delay, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("spawnDelay");
            field.setAccessible(true);
            field.set(obj, delay);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    private static void setMinDelay(int delay, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("minSpawnDelay");
            field.setAccessible(true);
            field.set(obj, delay);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    private static void setMaxDelay(int delay, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("maxSpawnDelay");
            field.setAccessible(true);
            field.set(obj, delay);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    private static void setSpawnCount(int count, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("spawnCount");
            field.setAccessible(true);
            field.set(obj, count);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    private static void setSpawnRange(int range, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("spawnRange");
            field.setAccessible(true);
            field.set(obj, range);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    private static void setMaxNearbyEntities(int count, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("maxNearbyEntities");
            field.setAccessible(true);
            field.set(obj, count);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    private static void setMinPlayerDistance(int distance, MobSpawnerBaseLogic obj) {
        try {
            Field field = MobSpawnerBaseLogic.class.getDeclaredField("activatingRangeFromPlayer");
            field.setAccessible(true);
            field.set(obj, distance);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }

    @SuppressWarnings("JavaReflectionMemberAccess")
    private static void setNBT(String mobID, NBTTagCompound compound, MobSpawnerBaseLogic obj) {
        try {
            Constructor constructor = MobSpawnerBaseLogic.WeightedRandomMinecart.class.getDeclaredConstructor(MobSpawnerBaseLogic.class, NBTTagCompound.class, String.class);
            Field randomEntity = MobSpawnerBaseLogic.class.getDeclaredField("randomEntity");
            randomEntity.setAccessible(true);
            randomEntity.set(obj, constructor.newInstance(obj, compound, mobID));
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }
}

 

 

An implementation of the methods:

Spoiler

EntityZombie zombie1 = new EntityZombie(world);
applyRandomTierFourArmour(zombie1);
for (int i = 0; i < 5; i++) {
    zombie1.setEquipmentDropChance(i, 0);
}
zombie1.addPotionEffect(new PotionEffect(Potion.moveSpeed.getId(), 1000000, 0));
world.setBlockState(origin.add(6, 1, 6), Blocks.mob_spawner.getDefaultState());
setSpawnerSpecifics(zombie1, 0, 40, 100, 1, 16, 8, 16, ((TileEntityMobSpawner) world.getTileEntity(origin.add(6, 1, 6))).getSpawnerBaseLogic());

world.setBlockState(origin.add(11, 18, 11), Blocks.mob_spawner.getDefaultState());
setSpawnerSpecifics("em.ice_cube", 0, 100, 200, 3, 10, 8, 11, ((TileEntityMobSpawner) world.getTileEntity(origin.add(11, 18, 11))).getSpawnerBaseLogic());

 

 

Edited by JoieNL
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I think an important option you've failed to consider is you don't need to use the vanilla mob spawner, rather you can create your own custom ones that extend the vanilla one , and have those placed during structure generation, and have them do the initial logic you want (or otherwise expose the private fields through setter and getter methods), etc. I'm not exactly sure why you need to do the reflection part.  

Check out my tutorials here: http://jabelarminecraft.blogspot.com/

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