1.7.2 Update

BossBarManager.java

//Accessing packets
    private Object getMobPacket(){
        Location loc = entity.getLocation().subtract(0, 5, 0);

        Class<?> mob_class = ReflectionHelper.getNMSClass("PacketPlayOutSpawnEntityLiving");
        Object mobPacket = null;
        try {
            mobPacket = mob_class.newInstance();

            Field a = ReflectionHelper.getField(mob_class, "a");
            a.setAccessible(true);
            a.set(mobPacket, ENTITY_ID);//Entity ID
            Field b = ReflectionHelper.getField(mob_class, "b");
            b.setAccessible(true);
            b.set(mobPacket, (byte) EntityType.ENDER_DRAGON.getTypeId());//Mob type id
            Field c = ReflectionHelper.getField(mob_class, "c");
            c.setAccessible(true);
            c.set(mobPacket, loc.getBlockX());//X position
            Field d = ReflectionHelper.getField(mob_class, "d");
            d.setAccessible(true);
            d.set(mobPacket, loc.getBlockY());//Y position
            Field e = ReflectionHelper.getField(mob_class, "e");
            e.setAccessible(true);
            e.set(mobPacket, loc.getBlockZ());//Z position
            Field i = ReflectionHelper.getField(mob_class, "i");
            i.setAccessible(true);
            i.set(mobPacket, (byte) 0);//Yaw
            Field j = ReflectionHelper.getField(mob_class, "j");
            j.setAccessible(true);
            j.set(mobPacket, (byte) 0);//Pitch
            Field k = ReflectionHelper.getField(mob_class, "k");
            k.setAccessible(true);
            k.set(mobPacket, (byte) 0);//Head Pitch
            Field f = ReflectionHelper.getField(mob_class, "f");
            f.setAccessible(true);
            f.set(mobPacket, (byte) 0);//X velocity
            Field g = ReflectionHelper.getField(mob_class, "g");
            g.setAccessible(true);
            g.set(mobPacket, (byte) 0);//Y velocity
            Field h = ReflectionHelper.getField(mob_class, "h");
            h.setAccessible(true);
            h.set(mobPacket, (byte) 0);//Z velocity
            Field l = ReflectionHelper.getField(mob_class, "l");
            l.setAccessible(true);
            l.set(mobPacket, getWatcher());
        } catch (Throwable e1) {
            e1.printStackTrace();
        }

        return mobPacket;
    }

    private Object getDestroyEntityPacket(){
        Class<?> packet_class = ReflectionHelper.getNMSClass("PacketPlayOutEntityDestroy");
        Object packet = null;
        try {
            packet = packet_class.newInstance();

            Field a = ReflectionHelper.getField(packet_class, "a");
            a.setAccessible(true);
            a.set(packet, new int[]{ENTITY_ID});
        } catch (Throwable e) {
            e.printStackTrace();
        }

        return packet;
    }

    private Object getMetadataPacket(Object watcher){
        Class<?> packet_class = ReflectionHelper.getNMSClass("PacketPlayOutEntityMetadata");
        Object packet = null;
        try {
            packet = packet_class.newInstance();
            Method watcher_c = ReflectionHelper.getMethodNoArgs(watcher.getClass(), "c");

            Field a = ReflectionHelper.getField(packet_class, "a");
            a.setAccessible(true);
            a.set(packet, ENTITY_ID);
            Field b = ReflectionHelper.getField(packet_class, "b");
            b.setAccessible(true);
            b.set(packet, watcher_c.invoke(watcher));
        } catch (Throwable e) {
            e.printStackTrace();
        }

        return packet;
    }

    private Object getRespawnPacket(){
        Class<?> packet_class = ReflectionHelper.getNMSClass("PacketPlayOutRespawn");
        Object packet = null;
        try {
            packet = packet_class.newInstance();

            Field a = ReflectionHelper.getField(packet_class, "a");
            a.setAccessible(true);
            a.set(packet, 1);
        } catch (Throwable e) {
            e.printStackTrace();
        }

        return packet;
    }

    private Object getWatcher(){
        Class<?> watcher_class = ReflectionHelper.getNMSClass("DataWatcher");
        Object watcher = null;
        try {
            Constructor<?> constructor = watcher_class.getConstructor(net.minecraft.server.v1_7_R1.Entity.class);
            watcher = constructor.newInstance(new Object[]{ null });

            Method a = ReflectionHelper.getMethod(watcher_class, "a", new Class<?>[]{int.class, Object.class});
            a.setAccessible(true);
            a.invoke(watcher, 0, (byte) 0x20);
            a.invoke(watcher, 6, ((float) (entity.isDead() ? 1 : entity.getHealth())) / Math.round(entity.getMaxHealth()) * 200);
            a.invoke(watcher, 7, 0);
            a.invoke(watcher, 8, (byte) 0);
            a.invoke(watcher, 10, getDisplayName());
            a.invoke(watcher, 11, (byte) 1);
        } catch (Throwable e) {
            e.printStackTrace();
        }

        return watcher;
    }