getInt() 的 Java 无效值

Question

我尝试为 bukkit 制作一个脚本。如果它杀死僵尸，它需要在 mysql table 中上升 1。怎么了？还是有其他方法？

错误：java.sql.SQLException：getInt() 的无效值 - 'CraftZombie'

        PreparedStatement kills = connection.prepareStatement("SELECT ? FROM `data` WHERE name=?");
        kills.setString(1,entity.toString());
        kills.setString(2,name);
        ResultSet result = kills.executeQuery();


        String entity_string = entity.toString();

        result.next();
        //int score = 1;
        //score = result.getInt(1);
        //Integer score2 = (Integer) result.getObject(entity_string);

        int SC = result.getInt(entity_string);



        PreparedStatement stat = connection.prepareStatement("UPDATE data SET ?=? WHERE name=?",
                ResultSet.TYPE_FORWARD_ONLY,
                ResultSet.CONCUR_UPDATABLE);
        stat.setString(1,entity.toString());
        stat.setInt(2, SC + 1);
        stat.setString(3,name);

Answer 1

首先，不要在活动中做mysql查询，那样会导致服务器卡顿。

您必须使用要 link 到 mysql 服务器的数据创建 hashmap，并执行执行查询的调度程序异步任务。

示例：

package test;

import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Map.Entry;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;

import org.bukkit.entity.Player;
import org.bukkit.entity.Zombie;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.EntityDeathEvent;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scheduler.BukkitRunnable;

import com.mysql.jdbc.Connection;

public class Event extends JavaPlugin implements Listener {

    // Mysql update data
    public static ConcurrentHashMap<UUID, Integer> player_zombiekills = new ConcurrentHashMap<UUID, Integer>();

    // Mysql connection data
    public static Connection connection;
    private String host = "localhost";
    private String database = "DB";
    private String username = "user";
    private String password = "123";
    private int port = 3306;

    //Kill zombie event
    @EventHandler
    public void zombieDeath(EntityDeathEvent eve) {
        if (!(eve.getEntity() instanceof Zombie)) return; // Stop if death is not zombie
        if (!(eve.getEntity().getKiller() instanceof Player)) return; // Stop if killer is not player
        UUID uid = eve.getEntity().getKiller().getUniqueId(); // Save player uuid
        if (player_zombiekills.contains(uid)) player_zombiekills.put(uid, 0); // Set kills 0 if not exist in hashmap
        player_zombiekills.put(uid, player_zombiekills.get(uid) + 1); // plus 1 kills value
    }

    //On enable connection
    public void onEnable() {
        try {
            if (connection != null && !connection.isClosed()) return;
            Class.forName("com.mysql.jdbc.Driver");
            connection = (Connection) DriverManager.getConnection("jdbc:mysql://" + host + ":" + port + "/" + database, username, password);
            if (!connection.isClosed()) System.out.println("[MySQL] " + "Connected to '" + database + "'");
        } catch (Exception e) {
            System.err.println("[MySQL] " + e.getMessage());
        }

        new BukkitRunnable() {
            public void run() {
                // for updates
                for (Entry<UUID, Integer> ent : player_zombiekills.entrySet()) {
                    try {
                        // send update
                        connection.createStatement().executeUpdate("UPDATE `tablename` SET `zombiekills`=`zombiekills`+" + ent.getValue() + " WHERE `uuid`='" + ent.getKey().toString() + "'");
                        // Sucess remove entry from hashmap to reset kills
                        player_zombiekills.remove(ent.getKey());
                    } catch (SQLException e) { // If error
                        System.err.println("[MySQL] " + e.getMessage()); // Print error in console
                    }
                }
            }
        }.runTaskTimerAsynchronously(this, 20, 20 * 60 * 10); // Run async loop every 10 minutes
    }
}

getInt() 的 Java 无效值

JavaInvalid value for getInt()

java

mysql

minecraft

bukkit