我的mysql 版本是 5.1.30

新建 MySqlUtil.java 文件

package com.JavaMySqlJdbc.dbMySql;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class MySqlUtil {
    //是否连接数据库
    public static String mysql_open="false";
    //数据库连接地址
    public static String mysql_url="jdbc:mysql://localhost:3306/callcenter2_db";
    //用户名
    public static String mysql_username= "root";
    //密码
    public static String mysql_password ="";//admindljjk
    //驱动名称
    public static String mysql_driver = "com.mysql.jdbc.Driver";
    private static Connection conn = null;
    public static Connection getConn() {
        try {
            Class.forName(mysql_driver);
            conn = DriverManager.getConnection(mysql_url, mysql_username, mysql_password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
            closeConn();
        return conn;
    public static void closeConn(){
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
App.java
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
import java.util.UUID;
import com.JavaMySqlJdbc.dbMySql.MySqlUtil;
public class App 
    public static void main( String[] args )
        System.out.println( "Hello World!-------JavaMySqlJbdc-------------" );
        MySqlUtil.mysql_url = "jdbc:mysql://localhost:3306/callcenter2_db_rencai?useUnicode=true&characterEncoding=utf-8&useSSL=false";
        MySqlUtil.mysql_username = "root";
        MySqlUtil.mysql_password = "";
        MySqlUtil.mysql_driver = "com.mysql.jdbc.Driver";
        System.out.println( "url:   " +MySqlUtil.mysql_url);
        //查询----------------------------------------------------------
        String strPassword=getPasswordByUserName("管理员8001");
        System.out.println( "密码:   " +strPassword);
        //新增--------------------------------------------------------------
        //SQL语句
        String strId = UUID.randomUUID().toString();//唯一码
        String event = "event 2323";
        String callid = "callid 132343298432";
        String surveyresult = "2";
        String sn = "3121231231.02131";
        String sql = "insert into ls_satisfaction ";
        sql = sql + " (id,event1,callid,surveyresult,sn ) ";
        sql = sql + " values ('"+strId+"','"+event+"','"+callid+"','"+surveyresult+"','"+sn+"' ) ";
        int intResult=ExecuteUpdate(sql);
        System.out.println( "执行结果:   " +intResult);
    private static int ExecuteUpdate(String sql) {
        Connection conn = MySqlUtil.getConn();
        Statement stmt = null;
        //ResultSet ret = null;
        int intResult = -1;
        try {
            stmt = conn.createStatement();
            //执行语句，得到结果集
            intResult = stmt.executeUpdate(sql);
            if(intResult>0)
                //影响一行以上
            }else{
                //没有影响一行
            conn.close();//关闭连接
        } catch (SQLException e1) {
            e1.printStackTrace();
        return intResult;
    //查询
    private static String getPasswordByUserName(String userName) {
        //SQL语句
        String sql = "select user_password from user where user_name = " + "'" + userName + "'";
        Connection conn = MySqlUtil.getConn();
        Statement stmt = null;
        ResultSet ret = null;
        String password = null;
        try {
            stmt = conn.createStatement();
            //执行语句，得到结果集
            ret = stmt.executeQuery(sql);
            while (ret.next()) {
                //这里只查询的密码
                password = ret.getString(1);
            ret.close();
            conn.close();//关闭连接
        } catch (SQLException e1) {
            e1.printStackTrace();
        return password;
    }
}
}
java.sql.SQLException: Unknown system variable 'language'
使用jdbc连接数据库提示以上错误，上网查了问题大部分都说是jdbc驱动和mysql版本不匹配，目前我mysql版本为5.1.30，
jdbc版本是5.1.40,将jdbc版本改为5.0.8,数据显示正确！！！！
小石潭记丶
https://blog.csdn.net/qq_33371766/article/details/80229166
weixin_37250058
https://blog.csdn.net/weixin_37250058/article/details/54019789