boop

NPC.java

package net.braehmc.bgnpc.NPC;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.mojang.authlib.GameProfile;
import com.mojang.authlib.properties.Property;
import net.minecraft.server.v1_8_R3.*;
import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.OfflinePlayer;
import org.bukkit.craftbukkit.v1_8_R3.CraftServer;
import org.bukkit.craftbukkit.v1_8_R3.CraftWorld;
import org.bukkit.craftbukkit.v1_8_R3.entity.CraftPlayer;
import org.bukkit.entity.Player;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.util.Collection;
import java.util.UUID;

public class NPC {
    private static void setNPCSkin(Player player, GameProfile gameProfile, String skinHolder) {
        try {
            lookUpNPCSkin(player, gameProfile, skinHolder);
        } catch (IOException exception) {
            exception.printStackTrace();
        }
    }

    @SuppressWarnings("deprecation")
    private static void lookUpNPCSkin(Player player, GameProfile gameProfile, String skinHolder) throws IOException {
        OfflinePlayer offlinePlayer = Bukkit.getOfflinePlayer(skinHolder);
        if (!offlinePlayer.isOnline()) {
            player.sendMessage(ChatColor.RED + "Could not retrieve skin metadata for " + ChatColor.DARK_AQUA + skinHolder + ChatColor.RED + "." + ChatColor.RESET);
            return;
        }
        String offlinePlayerUUID = offlinePlayer.getUniqueId().toString();
        String offlinePlayerTrimmedUUID = offlinePlayerUUID.replaceAll("-", "");
        String sessionServerInstance = "https://sessionserver.mojang.com/session/minecraft/profile/" + offlinePlayerTrimmedUUID + "?unsigned=false";

        URL sessionServer = new URL(sessionServerInstance);
        URLConnection sessionServerConnection = sessionServer.openConnection();
        InputStream sessionServerContent = sessionServerConnection.getInputStream();
        InputStreamReader sessionServerContentReader = new InputStreamReader(sessionServerContent);

        BufferedReader bufferedReader = new BufferedReader(sessionServerContentReader);
        String rawJsonContent = bufferedReader.readLine();

        JsonParser jsonParser = new JsonParser();
        JsonObject mainJsonObject = (JsonObject) jsonParser.parse(rawJsonContent);
        JsonArray propertiesArray = mainJsonObject.getAsJsonArray("properties");

        JsonObject mainJsonsPropertiesSubObject = (JsonObject) jsonParser.parse(propertiesArray.get(0).toString());
        JsonElement texture = mainJsonsPropertiesSubObject.get("value"); // Player's skin, named under "value"
        JsonElement signature = mainJsonsPropertiesSubObject.get("signature"); // Skin's signature

        gameProfile.getProperties().put("textures", new Property("textures", texture.getAsString(), signature.getAsString()));
    }

    public static void createNPC(Player player, String name, String skinHolder, int x, int y, int z, float yaw, float pitch) {
        MinecraftServer netMinecraftServer = ((CraftServer) Bukkit.getServer()).getServer();
        WorldServer netMinecraftServerWorld = ((CraftWorld) Bukkit.getWorlds().get(0)).getHandle();
        PlayerInteractManager playerInteractManager = new PlayerInteractManager(netMinecraftServerWorld);
        GameProfile gameProfile = new GameProfile(UUID.randomUUID(), name);
        setNPCSkin(player, gameProfile, skinHolder);
        EntityPlayer npc = new EntityPlayer(netMinecraftServer, netMinecraftServerWorld, gameProfile, playerInteractManager);
        npc.setLocation(x, y, z, yaw, pitch);

        DataWatcher dataWatcher = npc.getDataWatcher();
        dataWatcher.watch(10, (byte) 127);

        PacketPlayOutPlayerInfo packet1 = new PacketPlayOutPlayerInfo(PacketPlayOutPlayerInfo.EnumPlayerInfoAction.ADD_PLAYER, npc);
        PacketPlayOutNamedEntitySpawn packet2 = new PacketPlayOutNamedEntitySpawn(npc);
        PacketPlayOutEntityMetadata packet3 = new PacketPlayOutEntityMetadata(npc.getId(), dataWatcher, true);

        Collection<? extends Player> onlinePlayers = Bukkit.getOnlinePlayers();
        onlinePlayers.forEach(onlinePlayer -> {
            PlayerConnection playerConnection = ((CraftPlayer) onlinePlayer).getHandle().playerConnection;
            playerConnection.sendPacket(packet1);
            playerConnection.sendPacket(packet2);
            playerConnection.sendPacket(packet3);
        });
    }
}

Reminder to fix the NullPointerException caused by the OfflinePlayer Object

Fixed.