006 ajax验证用户名

1.大纲

2.index.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"

     pageEncoding="UTF-8"%>

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

 <title>Insert title here</title>

 <script type="text/javascript" src="jquery-3.2.1.min.js"></script>

 <script type="text/javascript">

     $(function(){

         $(":input[name='userName']").change(function(){

             var val=$(this).val();

             val=$.trim(val);

             if(val!=""){

                 var url="${pageContext.request.contextPath}/ValidateUserName";

                 var args={"userName":val,"time":new Date()};

                 $.post(url,args,function(data){

                     $("#message").html(data);

                 })

             }

         })

     })

 </script>

 </head>

 <body>

     <form action="" method="get">

         UserName<input type="text" name="userName"/><br>

         <div id="message"></div><br><br>

         <input type="submit" value="SUBMIT"/>

     </form>

 </body>

 </html>

3.ValidateUserName.java

 package servlets;

 import java.io.IOException;

 import java.util.Arrays;

 import java.util.List;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 public class ValidateUserName extends HttpServlet{

     private static final long serialVersionUID = 1L;

     @Override

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

         List<String> userNames=Arrays.asList("A","B","C");

         String userName=request.getParameter("userName");

         String result=null;

         if(userNames.contains(userName)) {

             result="<font color='red'>改用户被用</font>";

         }else {

             result="<font color='green'>改用户可以使用</font>";

         }

         response.setContentType("text/html;charset=UTF-8");

         response.setCharacterEncoding("UTF-8");

         response.getWriter().print(result);

     }

 }

4.web.xml映射

 <?xml version="1.0" encoding="UTF-8"?>

 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">

   <display-name>newDynamicProjectTest</display-name>

   <servlet>

         <servlet-name>ValidateUser</servlet-name>

         <servlet-class>servlets.ValidateUserName</servlet-class>

   </servlet>

   <servlet-mapping>

        <servlet-name>ValidateUser</servlet-name>

        <url-pattern>/ValidateUserName</url-pattern>

   </servlet-mapping>

 </web-app>

5.效果

巴特西

006 ajax验证用户名

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