错误 - 无法找到或加载主类 [英] Error - Could not find or load main class

问题描述

我想连接我的java程序来连接数据库并检索数据。
编译完美但运行时
我得到这个错误：无法找到或加载主类

I want to connect my java program to connect with database and retrieve the data. its compile perfectly but runtime im getting this Error : Could not find or load main class

我已经安装了Java SQL驱动程序并将环境变量的jar路径添加为CLASSPATH

i have installed the Java SQL driver and added the jar path to the Environmental variable as CLASSPATH

import java.sql.*;
public class Java2Sql{
    public static void main(String args[]){
        String url = "jdbc:mysql://localhost:80/";
        String dbName = "test";
        String driver = "com.mysql.jdbc.Driver";
        String userName = "root";
        String password = "root";

        try{
            Class.forName(driver).newInstance();
            Connection conn = DriverManager.getConnection(url+dbName,userName,password);

            Statement stmt = conn.createStatement();
            String strsql = "SELECT * FROM student";

            ResultSet res = stmt.executeQuery(strsql);

            while(res.next()){
                System.out.println("ID :"+res.getString(1));
                System.out.println("Name :"+res.getString(2));
                System.out.println("Tel :"+res.getString(3));
                System.out.println("City :"+res.getString(4));
            }
            res.close();
            conn.close();
        }catch(Exception e){
            e.printStackTrace();
        }

    }
}

推荐答案

您应该从这里下载驱动程序

和JAR文件需要添加到项目类路径。

and JAR file need to add to project class path.

首先右键单击Eclipse项目，项目 - - >构建路径 - >配置构建路径。在Libraries选项卡下，单击Add Jars或Add External JARs并添加下载的jar

First Right click on you Eclipse Project, Project --> Build Path --> Configure Build Path. Under Libraries tab, click Add Jars or "Add External JARs" and add downloaded jar

不是100％肯定，但看起来你使用的是错误的端口号80.确保你的MySQL端口号是当前的以下语句

Not 100% sure but looks like you are using wrong port number 80. Make sure your MySQL port number is current by below statement

SHOW VARIABLES WHERE Variable_name = 'port';

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