本系列博客汇总在这里:AJAX 汇总
AJAX 的 get 请求
- 一、前端页面
- 二、后台 servlet
- 三、配置文件 web.xml
- 四、效果展示
一、前端页面
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
//定义xmlhttprequest
var xmlHttp;
function ajaxFunction()
{
try
{
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
try
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e)
{
alert("您的浏览器不支持AJAX!");
return false;
}
}
}
}
function validUser(obj)
{
//创建XMLHttpRequest
ajaxFunction();
var url = "/ajax_demo/valid?username="+obj.value;
//打开连接,第一个参数是请求方式,第二个参数是请求地址,第三个参数是同步还是异步,true同步,false是异步
xmlHttp.open('get', url, false);
//接受服务器 的响应
xmlHttp.onreadystatechange = _callback;
//发送数据,如果是get请求数据是在url上传递,不需要发送数据,send必须在最后调用。
xmlHttp.send(null);
}
function _callback()
{
//readyState==4请求完成
if(xmlHttp.readyState == 4)
{
//服务器响应正确
if(xmlHttp.status == 200)
{
//接收服务器的响应数据
var result = xmlHttp.responseText;
if(result == 'error')
{
document.getElementById('tip').innerHTML = '用户名已存在';
}
else
{
document.getElementById('tip').innerHTML = '';
}
}
}
}
</script>
</head>
<body>
<form>
<table>
<tr>
<td>用户名</td>
<td><input id="username" type="text" onblur="validUser(this)"><span id='tip'></span></td>
</tr>
</table>
</form>
</body>
</html>
二、后台 servlet
package cn.wyx.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ValidServlet extends HttpServlet
{
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
doPost(request, response);
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
String username = request.getParameter("username");
if("wyx".equals(username))
{
response.getWriter().print("error");
}
else
{
response.getWriter().print("ok");
}
}
}
三、配置文件 web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<servlet>
<servlet-name>ValidServlet</servlet-name>
<servlet-class>cn.wyx.servlet.ValidServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ValidServlet</servlet-name>
<url-pattern>/valid</url-pattern>
</servlet-mapping>
</web-app>
四、效果展示
如有错误,欢迎指正!