利用HttpURLConnection发送post请求上传多个文件

转自skyer_lei的专栏:http://blog.csdn.net/skyer_lei/article/details/6106709

本文要用java.net.HttpURLConnection来实现多个文件上传

1. 研究 form 表单到底封装了什么样的信息发送到servlet。

假如我参数写的内容是hello word,然后二个文件是二个简单的txt文件，form提交的信息为：

 -----------------------------7da2e536604c8
 Content-Disposition: form-data; name="username"

 hello word
 -----------------------------7da2e536604c8
 Content-Disposition: form-data; name="file1"; filename="D:/haha.txt"
 Content-Type: text/plain

 haha
   hahaha
 -----------------------------7da2e536604c8
 Content-Disposition: form-data; name="file2"; filename="D:/huhu.txt"
 Content-Type: text/plain

 messi
 huhu
 -----------------------------7da2e536604c8--

 

 

研究下规律发现有如下几点特征

1.第一行是“ -----------------------------7d92221b604bc ”作为分隔符，然后是“ /r/n ” 回车换行符。 这个7d92221b604bc 分隔符浏览器是随机生成的。

2.第二行是Content-Disposition: form-data; name="file2"; filename="D:/huhu.txt";name=对应input的name值，filename对应要上传的文件名（包括路径在内），

3.第三行如果是文件就有Content-Type: text/plain；这里上传的是txt文件所以是text/plain,如果上穿的是jpg图片的话就是image/jpg了，可以自己试试看看。

然后就是回车换行符。

4.在下就是文件或参数的内容或值了。如：hello word。

5.最后一行是-----------------------------7da2e536604c8--,注意最后多了二个--;

有了这些就可以使用HttpURLConnection来实现上传文件功能了

 private void upload(String[] uploadFiles, String actionUrl) {
       String end = "/r/n";
       String twoHyphens = "--";
       String boundary = "*****";
       try {
           URL url = new URL(actionUrl);
           HttpURLConnection con = (HttpURLConnection) url.openConnection();
            // 发送POST请求必须设置如下两行
           con.setDoInput(true);
           con.setDoOutput(true);
           con.setUseCaches(false);
           con.setRequestMethod("POST");
           con.setRequestProperty("Connection", "Keep-Alive");
           con.setRequestProperty("Charset", "UTF-8");
           con.setRequestProperty("Content-Type",
                   "multipart/form-data;boundary=" + boundary);
           DataOutputStream ds =
                   new DataOutputStream(con.getOutputStream());
           for (int i = 0; i < uploadFiles.length; i++) {
               String uploadFile = uploadFiles[i];
               String filename = uploadFile.substring(uploadFile.lastIndexOf("//") + 1);
               ds.writeBytes(twoHyphens + boundary + end);
               ds.writeBytes("Content-Disposition: form-data; " +
                       "name=/"file" + i + "/";filename=/"" +
                       filename + "/"" + end);
               ds.writeBytes(end);
               FileInputStream fStream = new FileInputStream(uploadFile);
               int bufferSize = 1024;
               byte[] buffer = new byte[bufferSize];
               int length = -1;
               while ((length = fStream.read(buffer)) != -1) {
                   ds.write(buffer, 0, length);
               }
               ds.writeBytes(end);
               /* close streams */
               fStream.close();
           }
           ds.writeBytes(twoHyphens + boundary + twoHyphens + end);
           ds.flush();
           // 定义BufferedReader输入流来读取URL的响应
           InputStream is = con.getInputStream();
           int ch;
           StringBuffer b = new StringBuffer();
           while ((ch = is.read()) != -1) {
               b.append((char) ch);
           }
           String s = b.toString();
           if (s.contains("successfully")) {
               // for (int i = 1; i < 5; i++) {
               int beginIndex = s.indexOf("url =") + 5;
               int endIndex = s.indexOf("/n", beginIndex);
               String urlStr = s.substring(beginIndex, endIndex).trim();
               System.out.println(urlStr);
               // }
           }
           ds.close();
       } catch (Exception e) {
       }
   }

 

 

 至于接收文件上传的服务，以后再写