Make attributes work in creative mode.

AttributesExample.java

package com.comphenix.example;

import java.io.DataInputStream;
import java.io.IOException;
import java.util.List;

import org.bukkit.Material;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.Listener;
import org.bukkit.event.inventory.InventoryCreativeEvent;
import org.bukkit.inventory.ItemStack;
import org.bukkit.plugin.java.JavaPlugin;

import com.comphenix.example.Attributes.Attribute;
import com.comphenix.example.Attributes.AttributeType;
import com.comphenix.protocol.Packets;
import com.comphenix.protocol.ProtocolLibrary;
import com.comphenix.protocol.events.ConnectionSide;
import com.comphenix.protocol.events.ListenerOptions;
import com.comphenix.protocol.events.PacketAdapter;
import com.comphenix.protocol.events.PacketEvent;
import com.comphenix.protocol.utility.MinecraftReflection;
import com.comphenix.protocol.utility.StreamSerializer;
import com.comphenix.protocol.wrappers.nbt.NbtCompound;
import com.comphenix.protocol.wrappers.nbt.NbtFactory;

public class AttributesExample extends JavaPlugin implements Listener {
    private ItemStack expectedCursor;
    private long expectedTime;
    
    @Override
    public void onEnable() {
        getServer().getPluginManager().registerEvents(this, this);
        
        ProtocolLibrary.getProtocolManager().addPacketListener(
            new PacketAdapter(
                    this, ConnectionSide.CLIENT_SIDE, new ListenerOptions[] { ListenerOptions.INTERCEPT_INPUT_BUFFER }, Packets.Client.SET_CREATIVE_SLOT) {
            @Override
            public void onPacketReceiving(PacketEvent event) {
                DataInputStream input = event.getNetworkMarker().getInputStream();
                try {
                    // Read slot
                    input.readShort();
                    ItemStack stack = readItemStack(input, new StreamSerializer());

                    // Undo the stupid "item meta" cleanup
                    event.getPacket().getItemModifier().write(0, stack);
                    
                    // Update the next event handler
                    expectedTime = System.currentTimeMillis();
                    expectedCursor = stack;
                    
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }
    
    @EventHandler(priority = EventPriority.LOWEST)
    public void onCreativeInventory(InventoryCreativeEvent e) {
        if ((System.currentTimeMillis() - expectedTime) < 50) {
            e.setCursor(expectedCursor);
        }
    }   
    
    private ItemStack readItemStack(DataInputStream input, StreamSerializer serializer) throws IOException {
        ItemStack result = null;
        short type = input.readShort();

        if (type >= 0) {
            byte amount = input.readByte();
            short damage = input.readShort();

            result = new ItemStack(type, amount, damage);
            NbtCompound tag = serializer.deserializeCompound(input);

            if (tag != null) {
                result = MinecraftReflection.getBukkitItemStack(result);
                NbtFactory.setItemTag(result, tag);
            }
        }
        return result;
    }
    
    @Override
    public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
        if (sender instanceof Player) {
            ItemStack helmet = new ItemStack(Material.GOLD_HELMET);
            Attributes attributes = new Attributes(helmet);

            attributes.add(Attribute.newBuilder().name("Health")
                    .type(AttributeType.GENERIC_MAX_HEALTH).amount(20).build());

            attributes.add(Attribute.newBuilder().name("Speed")
                    .type(AttributeType.GENERIC_MOVEMENT_SPEED).amount(2).build());

            ((Player) sender).getInventory().addItem(attributes.getStack());
        }
        return true;
    }
}