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在java中应用ajax，验证用户名，前台用js处理

2016-08-23 18:37 465 查看

前台的注册页面

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'register.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">


<script type="text/javascript">
function checkUserName(username) {
//将username传递到服务器,然后判断用户名是否已经存在
//<1>创建xmlHttpRequest对象:js发送请求到服务器
var xmlhttp;
if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp = new XMLHttpRequest();
} else {// code for IE6, IE5
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}

//<2>发送请求
//get请求
//xmlhttp.open("GET", "http://localhost:8090/filter/checkName.do?username="+username, true);

//post请求
xmlhttp.open("POST", "http://localhost:8080/filter/checkName.do", true);
//传递参数: set请求头 + 发送数据
xmlhttp.setRequestHeader("Content-type",
"application/x-www-form-urlencoded");
xmlhttp.send("username=" + username + "&password=admin");

//<3>响应:获取数据
// readyState=4 && status = 200
//onreadstatechange : (属性)事件,在readstate发生改变时触发
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
//请求成功而且获取到了数据
var response = xmlhttp.responseText;

response = JSON.parse(response);
//显示
if (response.flag) {
document.getElementById("user_info").innerHTML = response.content;
}
}
};

}
</script>

</head>

<body>
<form action="register.do" method="post">
用户名:<input type="text" name="username"
onblur="checkUserName(this.value)" /><span id="user_info"></span><br />
密码:<input type="password" name="password"><br /> 个性签名:<input
type="text" name="sign"><br /> <input type="submit"
value="注册"><br />
</form>
<br>
</body>
</html>

后台的servlet

import java.io.IOException;
import java.io.PrintWriter;

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

public class CheckNameServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");

System.out.println(username);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");

System.out.println(username);
System.out.println(password);

String msg = "";
if (username.equals("admin")) {
// 用户已存
msg = "{\"content\":\"用户已存在\",\"flag\":true}";
} else {
// 用户不存在
msg = "{\"content\":\"用户不存在\",\"flag\":false}";
}
response.getWriter().write(msg);
}

}

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标签： ajax

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