JavaWeb MySQL 实现登录验证

0.环境准备

项目创建：

IDEA 创建 Servlet 项目详细步骤:https://www.jianshu.com/p/386a79d16e05

导入 MySQL 驱动包：

Java MySQL 连接:https://eslsuwen.github.io/2019/06/02/Java-MySQL/

1.创建测试数据

接下来我们在 MySQL 中创建 usersdb 数据库，并创建 user 数据表，表结构如下：

CREATE TABLE `user` (
  `name` char(20) NOT NULL DEFAULT '' COMMENT 'name',
  `password` char(10) NOT NULL DEFAULT '' COMMENT 'password'
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;

插入一些数据：

INSERT INTO `user`
VALUES
	( 'admin', 'admin' ),
	( ' guest ', ' 123456 ' ),
	( ' guest1 ', ' 123 ' );

2.创建登录 jsp 文件

在 web 目录下创建 login.jsp :

<%@ page language="java" contentType="text/html; charset=UTF-8"
         pageEncoding="UTF-8" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>登录</title>
</head>
<body>
<div class="login" style="text-align:center;">
    <fieldset>
        <legend>用户登录</legend>
        <br/>
        <form action="login" method="post" name="login">
            用户名：<input type="text" name="username"/> <br/> <br/> 密&nbsp;码：<input
                type="password" name="password"/> <br/> <br/> <input
                type="submit" value="登录"/>
        </form>
    </fieldset>
</div>

</body>
</html>

3.创建登录 servlet 处理登录请求

登录成功跳转预设 jsp 文件
所使用 JDBC 操作类参考下文

Java MySQL 连接:https://eslsuwen.github.io/2019/06/02/Java-MySQL/

登录失败则跳回 login.jsp

package login;

import database.JdbcOp;

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

@WebServlet("/login")
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // 一般都会在doGet()方法中调用doPost()方法，或者在doPost()方法中调用doGet()方法
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // 设置编码格式，可以防止乱码出现
        response.setContentType("text/html; charset=utf-8");
        response.setCharacterEncoding("utf-8");
        request.setCharacterEncoding("utf-8");
        // 获取用户提交过来的用户名和密码，是通过表单中input的name属性获取的
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String isSignUp = request.getParameter("isSignUp");
        PrintWriter out = response.getWriter();
        System.out.println(username + ": " + password + " isSignUp: " + isSignUp);
        // 获取输出流，用户显示信息，也可以用转发或者重定向
        PrintWriter pw = response.getWriter();


        try {
            JdbcOp jdbc = new JdbcOp();
            jdbc.open("usersdb");
            ResultSet rs = jdbc.executeQuery("select * from users");

            while (rs.next()) {
                String nm = rs.getString("name");
                String pd = rs.getString("password");
                System.out.println("username: " + nm + " password: " + pd);

                if (nm.equals(username) && pd.equals(password)) {
                    HttpSession session = request.getSession();
                    //将数据存储到session中
                    session.setAttribute("isLogin", "true");
                    session.setAttribute("username", username);

                    out.print("<script language='javascript'>alert('You login successful  ! 你已成功登录！out.print');window.location.href='test.jsp';</script>");
                    out.flush();
                    out.close();
                }
            }
            jdbc.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        pw.write("login fail");
        out.print("<script language='javascript'>alert('please login first 登陆信息输入有误！');window.location.href='login.jsp';</script>");
        out.flush();
        out.close();
    }

}

4.运行项目

输入正确的账号密码：

账号密码验证失败：