http://www.bukkit.fr/topic/19059-r%C3%A9cup%C3%A9rer-le-poseur-dun-oeuf/

EntityOwnership.java

package fr.neatmonster.plugin;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.UUID;

import org.bukkit.Location;
import org.bukkit.Material;
import org.bukkit.entity.EntityType;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.CreatureSpawnEvent;
import org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason;
import org.bukkit.event.entity.EntityTargetEvent;
import org.bukkit.event.player.PlayerInteractEvent;

public class EntityOwnership implements Listener {
    private static final double        MAX_DISTANCE = 5;
    private final Map<UUID, Location>  history      = new HashMap<>();
    private final Map<UUID, Set<UUID>> relations    = new HashMap<>();

    @EventHandler(priority = EventPriority.MONITOR, ignoreCancelled = true)
    public void onPlayerInteract(final PlayerInteractEvent event) {
        if (event.hasBlock() && event.hasItem() && event.getItem().getType() == Material.MONSTER_EGG)
            history.put(event.getPlayer().getUniqueId(), event.getClickedBlock().getLocation());
    }

    @EventHandler(priority = EventPriority.MONITOR, ignoreCancelled = true)
    public void onCreatureSpawn(final CreatureSpawnEvent event) {
        final UUID ownee = event.getEntity().getUniqueId();
        if (event.getSpawnReason() == SpawnReason.SPAWNER_EGG) {
            final Location location = event.getLocation();

            UUID owner = null;
            double minDistance = Double.MAX_VALUE;
            for (final Entry<UUID, Location> entry : history.entrySet()) {
                final double distance = location.distance(entry.getValue());
                if (distance < minDistance && distance < MAX_DISTANCE) {
                    owner = entry.getKey();
                    minDistance = distance;
                }
            }

            if (owner != null) {
                if (!relations.containsKey(owner))
                    relations.put(owner, new HashSet<UUID>());
                relations.get(owner).add(ownee);
                history.remove(owner);
            }
        }
    }

    @EventHandler(ignoreCancelled = true)
    public void onEntityTarget(final EntityTargetEvent event) {
        final UUID ownee = event.getEntity().getUniqueId();
        if (event.getTarget().getType() == EntityType.PLAYER) {
            final UUID owner = event.getTarget().getUniqueId();

            if (relations.containsKey(owner)) {
                final Set<UUID> ownees = relations.get(owner);
                if (ownees.contains(ownee))
                    event.setCancelled(true);
            }
        }
    }
}