案例_校验用户名是否存在
服务器响应的数据 在客户端使用时 要想当做json数据格式使用
- $.get(type):将最后一个参数typer指定为“json”
- 在服务器端设置MIME类型
- response.setContentType("application/json;charset=utf-8");
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>
java代码
package com.bai.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 //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); } }标签:username,map,用户名,校验,案例,json,import,response From: https://www.cnblogs.com/aimz01/p/16610029.html