java - 插入 MySQL Java

Question

我的 mysql setBanned 语句有问题。我试图将一个用户设置为禁止进入数据库，但它向我抛出“连接关闭后不允许进行任何操作”。谁能帮帮我？

它抛出一个错误

statement.setString(3, reason);

在setBanned代码中。

当前的 setBanned 代码:

    public boolean setBanned(Player player, boolean state, String reason){
    Connection conn = null;
    PreparedStatement statement = null;
    String setBanned = "INSERT INTO `test_bans` (UUID, BANNED, REASON) VALUES ( ?, ?, ?)";
    String setUnbanned = "UPDATE `test_bans` SET BANNED= ? WHERE UUID= ?";
    try{
        conn = MySql.getConnection();
        if(isBanned(player) && state == false){
            statement = conn.prepareStatement(setUnbanned);
            statement.setBoolean(1, state);
            statement.setString(2, player.getUniqueId().toString());
            statement.executeUpdate();
        } else {
            statement = conn.prepareStatement(setBanned);
            statement.setString(1, player.getUniqueId().toString());
            statement.setBoolean(2, state);
            statement.setString(3, reason);
            statement.executeUpdate();
        }
    } catch (SQLException e){
        e.printStackTrace();
    } finally {
        if(statement != null){
            try{
                statement.close();
            } catch (SQLException e){
                e.printStackTrace();
            }
        }
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e){
                e.printStackTrace();
            }
        }
    }
    return false;
}

被禁止的代码:

    public boolean isBanned(Player player){
    Connection conn = null;
    PreparedStatement statement = null;
    ResultSet result = null;
    String query = "SELECT BANNED FROM `test_bans` WHERE UUID= ?";
    try{
        conn = MySql.getConnection();
        statement = conn.prepareStatement(query);
        statement.setString(1, player.getUniqueId().toString());
        result = statement.executeQuery();
        return result.next();
    } catch (SQLException e){
        e.printStackTrace();
    } finally {
        if (result != null){
            try{
                result.close();
            } catch (SQLException e){
                e.printStackTrace();
            }
        }
        if(statement != null){
            try{
                statement.close();
            } catch (SQLException e){
                e.printStackTrace();
            }
        }
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e){
                e.printStackTrace();
            }
        }
    }
    return false;
}

编辑:MySQL 类

public class MySql {

private static String DATABASE_NAME ="testing_database";
private static String DATABASE_IP   ="localhost:3306";
private static String connection    ="jdbc:mysql://"+DATABASE_IP+"/"+DATABASE_NAME;
private static String username      ="root";
private static String password      ="pass";

private static Connection conn;

public static void handleConnection(){
    Bukkit.getServer().getLogger().info("Establishing connection to MySQL Database....");
    try{
        conn = DriverManager.getConnection(connection, username, password);
        if(!conn.isClosed()){
            Bukkit.getServer().getLogger().info("Successfully synced with MySQL!");
            return;
        }
        return;
    }
    catch (SQLException e){
        e.printStackTrace();
        return;
    }
}

public static void disconnectConnection(){
    Bukkit.getServer().getLogger().info("Disconnecting from MySQL Databse....");
    try{
        conn.close();
        if(conn.isClosed()){
            Bukkit.getServer().getLogger().info("Successfully Disconnected");
        }
        return;
    }
    catch(SQLException e){
        e.printStackTrace();
        return;
    }
}

public static boolean setupTables(){
    try{
        System.out.println("Checking Tables");
        conn.prepareStatement("CREATE TABLE IF NOT EXISTS test_ranks (UUID VARCHAR(255), RANK VARCHAR(25));").executeUpdate();
        conn.prepareStatement("CREATE TABLE IF NOT EXISTS test_bans (UUID VARCHAR(255), BANNED BOOLEAN, REASON TEXT);").executeUpdate();
        return true;
    }
    catch(SQLException e){
        e.printStackTrace();
        return false;
    }
}

public static boolean checkConnection(){
    try{
        if((conn != null) && (!conn.isClosed())){
            return true;
        }
        return false;
    }
    catch(SQLException e){
        e.printStackTrace();
        return false;
    }
}

public static Connection getConnection(){
    try {
        if(conn.isClosed()){
            connectMySQL();
            return conn;
        }
        if(conn == null){
            connectMySQL();
            return conn;
        }
    } catch (SQLException e){
        e.printStackTrace();
    }
    return conn;
}

public static void connectMySQL(){
    try {
        conn = DriverManager.getConnection(connection, username, password);
        return;
    } catch(SQLException e){
        e.printStackTrace();
    }
}

Answer 1

你的问题不清楚....

没有任何类 MySql。如果它的自定义类...提供它的代码片段。

Mysql JDBC连接的实际使用方式

Class.forName("com.mysql.jdbc.Driver");
Connection conn = null;
conn = DriverManager.getConnection("jdbc:mysql://hostname:port/dbname","username", "password");

//Create statement

//Execute statement
//Iterate over results  
//close statement  
conn.close(); // close connection