核心代码

//login.html

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>登录</title>
</head>
<body>
<h1>请登录</h1>
<form action="/myProject/welcomeServlet" method="post">
    用户名：<input type="text" name="uname" id="uname"><br/>
    密&nbsp;码：<input type="password" name="upwd" id="upwd"><br/>
    <input type="submit" value="登录"><br/>
    <input type="reset" value="重置">
</form>
<div>
    &copy;2022&nbsp;<a href="https://sakurafeiyu.gitee.io">Sakurafeiyu</a>&nbsp;
</div>
</body>
</html>

//register.html

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>注册</title>
</head>
<body>
<h1>注册账号</h1>

<form action="/myProject/registerServlet" method="post">
    用户名<input type="text" placeholder="请输入用户名" id="uname" name="uname">
    密&nbsp;码<input type="password" placeholder="请输入密码" id="upwd" name="upwd">
    <input type="submit" value="提交">
</form>

</body>
</html>

//registerServlet

package cn.scit.htl.Servlet;

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 java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "registerServlet",urlPatterns = "/registerServlet")
public class registerServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println("<h1>注册成功！</h1>");
        String uname = request.getParameter("uname");
        String upwd = request.getParameter("upwd");
        out.println("<h2>您的个人信息，请妥善保存</h2>");
        out.println("用户名："+uname+"<br/>"+"密码："+upwd);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

//loginServlet

package cn.scit.htl.Servlet;

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 java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "welcomeServlet",urlPatterns = "/welcomeServlet")
public class welcomeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        String uname = request.getParameter("uname");
        String upwd = request.getParameter("upwd");
        if(("htl").equals(uname) && ("123456").equals(upwd)){
            out.println("<h1>尊敬的用户："+uname+"欢迎您&nbsp;&nbsp;</h1>");
            String myProject = "/myProject";
            out.print("<a href="+myProject+"></a>");
        }else{
            out.println("用户名或密码错误，请重试");
            response.sendRedirect("/myProject/login.html");

        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

实现效果

首页

登录页

注册页

总结与反思

在编写代码的过程中会有许多方法忘记，还需要加深印象；
注意代码编写过程中的拼写问题，注意大小写，有时候报错的问题可能不是别的，就是因为一个小小的错误，编写代码的时候一定要看仔细；
在配置tomcat的过程中比较曲折，IntelliJ IDEA 2021和2020好像又有所不同，在使用IDEA的过程中有点难受，配置“Edit Configurations”：
- 配置“Edit Configurations”，有许多坑
  - name名称随便取，注意Application server，选择你安装的tomcat，路径为你所安装tomcat的根目录
  - Open browser，选择运行的浏览器，随意
  - URL，项目访问统一资源符地址，一般是在主机名后接项目名称，像这样