ajax--用户信息的校验-优快云博客

本文链接：https://blog.youkuaiyun.com/tyutjavalily/article/details/47837671

本文介绍了一个简单的Servlet实现，用于验证用户输入的用户名是否已存在，并通过AJAX实时反馈验证结果。示例中Servlet接收请求参数并检查用户名是否存在于预定义列表中，然后返回相应的HTML格式消息。

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--Servlet代码

package com.ajax.servlets;

import java.io.IOException;
import java.util.Arrays;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/valiateUserName")
public class ValiateUserNameServlet extends HttpServlet {
	
	private static final long serialVersionUID = 1L;

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		List<String> userNames=Arrays.asList("AAA","BBB","CCC");
		String userName=request.getParameter("username");
		String result=null;
		
		if(userNames.contains(userName)){
			result="<font color='red'>该用户已经存在</font>";
		}else{
			result="<font color='green'>该用户已经可以使用</font>";
		}
		
		response.setContentType("text/html;charset=UTF-8");
		response.setCharacterEncoding("UTF-8");
		response.getWriter().print(result);
	}
}

jsp代码:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!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=ISO-8859-1">
<script type="text/javascript" src="${pageContext.request.contextPath}/scripts/jquery-1.7.2.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}/valiateUserName";
				var args={"username":val,"time":new Date()};
				
				$.post(url,args,function(data){
					
					$("#message").html(data);
				});
			}
		});
	})
</script>
<title>Insert title here</title>
</head>
<body>
	<form action="" method="post">
		username:<input type="text" name="username"/>
		<br>
		<div id="message"></div>
		<br>
		<input type="submit" value="submit"/>
	</form>
</body>
</html>