（1）取得服务端当前时间
jquery对象.load(url,sendData,function(backData,textStatus,xhr){... ...})
load()：如果无参的话，就以GET方式发送
如果有参的话，就以POST方式发送
（2）检查注册用户名是否存在
$.get(url,sendData,function(backData,textStatus,xhr){... ...})
$.post(url,sendData,function(backData,textStatus,xhr){... ...})
getTime.jsp
<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script type="text/javascript" src="js/jquery-1.8.2.js"></script>
</head>
<body>
<input type="button" value="获取时间"/>
<hr/>
<div></div>
<script type="text/javascript">
$(":button").click(function(){
/*
url表示异步请求的路径
sendData表示发送的数据，该数据的格式为{"key":value,"key":value}
function(){}表示回调处理函数，由服务端触发，类似于xhr.onreadystatechange
*/
var url = "/jsExamples/TimeServlet?time="+new Date().getTime();
var sendData = {"username":"杰克","password":"102030"};
//哪个jquery对象调用load()方法，
//返回值就设置到这个jquery对象的html()方法中
$("div").load(url,sendData,function(backData,textStatus,xhr){
alert(backData+":"+textStatus+":"+xhr.status)
});
});
</script>
</body>
</html>
TimeServlet.java
package cn.itcast.web.servlet; import java.io.IOException;
import java.text.DateFormat;
import java.util.Date;
import java.util.Locale;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class TimeServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
DateFormat df = DateFormat.getDateTimeInstance(
DateFormat.FULL,
DateFormat.DEFAULT,
Locale.CHINA);
String now = df.format(new Date());
response.setContentType("text/html;charset=UTF-8");
response.getWriter().write(now);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
String ip = request.getRemoteAddr();
if(ip.equals("127.0.0.1")){
String username = request.getParameter("username");
String password = request.getParameter("password");
response.getWriter().write(username+":"+password);
}
}
}
ajax_2.jsp 调用$.get()方法
<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script type="text/javascript" src="js/jquery-1.8.2.js"></script>
</head>
<body>
用户名[GET]：<input type="text"/><span></span>
<script type="text/javascript">
$(":text").blur(function(){
//获取用户在文本框中填入的值
var username = $(this).val();
//去空格
username = $.trim(username);
//判断
if(username==null || username.length==0){
$("span").html("用户名必填");
}else{
/*
回调函数有三个参数：
backData:表示服务端返回的数据
textStatus:表示服务端返回的数据的文本表达，如果成功，返回success
xhr:表示ajax引警对象
*/
var url = "/day30/UserServlet?time="+new Date().getTime();
var sendData = {"username":username};
$.get(url,sendData,function(backData,textStatus,xhr){
//定位span标签
var $span = $("span");
//将清span标签中的内容
$span.html("");
//创建img标签
var $img = $("<img src='" + backData + "'/>")
//将img标签设置到span标签内部，形成父子关系
$span.append( $img );
});
}
});
</script>
</body>
</html>
ajax_3.jsp调用 $.post()方法
<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script type="text/javascript" src="js/jquery-1.8.2.js"></script>
</head>
<body>
用户名[POST]：<input type="text" name="username"/>
<span></span>
<script type="text/javascript">
$(":text").blur(function(){
//获取用户在文本框中填入的值
var username = $(this).val();
//去空格
username = $.trim(username);
//判断
if(username==null || username.length==0){
$("span").html("<font color='red'><b>用户名必填</b></font>");
}else{
/*
回调函数有三个参数：
backData:表示服务端返回的数据
textStatus:表示服务端返回的数据的文本表达，如果成功，返回success
xhr:表示ajax引警对象
*/
var url = "/day30/UserServlet?time="+new Date().getTime();
//var sendData = {"username":username};传统
var sendData = $(":text").serialize();//优化
$.post(url,sendData,function(backData,textStatus,xhr){
//定位span标签
var $span = $("span");
//将清span标签中的内容
$span.html("");
//创建img标签
var $img = $("<img width='30' height='30' src='" + backData + "'/>")
//将img标签设置到span标签内部，形成父子关系
$span.append( $img );
});
}
});
</script>
</body>
</html>
UserServlet.java
package cn.itcast.web.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 UserServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
String username = request.getParameter("username");
byte[] buf = username.getBytes("ISO8859-1");
username = new String(buf,"UTF-8");
String imagePath = "images/MsgSent.gif";
if("哈哈".equals(username)){
imagePath = "images/MsgError.gif";
}
response.setContentType("text/html;charset=UTF-8");
response.getWriter().write(imagePath);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
String username = request.getParameter("username");
String imagePath = "images/MsgSent.gif";
if("哈哈".equals(username)){
imagePath = "images/MsgError.gif";
}
response.setContentType("text/html;charset=UTF-8");
response.getWriter().write(imagePath);
}
}