A class that utilizes packets to use the boss health bar

BossBar

/**
 * BossBar
 * <br>
 * Create and save a new instance of this class and then use the setStatus method
 * to set the player's boss bar status
 * 
 * @author minnymin3
 * @license Lesser GNU Public License v3 (http://www.gnu.org/licenses/lgpl.html)
 * 
 */

public class BossBar {
	
	private Map<String, Dragon> dragonMap = new HashMap<String, Dragon>();

  /**
   * Sets the player's BossBar status
   * @param player The player to set status of
   * @param text The name of the boss bar
   * @param percent A value from 0-100 for the bar
   * @param reset Whether or not to create a new instance of the dragon (used when world changed)
   */
	public void setStatus(Player player, String text, int percent, boolean reset) {
		Dragon dragon = null;

		if (dragonMap.containsKey(player.getName()) && !reset) {
			dragon = dragonMap.get(player.getName());
		} else {
			dragon = new Dragon(text, player.getLocation().add(0, -200, 0), percent);
			Object mobPacket = dragon.getSpawnPacket();
			sendPacket(player, mobPacket);
			dragonMap.put(player.getName(), dragon);
		}

		if (text == "") {
			Object destroyPacket = dragon.getDestroyPacket();
			sendPacket(player, destroyPacket);
			dragonMap.remove(player.getName());
		} else {
			dragon.setName(text);
			dragon.setHealth(percent);
			Object metaPacket = dragon.getMetaPacket(dragon.getWatcher());
			Object teleportPacket = dragon.getTeleportPacket(player.getLocation().add(0, -200, 0));
			sendPacket(player, metaPacket);
			sendPacket(player, teleportPacket);
		}
	}
	
	private void sendPacket(Player player, Object packet) {
		try {
			Object nmsPlayer = getHandle(player);
			Field con_field = nmsPlayer.getClass().getField("playerConnection");
			Object con = con_field.get(nmsPlayer);
			Method packet_method = ReflectionUtils.getMethod(con.getClass(), "sendPacket");
			packet_method.invoke(con, packet);
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			e.printStackTrace();
		}
	}
	
	private Object getHandle(Entity entity) {
		Object nms_entity = null;
		Method entity_getHandle = ReflectionUtils.getMethod(entity.getClass(), "getHandle");
		try {
			nms_entity = entity_getHandle.invoke(entity);
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		}
		return nms_entity;
	}
	
	private class Dragon {

		private static final int MAX_HEALTH = 200;
		private int id;
		private int x;
		private int y;
		private int z;
		private int pitch = 0;
		private int yaw = 0;
		private byte xvel = 0;
		private byte yvel = 0;
		private byte zvel = 0;
		private float health;
		private boolean visible = false;
		private String name;
		private World world;

		private EntityEnderDragon dragon;

		public Dragon(String name, Location loc, int percent) {
			this.name = name;
			this.x = loc.getBlockX();
			this.y = loc.getBlockY();
			this.z = loc.getBlockZ();
			this.health = percent / 100F * MAX_HEALTH;
			this.world = ((CraftWorld) loc.getWorld()).getHandle();
		}

		public void setHealth(int percent) {
			this.health = percent / 100F * MAX_HEALTH;
		}

		public void setName(String name) {
			this.name = name;
		}

		public Object getSpawnPacket() {
			dragon = new EntityEnderDragon(world);
			dragon.setLocation(x, y, z, pitch, yaw);
			dragon.setInvisible(visible);
			dragon.setCustomName(name);
			dragon.setHealth(health);
			dragon.motX = xvel;
			dragon.motY = yvel;
			dragon.motZ = zvel;
			this.id = dragon.getId();
			PacketPlayOutSpawnEntityLiving packet = new PacketPlayOutSpawnEntityLiving(dragon);
			return packet;
		}

		public Object getDestroyPacket() {
			return new PacketPlayOutEntityDestroy(id);
		}

		public Object getMetaPacket(Object watcher) {
			return new PacketPlayOutEntityMetadata(this.id, (DataWatcher) watcher, true);
		}

		public Object getTeleportPacket(Location loc) {
			return new PacketPlayOutEntityTeleport(this.id, loc.getBlockX() * 32, loc.getBlockY() * 32, loc.getBlockZ() * 32,
					(byte) ((int)loc.getYaw() * 256 / 360), (byte) ((int)loc.getPitch() * 256 / 360));
		}

		public Object getWatcher() {
			DataWatcher watcher = new DataWatcher(dragon);
			watcher.a(0, visible ? (byte) 0 : (byte) 0x20);
			watcher.a(6, (Float) health);
			watcher.a(7, (Integer) 0);
			watcher.a(8, (Byte) (byte) 0);
			watcher.a(10, name);
			watcher.a(11, (Byte) (byte) 1);
			return watcher;
		}
		
	}
	
}