1.jsp代码
<%@ 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 }/js/jquery-1.9.1.min.js"></script>
<script type="text/javascript">
$(function() {
$(":input[name='name']").change(function() {
var val = $(this).val();
val = $.trim(val);
if (val != "") {
var url = "${pageContext.request.contextPath}/userName";
var args = {
"name" : val,
"time" : new Date()
};
$.post(url, args, function(data) {
$("#sj").html(data);
})
}
})
})
</script>
</head>
<body>
<form action="" method="post">
name:<input type="text" name="name" /> <br> <br>
<div id="sj"></div>
<input type="submit" value="提交" />
</form>
</body>
</html>
2.servlet代码
package he.bdqn.ajax;
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 UserName
*/
@WebServlet("/userName")
public class UserName extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
List<String> names = Arrays.asList("aa", "bb", "cc");
String name = request.getParameter("name");
String result = null;
if (names.contains(name)) {
result = "<font color='red'>用户名被使用</font>";
} else {
result = "<font color='green'>用户名可以使用</font>";
}
response.setContentType("text/html");
response.setCharacterEncoding("utf-8");
response.getWriter().print(result);
}
}