Solved How to spawn an Entity without triggering an EntitySpawnEvent

Hey!
So I'm writing a plugin, where every spawned mob gets replaced with a random mob (/Entity).
The Problem is after I removed the originally spawned Entity and spawned a new Entity, the Entity spawn event gets called again ( and again and again...). I can't figure out how to prevent that. Maybe someone can help me!

Here is my Code for the Listener:

Code:

    @EventHandler
    public void onMobSpawn(EntitySpawnEvent e) {
        if (arst == 1) {
// you can ignore that, just a simple check if the mobs should get replaced at all (activated through commands)
        Entity ent = e.getEntity();
        Location loc = ent.getLocation();
        if (ent.getType() == EntityType.EXPERIENCE_ORB) {
            return;
        }
// here are following even more entities that should not trigger the replace
        ent.remove();
        EntityType entrnd = null;
        while (entrnd == null) {
            entrnd = EntityType.values()[rnd.nextInt((EntityType.values()).length)];
            if (entrnd == EntityType.ENDER_DRAGON) {
                entrnd = null;
            }
//here are following even more Entities that shouldn't be the replacement
        }
        ent.getWorld().spawnEntity(loc, entrnd);
        entrnd = null;
        }

Thanks in advance!

 

You could have something like

Code:

List<UUID> spawnedEntities = new ArrayList<>();

@EventHandler
public void onMobSpawn(EntitySpawnEvent e) {
    UUID id = event.getEntity().getUniqueId();
    if(spawnedEntities.contains(id)){
        spawnedEntities.remove(id);
        return;
    }
    ....Your stuff...
   spawnedEntities.add(ent.getWorld().spawnEntity(loc, entrnd).getUniqueId());
}

 

I added your idea, but it still not worked :c

Here is my Code, did I do something wrong?

Code:

@EventHandler
    public void onMobSpawn(EntitySpawnEvent e) {
        if (arst == 1) {
//You can ignore that.
        Entity ent = e.getEntity();
        Location loc = ent.getLocation();
        if (ent.getType() == EntityType.EXPERIENCE_ORB) {
            return;
        }
//many more entities following, that should not be replaced
        ent.remove();
        EntityType entrnd = null;
        while (entrnd == null) {
            entrnd = EntityType.values()[rnd.nextInt((EntityType.values()).length)];
            if (entrnd == EntityType.ENDER_DRAGON) {
                entrnd = null;
            }
// and more entities that shouldn't be used for replacing following
        }
        spawnedEntities.add(ent.getWorld().spawnEntity(loc, entrnd).getUniqueId());
        entrnd = null;
        }
    }

Edit: It's still creates a loop

 

@FilBuild I belive you can add a boolean outside of your event to prevent this.

Code:Java

private boolean spawn = true;
 
@EventHandler
public void onMobSpawn(EntitySpawnEvent event) {
    if (!spawn) {
        spawn = true;
        return;
    }
    spawn = false;
 
    // Your code here
}

I believe this should work because Minecraft is single-threaded.

 

T̵r̵u̵e̵,̵ ̵b̵u̵t̵ ̵m̵u̵l̵t̵i̵p̵l̵e̵ ̵E̵n̵t̵i̵t̵y̵S̵p̵a̵w̵n̵E̵v̵e̵n̵t̵ ̵c̵a̵n̵ ̵b̵e̵ ̵t̵r̵i̵g̵g̵e̵r̵e̵d̵ ̵p̵e̵r̵ ̵t̵i̵c̵k̵.̵
̵M̵e̵a̵n̵i̵n̵g̵ ̵t̵h̵i̵s̵ ̵d̵o̵e̵s̵n̵'̵t̵ ̵g̵u̵a̵r̵a̵n̵t̵e̵e̵ ̵t̵h̵e̵ ̵v̵e̵r̵y̵ ̵n̵e̵x̵t̵ ̵t̵r̵i̵g̵g̵e̵r̵ ̵i̵s̵ ̵t̵h̵e̵ ̵e̵n̵t̵i̵t̵y̵ ̵j̵u̵s̵t̵ ̵s̵p̵a̵w̵n̵e̵d̵

 

You're calling the event using World#spawnEntity(...), which means that it'll run next.

 

#̵T̵i̵c̵k̵ ̵1̵ ̵>̵
̵-̵-̵>̵ ̵S̵p̵a̵w̵n̵e̵d̵ ̵C̵r̵e̵e̵p̵e̵r̵ ̵-̵>̵ ̵S̵p̵a̵w̵n̵ ̵e̵n̵t̵i̵t̵y̵ ̵&̵ ̵s̵e̵t̵ ̵b̵o̵o̵l̵e̵a̵n̵ ̵t̵o̵ ̵f̵a̵l̵s̵e̵;̵
̵-̵-̵>̵ ̵S̵p̵a̵w̵n̵e̵d̵ ̵Z̵o̵m̵b̵i̵e̵ ̵-̵>̵ ̵b̵o̵o̵l̵e̵a̵n̵ ̵i̵s̵ ̵f̵a̵l̵s̵e̵,̵ ̵s̵e̵t̵ ̵b̵o̵o̵l̵e̵a̵n̵ ̵t̵r̵u̵e̵ ̵d̵o̵ ̵n̵o̵t̵h̵i̵n̵g̵ ̵e̵l̵s̵e̵.̵
̵#̵T̵i̵c̵k̵ ̵2̵>̵
̵-̵-̵>̵ ̵S̵p̵a̵w̵n̵e̵d̵ ̵E̵n̵t̵i̵t̵y̵ ̵(̵f̵r̵o̵m̵ ̵t̵h̵e̵ ̵f̵i̵r̵s̵t̵ ̵c̵r̵e̵e̵p̵e̵r̵ ̵e̵v̵e̵n̵t̵)̵ ̵-̵>̵ ̵r̵e̵p̵l̵a̵c̵e̵ ̵t̵h̵i̵s̵ ̵e̵n̵t̵i̵t̵y̵ ̵t̵o̵o̵ ̵b̵e̵c̵a̵u̵s̵e̵ ̵b̵o̵o̵l̵e̵a̵n̵ ̵i̵s̵ ̵t̵r̵u̵e̵;̵

̵E̵v̵e̵n̵ ̵i̵f̵ ̵t̵h̵e̵ ̵n̵e̵w̵ ̵e̵n̵t̵i̵t̵y̵ ̵w̵a̵s̵ ̵s̵p̵a̵w̵n̵e̵d̵ ̵i̵n̵ ̵t̵h̵e̵ ̵s̵a̵m̵e̵ ̵t̵i̵c̵k̵ ̵(̵w̵h̵i̵c̵h̵ ̵I̵ ̵d̵o̵n̵'̵t̵ ̵t̵h̵i̵n̵k̵ ̵i̵t̵ ̵i̵s̵)̵,̵ ̵i̵t̵ ̵w̵o̵u̵l̵d̵ ̵s̵t̵i̵l̵l̵ ̵b̵e̵ ̵q̵u̵e̵u̵e̵d̵ ̵a̵f̵t̵e̵r̵ ̵t̵h̵e̵ ̵Z̵o̵m̵b̵i̵e̵,̵ ̵w̵h̵e̵r̵e̵ ̵'̵s̵p̵a̵w̵n̵'̵ ̵w̵o̵u̵l̵d̵ ̵b̵e̵ ̵t̵r̵u̵e̵ ̵a̵g̵a̵i̵n̵.̵

I'm wrong

̵A̵n̵d̵ ̵w̵e̵'̵r̵e̵ ̵g̵e̵t̵t̵i̵n̵g̵ ̵o̵f̵f̵ ̵t̵o̵p̵i̵c̵.̵
It didn't work @FilBuild b̵e̵c̵a̵u̵s̵e̵ ̵y̵o̵u̵ ̵m̵i̵s̵s̵e̵d̵ ̵t̵h̵e̵ ̵i̵f̵ ̵s̵t̵a̵t̵e̵m̵e̵n̵t̵ ̵i̵n̵ ̵m̵y̵ ̵f̵i̵r̵s̵t̵ ̵e̵x̵a̵m̵p̵l̵e̵

 

The "Spawned Entity" in your example would be spawned before the "Spawned Creeper", not in the next tick.
This has nothing to do with the Bukkit API, this is just how it works with a single thread.

Not quite; we're talking about the problem @FilBuild is having.

No, the World#spawnEntity(...) method calls the new EntitySpawnEvent before adding the entity to the list, which is causing the infinite loop.

 

That would make sense! But how can I prevent that?

I didn't missed it, I just forgot to paste it in here, my error. It still didn't work :c

Code:

@EventHandler
    public void onMobSpawn(EntitySpawnEvent e) {
        if (arst == 1) {
//You can ignore that.
        Entity ent = e.getEntity();
        Location loc = ent.getLocation();
        if (ent.getType() == EntityType.EXPERIENCE_ORB) {
            return;
        }

//many more entities following, that should not be replaced

         UUID id = e.getEntity().getUniqueId();
            if(spawnedEntities.contains(id)){
                spawnedEntities.remove(id);
                return;
            }

        ent.remove();
        EntityType entrnd = null;
        while (entrnd == null) {
            entrnd = EntityType.values()[rnd.nextInt((EntityType.values()).length)];
            if (entrnd == EntityType.ENDER_DRAGON) {
                entrnd = null;
            }
// and more entities that shouldn't be used for replacing following
        }
        spawnedEntities.add(ent.getWorld().spawnEntity(loc, entrnd).getUniqueId());
        entrnd = null;
        }
    }

And just for it to be complete ( in the case i did another paste error) here is the full code:

Full Code (open) Full Code (close)

Code:

package me.filip.rm.cmd;


import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.UUID;

import org.bukkit.Bukkit;
import org.bukkit.Location;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Entity;
import org.bukkit.entity.EntityType;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.EntitySpawnEvent;

import me.filip.rm.Main;
import me.filip.rm.utils.Utils;

public class Rmobs implements CommandExecutor, Listener{
    static int arst = 0;
    List<UUID> spawnedEntities = new ArrayList<>(); 
    static String chck = "rnd";
    Random rnd = new Random();
    @SuppressWarnings("unused")
    private Main plugin;
    public Rmobs(Main plugin) {
        this.plugin = plugin;
        plugin.getCommand("startrm").setExecutor(this);
        Bukkit.getPluginManager().registerEvents(this, plugin);
}
    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String string, String[] args) {
        if (arst == 1) {
            Bukkit.broadcastMessage(Utils.chat("&4Random Mobs has already started!"));
            return false;
        }
        arst = 1;
        Bukkit.broadcastMessage(Utils.chat("&3Random Mobs got started by " + sender.getName()));
        return false;
    }
    @EventHandler
    public void onMobSpawn(EntitySpawnEvent e) {
        if (arst == 1) {
        Entity ent = e.getEntity();
        Location loc = ent.getLocation();
        if (ent.getType() == EntityType.EXPERIENCE_ORB) {
            return;
        }
        if (ent.getType() == EntityType.DROPPED_ITEM) {
            return;
        }
        if (ent.getType() == EntityType.PLAYER) {
            return;
        }
        if (ent.getType() == EntityType.SPLASH_POTION) {
            return;
        }
        if (ent.getType() == EntityType.UNKNOWN) {
            return;
        }
        if (ent.getType() == EntityType.ARROW) {
            return;
        }
        if (ent.getType() == EntityType.COMPLEX_PART) {
            return;
        }
        if (ent.getType() == EntityType.FALLING_BLOCK) {
            return;
        }
        if (ent.getType() == EntityType.MINECART) {
            return;
        }
        if (ent.getType() == EntityType.MINECART_CHEST) {
            return;
        }
        if (ent.getType() == EntityType.THROWN_EXP_BOTTLE) {
            return;
        }
        if (ent.getType() == EntityType.FISHING_HOOK) {
            return;
        }
        if (ent.getType() == EntityType.LEASH_HITCH) {
            return;
        }
        if (ent.getType() == EntityType.BOAT) {
            return;
        }
        if (ent.getType() == EntityType.PAINTING) {
            return;
        }
        if (ent.getType() == EntityType.WITHER_SKULL) {
            return;
        }
        if (ent.getType() == EntityType.ENDER_DRAGON) {
            return;
        }
        if (ent.getType() == EntityType.WITHER) {
            return;
        }
        if (ent.getType() == EntityType.SILVERFISH) {
            return;
        }
        if (ent.getType() == EntityType.WEATHER) {
            return;
        }
         UUID id = e.getEntity().getUniqueId();
            if(spawnedEntities.contains(id)){
                spawnedEntities.remove(id);
                return;
            }
        ent.remove();
        EntityType entrnd = null;
        while (entrnd == null) {
            entrnd = EntityType.values()[rnd.nextInt((EntityType.values()).length)];
            if (entrnd == EntityType.ENDER_DRAGON) {
                entrnd = null;
            }
            if (entrnd == EntityType.COMPLEX_PART) {
                entrnd = null;
            }
            if (entrnd == EntityType.ENDER_PEARL) {
                entrnd = null;
            }
            if (entrnd == EntityType.FISHING_HOOK) {
                entrnd = null;
            }
            if (entrnd == EntityType.FALLING_BLOCK) {
                entrnd = null;
            }
            if (entrnd == EntityType.ITEM_FRAME) {
                entrnd = null;
            }
            if (entrnd == EntityType.ENDER_SIGNAL) {
                entrnd = null;
            }
            if (entrnd == EntityType.LEASH_HITCH) {
                entrnd = null;
            }
            if (entrnd == EntityType.MINECART_COMMAND) {
                entrnd = null;
            }
            if (entrnd == EntityType.DROPPED_ITEM) {
                entrnd = null;
            }
            if (entrnd == EntityType.PLAYER) {
                entrnd = null;
            }
            if (entrnd == EntityType.UNKNOWN) {
                entrnd = null;
            }
            if (entrnd == EntityType.WITHER_SKULL) {
                entrnd = null;
            }
            if (entrnd == EntityType.WITHER) {
                entrnd = null;
            }
            if (entrnd == EntityType.SMALL_FIREBALL) {
                entrnd = null;
            }
            if (entrnd == EntityType.FIREBALL) {
                entrnd = null;
            }
            if (ent.getType() == EntityType.PAINTING) {
                entrnd = null;
            }
            if (ent.getType() == EntityType.WEATHER) {
                entrnd = null;
            }
            if (ent.getType() == EntityType.MINECART_MOB_SPAWNER) {
                entrnd = null;
            }
            if (ent.getType() == EntityType.SNOWBALL) {
                entrnd = null;
            }
            if (ent.getType() == EntityType.SPLASH_POTION) {
                entrnd = null;
            }
        }
        spawnedEntities.add(ent.getWorld().spawnEntity(loc, entrnd).getUniqueId());
        entrnd = null;
        }
    }
 
}

 

@BrittleMind is a moron

@FilBuild , @KarimAKL 's solution should work just fine.
I didn't realize World#spawnEntity(...) would end up being recursive, therefore Entity#
getUniqueId() would never return

 

I did some testing too, this works like ~75% of the time. Which for my fun plugin is enough, but it still would be great, if we could get it to 100%.

Just to throw some ideas in, maybe if you can give the entity some form of tag, before it's gets spawned and then just check in the first part for it? I tried this already, but I only found a way to "tag" the entity after it got spawned, which of course is to late, because than the spawnevent is already triggered.

Then i did something wrong, here is my code:

Code:

package me.filip.rm.cmd;


import java.util.Random;

import org.bukkit.Bukkit;
import org.bukkit.Location;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Entity;
import org.bukkit.entity.EntityType;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.EntitySpawnEvent;

import me.filip.rm.Main;
import me.filip.rm.utils.Utils;

public class Rmobs implements CommandExecutor, Listener{
    static int arst = 0;
    static boolean pls = false;
    static String chck = "rnd";
    Random rnd = new Random();
    @SuppressWarnings("unused")
    private Main plugin;
    public Rmobs(Main plugin) {
        this.plugin = plugin;
        plugin.getCommand("startrm").setExecutor(this);
        Bukkit.getPluginManager().registerEvents(this, plugin);
}
    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String string, String[] args) {
        if (arst == 1) {
            Bukkit.broadcastMessage(Utils.chat("&4Random Mobs has already started!"));
            return false;
        }
        arst = 1;
        Bukkit.broadcastMessage(Utils.chat("&3Random Mobs got started by " + sender.getName()));
        return false;
    }
    @EventHandler
    public void onMobSpawn(EntitySpawnEvent e) {
        if (arst == 1) {
        Entity ent = e.getEntity();
        Location loc = ent.getLocation();
        if (ent.getType() == EntityType.EXPERIENCE_ORB) {
            return;
        }
        if (ent.getType() == EntityType.DROPPED_ITEM) {
            return;
        }
        if (ent.getType() == EntityType.PLAYER) {
            return;
        }
        if (ent.getType() == EntityType.SPLASH_POTION) {
            return;
        }
        if (ent.getType() == EntityType.UNKNOWN) {
            return;
        }
        if (ent.getType() == EntityType.ARROW) {
            return;
        }
        if (ent.getType() == EntityType.COMPLEX_PART) {
            return;
        }
        if (ent.getType() == EntityType.FALLING_BLOCK) {
            return;
        }
        if (ent.getType() == EntityType.MINECART) {
            return;
        }
        if (ent.getType() == EntityType.MINECART_CHEST) {
            return;
        }
        if (ent.getType() == EntityType.THROWN_EXP_BOTTLE) {
            return;
        }
        if (ent.getType() == EntityType.FISHING_HOOK) {
            return;
        }
        if (ent.getType() == EntityType.LEASH_HITCH) {
            return;
        }
        if (ent.getType() == EntityType.BOAT) {
            return;
        }
        if (ent.getType() == EntityType.PAINTING) {
            return;
        }
        if (ent.getType() == EntityType.WITHER_SKULL) {
            return;
        }
        if (ent.getType() == EntityType.ENDER_DRAGON) {
            return;
        }
        if (ent.getType() == EntityType.WITHER) {
            return;
        }
        if (ent.getType() == EntityType.SILVERFISH) {
            return;
        }
        if (ent.getType() == EntityType.WEATHER) {
            return;
        }
        if (pls == true) {
            pls = false;
            return;
        }
        ent.remove();
        EntityType entrnd = null;
        while (entrnd == null) {
            entrnd = EntityType.values()[rnd.nextInt((EntityType.values()).length)];
            if (entrnd == EntityType.ENDER_DRAGON) {
                entrnd = null;
            }
            if (entrnd == EntityType.COMPLEX_PART) {
                entrnd = null;
            }
            if (entrnd == EntityType.ENDER_PEARL) {
                entrnd = null;
            }
            if (entrnd == EntityType.FISHING_HOOK) {
                entrnd = null;
            }
            if (entrnd == EntityType.FALLING_BLOCK) {
                entrnd = null;
            }
            if (entrnd == EntityType.ITEM_FRAME) {
                entrnd = null;
            }
            if (entrnd == EntityType.ENDER_SIGNAL) {
                entrnd = null;
            }
            if (entrnd == EntityType.LEASH_HITCH) {
                entrnd = null;
            }
            if (entrnd == EntityType.MINECART_COMMAND) {
                entrnd = null;
            }
            if (entrnd == EntityType.DROPPED_ITEM) {
                entrnd = null;
            }
            if (entrnd == EntityType.PLAYER) {
                entrnd = null;
            }
            if (entrnd == EntityType.UNKNOWN) {
                entrnd = null;
            }
            if (entrnd == EntityType.WITHER_SKULL) {
                entrnd = null;
            }
            if (entrnd == EntityType.WITHER) {
                entrnd = null;
            }
            if (entrnd == EntityType.SMALL_FIREBALL) {
                entrnd = null;
            }
            if (entrnd == EntityType.FIREBALL) {
                entrnd = null;
            }
            if (entrnd == EntityType.PAINTING) {
                entrnd = null;
            }
            if (entrnd == EntityType.WEATHER) {
                entrnd = null;
            }
            if (entrnd == EntityType.MINECART_MOB_SPAWNER) {
                entrnd = null;
            }
            if (entrnd == EntityType.SNOWBALL) {
                entrnd = null;
            }
            if (entrnd == EntityType.SPLASH_POTION) {
                entrnd = null;
            }
            if (entrnd == EntityType.EXPERIENCE_ORB) {
                entrnd = null;
            }
            if (entrnd == EntityType.DROPPED_ITEM) {
                entrnd = null;
            }
            if (entrnd == EntityType.PLAYER) {
                entrnd = null;
            }
            if (entrnd == EntityType.SPLASH_POTION) {
                entrnd = null;
            }
            if (entrnd == EntityType.UNKNOWN) {
                entrnd = null;
            }
            if (entrnd == EntityType.ARROW) {
                entrnd = null;
            }
            if (entrnd == EntityType.COMPLEX_PART) {
                entrnd = null;
            }
            if (entrnd == EntityType.FALLING_BLOCK) {
                entrnd = null;
            }
            if (entrnd == EntityType.MINECART) {
                entrnd = null;
            }
            if (entrnd == EntityType.MINECART_CHEST) {
                entrnd = null;
            }
            if (entrnd == EntityType.THROWN_EXP_BOTTLE) {
                entrnd = null;
            }
            if (entrnd == EntityType.FISHING_HOOK) {
                entrnd = null;
            }
            if (entrnd == EntityType.LEASH_HITCH) {
                entrnd = null;
            }
            if (entrnd == EntityType.BOAT) {
                entrnd = null;
            }
            if (entrnd == EntityType.PAINTING) {
                entrnd = null;
            }
            if (entrnd == EntityType.WITHER_SKULL) {
                entrnd = null;
            }
            if (entrnd == EntityType.ENDER_DRAGON) {
                entrnd = null;
            }
            if (entrnd == EntityType.WITHER) {
                entrnd = null;
            }
            if (entrnd == EntityType.SILVERFISH) {
                entrnd = null;
            }
            if (entrnd == EntityType.WEATHER) {
                entrnd = null;
            }
            if (entrnd == ent.getType()) {
                entrnd = null;
            }
        }
        pls = true;
        ent.getWorld().spawnEntity(loc, entrnd);
        entrnd = null;
        }
    }
   
}

 

What do you mean by that? What part of it is not working? What is happening instead?

I haven't worked with this in quite a while but, i think this is possible by creating an entity using NMS and then adding it to the world.

A few suggestions:
1. You might want to create a list of entity types you want to have replaced.
2. 'arst' seems to be used as a toggle, why is it an integer instead of a boolean?
3. 'arst' and 'pls' doesn't need to be static.
4. Setting 'entrnd' to null at the end of the event method is not needed, it'll be out of scope anyway.
5. You might also want to name your variables something clearer. You don't have to give them all short names.
6. Booleans can be compared using '!' instead of '==' so, for your 'pls' check, you can use "if (pls)" instead of "if (pls == true)", if you're checking for 'false', you can do "if (!pls)".
7. You can cancel the event instead of removing the entity. Removing the entity might actually not even work.

 

Thanks for your tips, it seems like it's working now! Thank you all, i will mark this thread as solved!