编写Servlet，验证用户登录，如果用户名与密码都为“admin”则验证通过，跳转欢迎页面，否则弹出提示信息“用户名或密码错误，请重新输入！”，点击“确定”后跳转至登录页面

java代码:(Test1)

package com.test;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet(urlPatterns={"/Test1"})

public class test1 extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        // TODO 自动生成的方法存根

        req.setCharacterEncoding("gbk");

        resp.setContentType("text/html;charset=utf-8");

        PrintWriter out = resp.getWriter();

        String user=req.getParameter("user");

        String pass = req.getParameter("pwd");

        if(user.equals("admin")&&pass.equals("admin")){

            out.println("欢迎登陆");

        }else{

            out.println("<script language='javascript'>alert('用户名或密码错误，请重新输入！')</script>");

            out.println("<script language='javascript'>window.location.href='/Servlet_work/Html1.html'</script>");

        }

    }

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        // TODO 自动生成的方法存根

        doGet(req, resp);

    }

}

html代码:(html1)

<!DOCTYPE html>

<html>

    <head>

        <title>Html1.html</title>

        <meta name="keywords" content="keyword1,keyword2,keyword3">

        <meta name="description" content="this is my page">

        <meta name="content-type" content="text/html; charset=utf-8">

        <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->

        <style>

            #home {

                width: 300px;

                height: 300px;

                margin: auto;

            }

            .dl1{

                clear: both;

            }

            .dl1 dt{

                float: left;

            }

            .dd1 dd{

                float: left;

            }

            h1{

                text-align: center;

            }

            #foot{

                text-align: center;

            }

        </style>

    </head>

    <body>

        <div id="home">

            <h1>用户登陆</h1>

            <form action="Test1" method="post">

                <dl class="dl1">

                    <dt>用户账号:</dt>

                    <dd><input type="text" name="user" /></dd>

                </dl>

                <dl class="dl1">

                    <dt>用户密码:</dt>

                    <dd><input type="passWord" name="pwd" /></dd>

                </dl>

                <div id="foot">

                <input type="submit" value="登陆"/>

                </div>

            </form>

        </div>

    </body>

</html>

运行截图:

编写Servlet，验证用户登录，如果用户名与密码都为“admin”则验证通过，跳转欢迎页面，否则弹出提示信息“用户名或密码错误，请重新输入！”，点击“确定”后跳转至登录页面

备注:

在Servlet中实现页面中弹窗:

PrintWriter out = resp.getWriter();

 out.println("<script language='javascript'>alert('用户名或密码错误，请重新输入！')</script>");

在Servlet中实现页面的跳转:

 out.println("<script language='javascript'>window.location.href='/Servlet_work/Html1.html'</script>");