package cn.hopetesting.com.servlet;
import com.fasterxml.jackson.databind.ObjectMapper;
import javax.print.attribute.standard.JobOriginatingUserName;
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;
/**
* @author newcityman
* @date 2019/9/18 - 21:49
*/
@WebServlet("/findUserServlet")
public class FindUserServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("application/json;charset=utf-8");
// response.setContentType("text/html;charset=utf-8");
//1、获取参数username
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：{
//("userExist:true,"msg","此用户名太受欢迎，请更换一个")，
// ("userExist:false,"msg","此用户名可用")}
Map<String,Object> map = new HashMap<String,Object>();
if("tom".equals(username)){
//存在
map.put("userExist",true);
map.put("msg","此用户名太受欢迎，请更换一个");
}else{
//不存在
map.put("userExist",false);
map.put("msg","此用户名可用");
}
//将map转换为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);
}
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>register</title>
<script src="js/jquery-3.3.1.min.js"></script>
<script>
//页面加载完成后
$(function () {
//给username绑定blur时间
$("#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：{
//("userExist:true,"msg","此用户名太受欢迎，请更换一个")，
// ("userExist:false,"msg","此用户名可用")}
$.get("findUserServlet",{username:username},function (data) {
//判断userExist键的值是否存在
var span = $("#s_username");
if(data.userExist){
//存在
span.css("color","red");
span.html(data.msg);
}else{
//不存在
span.css("color","green");
span.html(data.msg);
}
}/*,"json"*/);
});
});
</script>
</head>
<body>
<input type="text" id="username" name="username" placeholder="请输入用户名">
<span id="s_username"></span><br/>
<input type="password" id="password" name="passowrd" placeholder="请输入密码"><br/>
<input type="submit" value="提交">
</body>
</html>