ajax跨域访问的解决方案

时间：2022-08-14 06:22:51

　　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("&params="));

                          if(szPage.indexOf(".asp") == -1)

                          {

                              szPage = szPage.concat(".asp");

                          }

                          var szParam = szUrl.substring(szUrl.indexOf("&params=") + 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 {

        }

    }

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