解决com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure, The last packe.

本文介绍: 希望这篇文章能帮助你解决“com.mysql.cj.jdbc.exception s.Co m munica t ion sExc ept ion: Co m munication s link fa ilure, The last pack et s ent success full y to th e server was 0 m illi s ec o nd s a go. The driver has not rec e i v e d any pack e ts from the server.”的错误，顺利连接到MySQL服务器。

解决com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure, The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

shellCopy codeping <mysql_server_ip_address&gt;

shellCopy codesudo service mysql status

shellCopy codesudo nano /etc/mysql/mysql.conf.d/mysqld.cnf

shellCopy codesudo service mysql restart

javaCopy codeString url = "jdbc:mysql://<mysql_server_ip_address&gt;:<port>/<database_name>";

javaCopy codeString user = "your_username";
String password = "your_password";

javaCopy codeimport java.sql.*;
public class MySQLConnectionExample {
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String DB_USER = "username";
    private static final String DB_PASSWORD = "password";
    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            // 1. 注册MySQL JDBC驱动程序
            Class.forName("com.mysql.cj.jdbc.Driver");
            // 2. 建立数据库连接
            connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
            // 3. 创建Statement对象，执行SQL查询
            statement = connection.createStatement();
            String sql = "SELECT * FROM mytable";
            resultSet = statement.executeQuery(sql);
            // 4. 处理查询结果
            while (resultSet.next()) {
                // 读取数据
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                int age = resultSet.getInt("age");
                System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age);
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 5. 释放资源
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (statement != null) {
                    statement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}