空指针异常 Java 我的世界 MySQL

Question

我现在正在开发 Minecraft / TeamSpeak³ 验证系统。但是当我想连接到我的数据库时，它给了我一个

java.lang.NullPointerException

。这是代码

public class MySQL {

    public String host = "localhost";
    public String database = "tsverify";
    public String username = "silentgames";
    public String password = "Epic_Password";
    public Connection con;

    public void connect() {
        if (!isConnected()) {
            try
            {
                con = DriverManager.getConnection("jdbc:mysql://" + host + ":3306/" + database + "?autoReconnect=true", username, password);
                System.out.println("[MySQL] [Sync] Verbindung aufgebaut!");
            }
            catch (SQLException e)
            {
                System.out.println("[MySQL] Connection failed");
                e.printStackTrace();
            }
        }
    }
}

我已经检查了登录数据，是的，它是正确的。另外，数据库名称是正确的。我还在onEnable()方法中加入了mysql.connect()方法，所以是真正连接数据库。请帮助我！

Answer 1

我建议按以下方式添加Class.forName("com.mysql.cj.jdbc.Driver")：

public class MySQL {

    public String host = "localhost";
    public String database = "tsverify";
    public String username = "silentgames";
    public String password = "Epic_Password";
    public Connection con;

    public void connect() {
        if (!isConnected()) {
            try
            {
                Class.forName("com.mysql.cj.jdbc.Driver");
                con = DriverManager.getConnection("jdbc:mysql://" + host + ":3306/" + database + "?autoReconnect=true", username, password);
                System.out.println("[MySQL] [Sync] Verbindung aufgebaut!");
            }
            catch (SQLException e)
            {
                System.out.println("[MySQL] Connection failed");
                e.printStackTrace();
            }
        }
    }

}

空指针异常 Java 我的世界 MySQL

NullPointer Excpetion Java Minecraft MySQL

java

mysql

database

minecraft