Ajax_Jason 使用小Demo 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/jquery-2.1.0.min.js"></script>
    <script>
        $(function () {
            $("#username").blur(function () {
                var user_name = $(this).val();
                //发送ajax请求    1请求资源路径 重点注意！路径不需要写反斜杠 /  2参数{} 3回调函数:返回值调用的函数
                $.get("findUserServlet",{username:user_name},function (data) {

                    //期望d返回的数据格式是：{“userExsit”： true ，“msg"："用户名存在"}
                                   //{“userExsit”： fase ，“msg"："用户名不存在"}

                    if(data.userExsit){
                        $("#user_").css("color","red");
                        $("#user_").html(data.msg);
                    }else {
                        $("#user_").html(data.msg);
                    }
                },"json") //“json”_指定返回数据的格式，不然就会把返回的数据当做字符串格式，不会当做json对象格式！ 那么就无法获取对应的值了
                          //或者在 服务器端指定MEMI类型： response.setContentType("application/json;charset=utf-8")
            });
        });
    </script>

</head>
<body>
    <form>
        <input type="text" id="username" name="username" placeholder="请输入用户名"><span id="user_"></span><br/>
        <input type="password" id="psd" name="psd" placeholder="请输入密码"><br/>
        <input type="submit" value="注册">
    </form>
</body>
</html>

 

请求的服务端

package 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 {
        doGet(request, response);
    }

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

        //response.setContentType("text/html;charset=utf-8");
        response.setContentType("application/json;charset=utf-8");


        String username = request.getParameter("username");
        System.out.println(username);
        Map<String,Object> map = new HashMap<String,Object>();

        if(username.equals("tom")) {
            map.put("userExsit",true);
            map.put("msg","用户名存在");
        }else {
            map.put("userExsit",false);
            map.put("msg","用户名不存在");
        }

        //将其用JackSom工具 写成jason格式传输出去  使用前需要导入jackson的jar包
        ObjectMapper ob = new ObjectMapper();
        ob.writeValue(response.getWriter(),map);  //想要返回去的数据要客户端当做 json数据看待的话必须设置 response.setContentType("application/json;charset=utf-8")
                                                  //或者在客服端页面的ajax请求的数据类型写成 “json”
    }
}

 

posted @ 2020-09-26 21:49  gaoshengjun  阅读(152)  评论(0)  编辑  收藏  举报