JavaWeb校验用户名小案例(Ajax实现,未连接数据库)

 

设定数据库种已存在的用户名为" Tom " ,若在注册用户名表单中输入 " Tom " 则显示此用户名已被使用 ,若不是 " Tom " 则显示用户名可用。

仅包含一个html页面和一个servlet,此案例仅用于学习Ajax。

使用Jackson技术。需导入外部Jar包

 

 

Html代码:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
    <script src="js/jquery-3.3.1.min.js"></script>


    <script>
        //在页面加载完成后
        $(function () {
           //给username绑定blur事件
           $("#username").blur(function () {
               //获取username文本输入框的值
               var username = $(this).val();
               //发送ajax请求
               //期望服务器响应回的数据格式:{"userExsit":true,"msg":"此用户名太受欢迎,请更换一个"}
               //                         {"userExsit":false,"msg":"用户名可用"}
               $.get("findUserServlet",{username:username},function (data) {
                   //判断userExsit键的值是否是true

                   // alert(data);
                   var span = $("#s_username");
                   if(data.userExsit){
                       //用户名存在
                       span.css("color","red");
                       span.html(data.msg);
                   }else{
                       //用户名不存在
                       span.css("color","green");
                       span.html(data.msg);
                   }
               });

           }); 
        });

    </script>
</head>
<body>


    <form>

        <input type="text" id="username" name="username" placeholder="请输入用户名">
        <span id="s_username"></span>
        <br>
        <input type="password" name="password" placeholder="请输入密码"><br>
        <input type="submit" value="注册"><br>

    </form>

</body>
</html>

 

Servlet代码:

package cn.itcast.web.servlet;

import com.fasterxml.jackson.databind.ObjectMapper;

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.util.HashMap;
import java.util.Map;

@WebServlet("/findUserServlet")
public class FindUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取用户名
        String username = request.getParameter("username");

        //2.调用service层判断用户名是否存在

        //期望服务器响应回的数据格式:{"userExsit":true,"msg":"此用户名太受欢迎,请更换一个"}
        //                         {"userExsit":false,"msg":"用户名可用"}

        //设置响应的数据格式为json
        response.setContentType("application/json;charset=utf-8");
        Map<String,Object> map = new HashMap<String,Object>();

        if("tom".equals(username)){
            //存在
            map.put("userExsit",true);
            map.put("msg","此用户名太受欢迎,请更换一个");
        }else{
            //不存在
            map.put("userExsit",false);
            map.put("msg","用户名可用");
        }

        //将map转为json,并且传递给客户端
        //将map转为json
        ObjectMapper mapper = new ObjectMapper();
        //并且传递给客户端
        mapper.writeValue(response.getWriter(),map);


    }

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

 

posted @ 2020-02-01 14:05  RomanticChopin  阅读(177)  评论(0编辑  收藏  举报
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