JDBC连接MySQL数据库，访问数据库信息完成登录功能——保姆级详细教程（附所有java和jsp源代码）

前言

众所周知，我们在使用JAVA开发的时候，用户的数据都是存放在数据库当中的，可是市面上有那么多种类的数据库，为了统一各个数据库和java的连接规范，就出现了JDBC。

JDBC的介绍

JDBC为访问不同数据库提供了统一的接口，java程序员使用JDBC，可以连接任何提供JDBC驱动程序的数据库系统，从而完成对数据库的各种操作。

通过JDBC连接MySQL数据库

导入mysql驱动

这个驱动其实就是一个规范接口，需要连接MySQL数据库就下载匹配本机mysql版本的对应驱动，然后导入即可。

连接数据库

连接数据库

String url ="jdbc:mysql://localhost:3306/abc";   //abc为数据库名称
String  user = "root";        //定义字符串变量存入mysql登录名
String password = "123456";     //定义字符串存入mysql登录密码
Class.forName("com.mysql.jdbc.Driver");  //加载mysql驱动          
Connection connection = DriverManager.getConnection(url,user,password);
Statement statement = connection.createStatement();   //建立连接

判断连接是否成功

if (conn!=null){
            out.print("连接成功"+"
");
}else{
            out.print("连接失败"+"
");
}

使用数据库实现登录

获取前端表单的用户输入

String s1=request.getParameter("username");
String s2=request.getParameter("password");
request.setAttribute("s1", s1);

判断用户名和密码为空

//判断用户名、密码是否为空
if(s1 == "" || s1.length() == 0){
	request.setAttribute("namemsg","用户名为空!");
	request.getRequestDispatcher("index.jsp").forward(request, response);
}
if(s2== "" || s2.length() == 0){
	request.setAttribute("pwdmsg","密码为空!");
	request.getRequestDispatcher("index.jsp").forward(request, response);
}

查询表

String sql = String.format("SELECT * FROM login WHERE `username` = '%s' AND `password` = '%s'",s1,s2);
            ResultSet resultSet = statement.executeQuery(sql);//返回的结果集

判断用户名和密码的匹配

if (resultSet.next()){
	request.getRequestDispatcher("login.jsp").forward(request,response); //匹配成功进入登录成功页面
}else if(s1.equals("") || s2.equals("")){
	request.getRequestDispatcher("loginf.jsp").forward(request,response);  //用户名和密码有一个村务
}else{
request.getRequestDispatcher("loginf.jsp").forward(request,response);  //用户和密码全部错误
}

实现整体代码(需要自提，记得点赞)

Servlet代码（loginServlet.java）

package servlet;

import java.io.IOException;
import java.sql.*;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * @author s
 * @version 1.0
 */
@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public loginServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String s1=request.getParameter("username");
        String s2=request.getParameter("password");
        request.setAttribute("s1", s1);

        //判断用户名、密码是否为空
        if(s1 == "" || s1.length() == 0){
            request.setAttribute("namemsg","用户名为空!");
            request.getRequestDispatcher("index.jsp").forward(request, response);
        }
        if(s2== "" || s2.length() == 0){
            request.setAttribute("pwdmsg","密码为空!");
            request.getRequestDispatcher("index.jsp").forward(request, response);
        }
        //密码部分结束
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");

        //加载mysql驱动
        String url ="jdbc:mysql://localhost:3306/abc";
        String  user = "root";
        String password = "123456";
        try {
            Class.forName("com.mysql.jdbc.Driver");
            // 连接数据库
            Connection connection = DriverManager.getConnection(url,user,password);
            Statement statement = connection.createStatement();
            String sql = String.format("SELECT * FROM login WHERE `username` = '%s' AND `password` = '%s'",s1,s2);
            ResultSet resultSet = statement.executeQuery(sql);//返回的结果集
            if (resultSet.next()){
                request.getRequestDispatcher("login.jsp").forward(request,response);
            }else if(s1.equals("") || s2.equals("")){
                request.getRequestDispatcher("loginf.jsp").forward(request,response);
            }
            else{request.getRequestDispatcher("loginf.jsp").forward(request,response);}
        }catch(ClassNotFoundException | SQLException e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }
}

jsp代码(index.jsp)

<%--
  Created by IntelliJ IDEA.
  User: 86151
  Date: 2022/5/24
  Time: 14:32
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
  String path = request.getContextPath();
  String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>




  
  
  
  
  
  
  
  
  



  

    

      

        
用户名:
        
 
          ${requestScope.namemsg}${requestScope.nameError}
      
      

        
密码:
        
 
          ${requestScope.pwdError}${requestScope.pwdmsg}
      
      

        

        

          

        
      
    
  

<%--
--%>
<%--  管理员登录--%>
<%--
--%>

实现效果

登录页面

账号 or 密码 为null

两个账户分别登录成功

登录失败