Bugs with simple plugin

Hi, my friend had make plugin, and here's the code - but monsters don't attack players and mobs are dissaperaing when noone is nearly - can onyone help ? It's a plugin that disable monsters & mobs from spawn, and allow spawn them by command.

Code:

package bukkit.Nsuidara.Spawner;
import org.bukkit.event.Event;
import org.bukkit.event.Event.Priority;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.plugin.PluginManager;

public class Spawner extends JavaPlugin
{
@Override
public void onDisable()
{

}

public ListnerPlayer vPListner = new ListnerPlayer(this);
public ListnerMobs vMListner = new ListnerMobs(this);
public boolean vOFF = true;

public void onEnable()
{
 System.out.println("Start Pluginu");
 PluginManager gManager = getServer().getPluginManager();
 gManager.registerEvent(Event.Type.CREATURE_SPAWN, vMListner, Priority.Highest, this);
 gManager.registerEvent(Event.Type.PLAYER_COMMAND_PREPROCESS , vPListner, Priority.Highest, this);
}a
}
16:49:14
package bukkit.Nsuidara.Spawner;

import org.bukkit.Location;
import org.bukkit.World;
import org.bukkit.entity.CreatureType;
import org.bukkit.entity.Player;
import org.bukkit.event.player.PlayerCommandPreprocessEvent;
import org.bukkit.event.player.PlayerListener;

public class ListnerPlayer extends PlayerListener
{
private Spawner vPlugin = null;
public ListnerPlayer(Spawner _Plugin)
{
 vPlugin = _Plugin;
}

public void onPlayerCommandPreprocess(PlayerCommandPreprocessEvent _Event)
{
 if(_Event.getMessage().contains(" "))
 {
  String[] _Split = _Event.getMessage().split(" ");
  Player _Player = _Event.getPlayer();
  World _World = _Player.getLocation().getWorld();

  if(_Split[0].equalsIgnoreCase("/monster") && _Player.isOp())
     {
   CreatureType vType = null;
   if(_Split[1].equalsIgnoreCase("CHICKEN"))
    vType = CreatureType.CHICKEN;
   else if(_Split[1].equalsIgnoreCase("COW"))
    vType = CreatureType.COW;
   else if(_Split[1].equalsIgnoreCase("CREEPER"))
    vType = CreatureType.CREEPER;
   else if(_Split[1].equalsIgnoreCase("GHAST"))
    vType = CreatureType.GHAST;
   else if(_Split[1].equalsIgnoreCase("GIANT"))
    vType = CreatureType.GIANT;
   else if(_Split[1].equalsIgnoreCase("MONSTER"))
    vType = CreatureType.MONSTER;
   else if(_Split[1].equalsIgnoreCase("PIG"))
    vType = CreatureType.PIG;
   else if(_Split[1].equalsIgnoreCase("PIG_ZOMBIE"))
    vType = CreatureType.PIG_ZOMBIE;
   else if(_Split[1].equalsIgnoreCase("SHEEP"))
    vType = CreatureType.SHEEP;
   else if(_Split[1].equalsIgnoreCase("SKELETON"))
    vType = CreatureType.SKELETON;
   else if(_Split[1].equalsIgnoreCase("SLIME"))
    vType = CreatureType.SLIME;
   else if(_Split[1].equalsIgnoreCase("SPIDER"))
    vType = CreatureType.SPIDER;
   else if(_Split[1].equalsIgnoreCase("SQUID"))
    vType = CreatureType.SQUID;
   else if(_Split[1].equalsIgnoreCase("WOLF"))
    vType = CreatureType.WOLF;
   else if(_Split[1].equalsIgnoreCase("ZOMBIE"))
    vType = CreatureType.ZOMBIE;
   else
   {
    _Player.sendMessage("Zwierze/Potwor o takiej nazwie nie istnieje!");
    _Event.setCancelled(true);
    return;
   }

   if(_Split.length == 4)
   {
    int oMax = Integer.parseInt(_Split[2]);
    int oR = Integer.parseInt(_Split[3]);

    for(int i = 0; i < oMax; i++)
    {
     Location oLocation = _Player.getLocation();
     double oX = oLocation.getX()+Math.random()*(2*oR) - oR;
     double oZ = oLocation.getZ()+Math.random()*(2*oR) - oR;
     oLocation.setX(oX);
     oLocation.setZ(oZ);
     vPlugin.vOFF = false;
     _World.spawnCreature(oLocation, vType);

    }
    _Player.sendMessage("Summoned!! "+vType.getName()+"x"+oMax+" R = "+oR);
   }
   else if(_Split.length == 3)
   {
    int oMax = Integer.parseInt(_Split[2]);
    for(int i = 0; i < oMax; i++)
    {
     vPlugin.vOFF = false;
     _World.spawnCreature(_Player.getLocation(), vType);
    }
   }
   else if(_Split.length == 2)
   {
    _World.spawnCreature(_Player.getLocation(), vType);
   }
     }
 }
}
}
16:49:28
package bukkit.Nsuidara.Spawner;

import org.bukkit.event.entity.CreatureSpawnEvent;
import org.bukkit.event.entity.EntityDeathEvent;
import org.bukkit.event.entity.EntityListener;

public class ListnerMobs extends EntityListener
{
private Spawner vPlugin = null;
public ListnerMobs(Spawner _Plugin)
{
 vPlugin = _Plugin;
}

public void onCreatureSpawn(CreatureSpawnEvent event)
{
 if(vPlugin.vOFF == true)
  event.setCancelled(true);
 else
  vPlugin.vOFF = true;
}

}