java连接MySql数据库

        咱们废话不多说,直接进入正题吧,要想连接数据库,首先得下载一个驱动,下面是下载链接

链接:https://pan.baidu.com/s/1gRj8n9sCP-aDQsJjHyCAow 
提取码:z9rj 

         要下载其他版本的驱动可以去官网下载  https://dev.mysql.com/downloads/connector/j/

         驱动下载之后呢,在想要使用数据库的项目的下方新建一个lib目录,把驱动复制到这个目录下面

如下图所示:

         

然后鼠标右键点击此项目,选择buildpath-->configure build path-->libraries-->Add JRs..,然后选择lib目录下的驱动,点击确定就OK啦,这个时候Referenced Libraries里面就有刚才的驱动啦

        准备工作做好之后呢,就可以写程序啦,代码如下:

  

import java.sql.*;
public class Test {
//JDBC驱动名称及数据库URL
	static final String JDBC_DRIVER="com.mysql.jdbc.Driver";
	static final String DB_URL="jdbc:mysql://localhost:3306/student";
	//数据库的用户名与密码
	static final String USER="root";
	static final String PASS="ly1314520";
	public static void main(String args[]){
		Connection conn=null;
		Statement stmt=null;
		try{
			Class.forName("com.mysql.jdbc.Driver");//注册JDBC驱动
			//打开连接
			System.out.println("连接数据库。。。");
			conn=DriverManager.getConnection(DB_URL,USER,PASS);
			System.out.println("实例化Statement对象....");
			stmt=conn.createStatement();
			String sql;
			sql="SELECT id,name,url FROM website";
			ResultSet rs=stmt.executeQuery(sql);
			//展开结果集数据库
			while(rs.next()){
				int id=rs.getInt("id");
				String name =rs.getString("name");
				String url=rs.getString("url");
				//输出数据
				System.out.print("ID: "+id);
				System.out.print(",站点名称:"+name);
				System.out.print(",站点URL: "+url);
				System.out.print("\n");
			}
			rs.close();
			stmt.close();
			conn.close();
		}catch(SQLException se){
			se.printStackTrace();//处理错误
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			//关闭资源
			try{
				if(stmt!=null) stmt.close();
			}catch(SQLException se2){
				
			}
			try{
				if(conn!=null) conn.close();
			}catch(SQLException se){
				se.printStackTrace();
			}
		}
		System.out.println("Good Bye");
	}
}

好啦,这次就到这里啦

通过 systemctl status caddy.service 获取服务状态和关键错误提示,root@kb751gzo:~# systemctl status caddy.service × caddy.service - Caddy Loaded: loaded (/lib/systemd/system/caddy.service; enabled; vendor preset: enabled) Active: failed (Result: exit-code) since Sun 2025-03-09 03:25:34 CST; 3min 17s ago Docs: https://caddyserver.com/docs/ Process: 194947 ExecStart=/usr/bin/caddy run --environ --config /etc/caddy/Caddyfile (code=exited, status=1/FAILURE) Main PID: 194947 (code=exited, status=1/FAILURE) Status: "loading new config: http app module: start: listening on :80: listen tcp :80: bind: address already in use" CPU: 96ms Mar 09 03:25:34 kb751gzo.vm caddy[194947]: {"level":"info","ts":1741461934.6543036,"msg":"adapted config to JSON","adapter":"caddyfile"} Mar 09 03:25:34 kb751gzo.vm caddy[194947]: {"level":"warn","ts":1741461934.6543362,"msg":"Caddyfile input is not formatted; run 'caddy fmt --overwrite'> Mar 09 03:25:34 kb751gzo.vm caddy[194947]: {"level":"info","ts":1741461934.65588,"logger":"admin","msg":"admin endpoint started","address":"localhost:2> Mar 09 03:25:34 kb751gzo.vm caddy[194947]: {"level":"warn","ts":1741461934.656203,"logger":"http.auto_https","msg":"server is listening only on the HTT> Mar 09 03:25:34 kb751gzo.vm caddy[194947]: {"level":"info","ts":1741461934.6562505,"logger":"http.auto_https","msg":"enabling automatic HTTP->HTTPS red> Mar 09 03:25:34 kb751gzo.vm caddy[194947]: {"level":"info","ts":1741461934.6562598,"logger":"tls.cache.maintenance","msg":"started background certifica> Mar 09 03:25:34 kb751gzo.vm caddy[194947]: Error: loading initial config: loading new config: http app module: start: listening on :80: listen tcp :80:> Mar 09 03:25:34 kb751gzo.vm systemd[1]: caddy.service: Main process exited, code=exited, status=1/FAILURE Mar 09 03:25:34 kb751gzo.vm systemd[1]: caddy.service: Failed with result 'exit-code'. Mar 09 03:25:34 kb751gzo.vm systemd[1]: Failed to start Caddy.
03-10
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