今天的工作中要访问摄像机内部的一个web站点，这就涉及到jquery的ajax跨域访问的问题。我使用的是jquery1.7的版本，下面总结如下：
- 问题一：
一开始用IE调试，总是返回No Transport错误，这是因为在进行跨域访问的时候，IE8浏览器（不同的浏览器对跨域的支持不一样）不支持跨域访问，必须在ajax请求前面加上 jQuery.support.cors = true;才行。 - 问题二：跨域问题解决后，返回的xhr.statusText = "[object Error]"，并且xmlHttpReqest.readyState始终为0。
后来我更改为自己的url，可以访问，说明是跨域的问题。后来我不用jquery的ajax，用最原始的ajax在执行到open函数的时候，提示没有权限。这才知道是跨域访问没有权限的问题。
后来在项目组同事的帮助下找到了下面的解决方案：
就是通过吧url和参数发送给servlet，然后servlet再建立HttpURLConnection，把请求发送给其他的站点。当然我们的项目为了把所有发送的请求都对应一个servlet，使用的是过滤器。
first.jsp：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<link href="IEfile/doc/css/base.css" rel="stylesheet" type="text/css" />
<link href="IEfile/doc/css/login.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="IEfile/doc/script/jquery-1.7.1.min.js"></script>
<script type="text/javascript" src="IEfile/doc/script/jquery.cookie.js"></script>
<script type="text/javascript" src="IEfile/doc/script/login.js"></script>
<script type="text/javascript" src="IEfile/doc/script/common.js"></script>
<script type="text/javascript" src="IEfile/doc/script/Translator.js"></script> <script type="text/javascript">
var g_lxdLogin = null; // Login.xml
function DoLogin()
{
m_szUserPwdValue = "111";//Base64.encode("admin" + ":" + "12345");
var m_lHttp = "http://";
var m_szHostName = "localhost";
var m_lHttpPort = "8080";
var urlTest = m_lHttp + m_szHostName + ":" + m_lHttpPort + "/WebServerTest1/PSIA/Custom/SelfExt/userCheck";
alert(urlTest);
$.ajax({
type: "GET",
url: urlTest,
async: true,
timeout: 15000,
beforeSend: function(xhr) {
xhr.setRequestHeader("If-Modified-Since", "0");
xhr.setRequestHeader("Authorization", "Basic " + m_szUserPwdValue);
},
success: function(xmlDoc, textStatus, xhr)
{
alert("login success");
if("200" == xmlDoc.documentElement.getElementsByTagName('statusValue')[0].childNodes[0].nodeValue)
{
var szUrl = decodeURI(document.URL);
if(szUrl.indexOf("?page=") != -1)
{
var szPage = szUrl.substring(szUrl.indexOf("page=") + 5, szUrl.indexOf("¶ms="));
if(szPage.indexOf(".asp") == -1)
{
szPage = szPage.concat(".asp");
}
var szParam = szUrl.substring(szUrl.indexOf("¶ms=") + 8, szUrl.length);
$.cookie('page',szPage+"?"+szParam+"%1");
}
else
{
$.cookie('page',null);
} $.cookie('userInfo'+m_lHttpPort,m_szUserPwdValue==""?Base64.encode("anonymous:\177\177\177\177\177\177"):m_szUserPwdValue);
window.location.href = "main.asp";
}
else
{
if(!$('#UserName').prop("disabled")) {
$('#UserName').focus();
}
$('#UserName').val('');
$('#Password').val('');
alert(translator.translateNode(g_lxdLogin, 'LoginTips4'));
}
},
error: function(xhr, textStatus, errorThrown)
{
alert("login error = " + textStatus);
if("timeout" == textStatus)
{
alert(translator.translateNode(g_lxdLogin, 'ConnectTimeoutTips'));
}
else
{
alert(translator.translateNode(g_lxdLogin, 'NetworkErrorTips'));
}
}
});
}
</script>
</head> <body >
<input type="button" name="b" value="TestJson" onclick="DoLogin()"/>
</body> </html>
web.xml：
<!-- psia过滤器 -->
<filter>
<filter-name>psiaFilter</filter-name>
<filter-class>com.zm.servlet.psiaFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>psiaFilter</filter-name>
<url-pattern>/PSIA/*</url-pattern>
</filter-mapping> <!-- 起始页面-->
<welcome-file-list>
<welcome-file>/IEfile/doc/page/first.jsp</welcome-file>
</welcome-file-list>
psiaFilter.java：
package com.zm.servlet; import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection; import javax.servlet.*;
import javax.servlet.http.*; public class psiaFilter implements javax.servlet.Filter { public void destroy() {
} public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException { HttpServletRequest req = (HttpServletRequest)(request);
String uri = req.getRequestURI();
uri = uri.substring(15);
String Auth = req.getHeader("Authorization");
String method = req.getMethod();
HttpServletResponse res = (HttpServletResponse)(response); //((HttpServletResponse)(response)).sendError(700, "psiaFilter" + uri + Auth); String url= "http://172.16.8.178" + uri;
URL theURL = new URL(url);
HttpURLConnection urlConnection = (HttpURLConnection)theURL.openConnection(); urlConnection.setReadTimeout(11);
urlConnection.setRequestMethod(method);
urlConnection.setRequestProperty("If-Modified-Since", "0");
urlConnection.setRequestProperty("Authorization", Auth);
urlConnection.connect(); PrintWriter out = res.getWriter();
//out.println(url); InputStream in = urlConnection.getInputStream();
int c;
while((c = in.read()) != -1)
out.write(c);
System.out.println(out.toString());
//chain.doFilter(request, response);
} public void init(FilterConfig arg0) throws ServletException {
} }