Riding projectiles in Minecraft.

mockup.java

    /**
     * 
     *  Do note: only Arrow and ThrownExpBottle work with this method.
     *           The rest was just testing material.
     * 
     **/
    
    
    Team team;

    @CommandHandler(name = "testcommand")
    public boolean test(CommandSender sender, String label, String[] args)
    {
        if(sender instanceof Player)
        {
            Player player = (Player) sender;
            Scoreboard sb = player.getScoreboard();
            team = sb.registerNewTeam(player.getName());
            team.addPlayer(player);
            team.setAllowFriendlyFire(false);
            Class<? extends Projectile> clazz = Arrow.class;
            if(args.length > 0)
                if(args[0].equalsIgnoreCase("ep"))
                    clazz = EnderPearl.class;
                else if(args[0].equalsIgnoreCase("sb"))
                    clazz = Snowball.class;
                else if(args[0].equalsIgnoreCase("egg"))
                    clazz = Egg.class;
                else if(args[0].equalsIgnoreCase("exp"))
                    clazz = ThrownExpBottle.class;

            Projectile arrow = player.launchProjectile(clazz);
            if(clazz == EnderPearl.class || clazz == Snowball.class || clazz == Egg.class)
            {
                Projectile ws = player.getWorld().spawn(player.getLocation(), WitherSkull.class);
                arrow.setPassenger(ws);
                arrow = ws;
            }
            arrow.setPassenger(player);
        }
        return true;
    }

    @EventHandler
    public void on(ProjectileHitEvent event)
    {
        ProjectileSource source = event.getEntity().getShooter();
        if(source instanceof Player)
        {
            team.removePlayer((Player)source);
            team.unregister();
            Entity passenger = event.getEntity().getPassenger();
            event.getEntity().remove();
            if(passenger instanceof WitherSkull)
            {
                passenger.eject();
                passenger.remove();
            }
            event.getEntity().remove();
        }
    }