jsp页面：
<%@ 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="${pageContext.request.contextPath }/scripts/jquery.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";
//Servlet获得的参数名为userName
var args = {"userName":val,"time":new Date()};
$.post(url,args,function(data){
$("#message").html(data);
})
}
});
})
</script>
</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>
servlet:
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;
/**
* Servlet implementation class ValiateUserName
*/
@WebServlet("/valiateUserName")
public class ValiateUserName extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public ValiateUserName() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request,HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException {
// TODO Auto-generated method stub
response.getWriter().append("Served at: ").append(request.getContextPath());
}
/**
* @see HttpServlet#doPost(HttpServletRequest request,HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request,IOException {
List<String> userNames = Arrays.asList("aaa","bbb","ccc");
String result = null;
String username = request.getParameter("userName");
if(userNames.contains(username)){
result = "<font color='red'>该用户已经被使用</font>";
}else{
result = "<font color='green'>该用户可以使用</font>";
}
response.setContentType("text/html;charset=utf-8");
response.setCharacterEncoding("utf-8");
response.getWriter().print(result);
}
}
