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：
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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;
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插入一些数据：
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INSERT INTO `user`
VALUES
( ‘admin‘, ‘admin‘ ),
( ‘ guest ‘, ‘ 123456 ‘ ),
( ‘ guest1 ‘, ‘ 123 ‘ );
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2. 创建登录 jsp 文件
在 web 目录下创建 login.jsp :
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<%@ 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 码：<input
type="password" name="password"/> <br/> <br/> <input
type="submit" value="登录"/>
</form>
</fieldset>
</div>
</body>
</html>
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3. 创建登录 servlet 处理登录请求
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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();
}
}
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4. 运行项目
输入正确的账号密码：
账号密码验证失败：
