Html5 ajax的跨域请求

1、XMLHttpRequest升级版已经实现了跨域请求。不过需要在后台设置:header("Access-Control-Allow-Origin:http://www.a.com");表示某个域下允许跨域访问。

2、IE：需要使用XDomainRequest()。同样需要在后台设置：response.addHeader("Access-Control-Allow-Origin","*");

3、如果后台语言为java的话，需要自己写一个CrossDomainFilter，在过滤器中设置跨域访问，否则上传不成功。

下面以一个ajax文件上传的例子来说明跨域问题：

前台代码：

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="UTF-8">
 5         <title></title>
 6     </head>
 7     <body>
 8         <form action="" method="post" onsubmit="return false;">
 9             <input type="file" name="myFile" id="myFile" value=""/>
10             <input type="button" id="btn" value="上传" /><br />
11         </form>
12         <progress id="progress" max="100" value="0" style="margin-top:10px;"></progress>
13     </body>
14 </html>
15 <script type="text/javascript">
16     window.onload = function(){
17         var oBtn = document.getElementById("btn");
18         var oFile = document.getElementById("myFile");
19         var oProgress = document.getElementById("progress");
20         oBtn.onclick = function(){
21             if(oFile.files.length <=0)return;
22             //TODO:这里假定只是单文件上传
23             var formData = new FormData();
24             formData.append("file",oFile.files[0]);
25             
26             var xhr = new XMLHttpRequest();
27             xhr.upload.onprogress = function(ev){
28                 ev = ev || window.event;
29                 if(ev.lengthComputable)oProgress.value = parseInt(ev.loaded/ev.total*100);
30             }
31             xhr.upload.onload = function(){
32                 oProgress.value = 100;
33             }
34             xhr.open("POST","http://127.0.0.1:8080/ajax5.do",true);
35             xhr.send(formData);
36         }
37         
38     }
39 </script>

后台代码：

 1 package com.sgepit.ajax;
 2 
 3 import java.io.File;
 4 import java.io.IOException;
 5 import java.util.List;
 6 import java.util.UUID;
 7 
 8 import javax.servlet.ServletException;
 9 import javax.servlet.annotation.WebServlet;
10 import javax.servlet.http.HttpServlet;
11 import javax.servlet.http.HttpServletRequest;
12 import javax.servlet.http.HttpServletResponse;
13 import javax.servlet.http.HttpSessionContext;
14 
15 import org.apache.commons.fileupload.FileItem;
16 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
17 import org.apache.commons.fileupload.servlet.ServletFileUpload;
18 
19 
20 /**
21  * @author tengri
22  *文件上传
23  */
24 @SuppressWarnings("all")
25 @WebServlet("/ajax5.do")
26 public class Ajax5 extends HttpServlet {
27 
28     @Override
29     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
30         this.doPost(req, resp);
31     }
32     
33     @Override
34     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
35         DiskFileItemFactory factory = new DiskFileItemFactory();
36         factory.setSizeThreshold(2014 * 1024);
37         factory.setRepository(new File("D:/uploadTemp"));
38         ServletFileUpload upload = new ServletFileUpload(factory);
39         resp.setCharacterEncoding("utf-8");
40         try {
41             List<FileItem> items = upload.parseRequest(req);
42             for(FileItem item : items){
43                 if(!item.isFormField()){
44                     //文件名
45                     String fileName = item.getName();
46                     System.out.println(new String(fileName.getBytes(),"utf-8"));
47                     fileName = new String(fileName.getBytes(),"utf-8");
48                     //检查文件格式
49                     String fileEnd = fileName.substring(fileName.lastIndexOf(".")+1).toLowerCase();
50                     //真实上传路径
51                     StringBuffer sbRealPath = new StringBuffer();
52                     sbRealPath.append("D:/uploadFile/").append(fileName);
53                     File file = new File(sbRealPath.toString());
54                     item.write(file);
55                 }
56             }
57         } catch (Exception e) {
58             e.printStackTrace();
59         }
60     }
61 
62 }

过滤器：

package com.sgepit.ajax;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;

/**
 * @author tengri
 *跨域filter
 */
public class CrossDomainFilter implements Filter{

    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
            throws IOException, ServletException {
        HttpServletResponse res = (HttpServletResponse) resp;
        //这里最好不要写通配符，如果允许多个域请求数据的话，可以直接用逗号隔开："http://www.baidu.com,http://google.com"
        res.setHeader("Access-Control-Allow-Origin", "*");
        res.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS");
        res.setHeader("Access-Control-Allow-Headers", "Content-Type, Authorization, Accept,X-Requested-With");
        chain.doFilter(req, resp);
    }

    public void init(FilterConfig arg0) throws ServletException {
        
    }
}

web.xml配置过滤器：

1 <filter>
2       <filter-name>myFilter</filter-name>
3       <filter-class>com.sgepit.ajax.CrossDomainFilter</filter-class>
4   </filter>
5   <filter-mapping>
6       <filter-name>myFilter</filter-name>
7       <url-pattern>/*</url-pattern>
8   </filter-mapping>