Adds an entity spawn listener for preventing Zombified Piglin spawns

src/main/java/net/knarcraft/stargate/Stargate.java

@@ -10,6 +10,7 @@ import net.knarcraft.stargate.container.BlockChangeRequest;
 import net.knarcraft.stargate.container.ChunkUnloadRequest;
 import net.knarcraft.stargate.listener.BlockEventListener;
 import net.knarcraft.stargate.listener.EntityEventListener;
+import net.knarcraft.stargate.listener.EntitySpawnListener;
 import net.knarcraft.stargate.listener.PlayerEventListener;
 import net.knarcraft.stargate.listener.PluginEventListener;
 import net.knarcraft.stargate.listener.PortalEventListener;
@@ -388,6 +389,7 @@ public class Stargate extends JavaPlugin {
         pluginManager.registerEvents(new WorldEventListener(), this);
         pluginManager.registerEvents(new PluginEventListener(this), this);
         pluginManager.registerEvents(new TeleportEventListener(), this);
+        pluginManager.registerEvents(new EntitySpawnListener(), this);
     }
 
     /**

src/main/java/net/knarcraft/stargate/listener/EntitySpawnListener.java

@@ -0,0 +1,25 @@
+package net.knarcraft.stargate.listener;
+
+import net.knarcraft.stargate.Stargate;
+import net.knarcraft.stargate.portal.PortalHandler;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.entity.CreatureSpawnEvent;
+
+/**
+ * A listener that listens for any relevant events causing entities to spawn
+ */
+public class EntitySpawnListener implements Listener {
+
+    @EventHandler
+    public void onCreatureSpawn(CreatureSpawnEvent event) {
+        //Prevent Zombified Piglins and other creatures form spawning at stargates
+        if (event.getSpawnReason() == CreatureSpawnEvent.SpawnReason.NETHER_PORTAL) {
+            if (PortalHandler.getByEntrance(event.getLocation()) != null) {
+                event.setCancelled(true);
+                Stargate.debug("EntitySpawnListener", "Prevented creature from spawning at Stargate");
+            }
+        }
+    }
+
+}