案例-验证用户是否存在

 

package com.itheima.web.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;

@WebServlet("/selectUserServlet")
public class SelectUserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 接收用户名
        String username = request.getParameter("username");

        //2. 调用service查询User对象
        //模拟成true
        boolean flag = true;

        //3. 响应标记
        response.getWriter().write(""+flag);

    }

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

}
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>欢迎注册</title>
    <link href="css/register.css" rel="stylesheet">
</head>
<body>

<div class="form-div">
    <div class="reg-content">
        <h1>欢迎注册</h1>
        <span>已有帐号？</span> <a href="login.html">登录</a>
    </div>
    <form id="reg-form" action="#" method="get">

        <table>

            <tr>
                <td>用户名</td>
                <td class="inputs">
                    <input name="username" type="text" id="username">
                    <br>
                    <span id="username_err" class="err_msg" style="display: none">用户名已存在</span>
                </td>

            </tr>

            <tr>
                <td>密码</td>
                <td class="inputs">
                    <input name="password" type="password" id="password">
                    <br>
                    <span id="password_err" class="err_msg" style="display: none">密码格式有误</span>
                </td>
            </tr>


            <tr>
                <td>验证码</td>
                <td class="inputs">
                    <input name="checkCode" type="text" id="checkCode">
                    <img src="imgs/a.jpg">
                    <a href="#" id="changeImg">看不清？</a>
                </td>
            </tr>

        </table>

        <div class="buttons">
            <input value="注 册" type="submit" id="reg_btn">
        </div>
        <br class="clear">
    </form>

</div>
<script>
    //1.给用户名输入框绑定 失去焦点事件onblur
    document.getElementById("username").onblur = function () {
        //2. 发送AJAX请求
        //获取用户名的值
        var username = this.value;

        //2.1. 创建核心对象
        var xhttp;
        if (window.XMLHttpRequest){
            xhttp = new XMLHttpRequest();
        }else {
            //code for IE6 IE5
            xhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        //2.2. 发送请求
        xhttp.open("GET","http://localhost:8080/ajax-demo/selectUserServlet?username="+username);
        xhttp.send();

        //2.3. 获取响应
        xhttp.onreadystatechange = function () {
            if (xhttp.readyState == 4 && xhttp.status == 200){
                // alert(xhttp.responseText);
                //判断
                if (this.responseText == "true"){
                    //用户存在，显示提示信息
                    document.getElementById("username_err").style.display = '';//设置id为username_err的style的display属性为空字符串
                }else {
                    //用户不存在，清除提示信息
                    document.getElementById("username_err").style.display = 'none';//设置id为username_err的style的display属性为none
                }
            }
        }
    }
</script>
</body>
</html>

 

posted @ 2023-07-03 15:31  Karlshell  阅读(60)  评论(0)    收藏  举报