基于ＨＴＴＰ协议的多个文件上传

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

public class FileUpload extends AsyncTask {
	public  static final String TAG = "FileUpload";
	String actionUrl;
	Map<String, String> params;
	Map<String, File> files;
	UploadListener listener;
	
	public interface UploadListener {
		public void onUploadEnd(boolean success,String object);
	}
	
	public FileUpload(String actionUrl, Map<String, String> params,Map<String, File> files,UploadListener listener) {
		Log.i(TAG,"upload!");
		this.actionUrl = actionUrl;
		this.params = params;
		this.files = files;
		this.listener = listener;
	}
	
	@Override
	protected String doInBackground(Object... arg0) {
		String reslut = null;
		try {
			String BOUNDARY = java.util.UUID.randomUUID().toString();  
		     String PREFIX = "--", LINEND = "\r\n";  
		     String MULTIPART_FROM_DATA = "multipart/form-data";  
		     String CHARSET = "UTF-8";  
		     URL uri = new URL(actionUrl);  
		     HttpURLConnection conn = (HttpURLConnection) uri.openConnection();  
		     conn.setReadTimeout(5 * 1000);  
		     conn.setDoInput(true);// 允许输入  
		     conn.setDoOutput(true);// 允许输出  
		     conn.setUseCaches(false);  
		     conn.setRequestMethod("POST"); // Post方式  
		     conn.setRequestProperty("connection", "keep-alive");  
		     conn.setRequestProperty("Charsert", "UTF-8");  
		     conn.setRequestProperty("Content-Type", MULTIPART_FROM_DATA  + ";boundary=" + BOUNDARY);  
		     // 首先组拼文本类型的参数  
		     StringBuilder sb = new StringBuilder();  
		     for (Map.Entry<String, String> entry : params.entrySet()) {  
		         sb.append(PREFIX);  
		         sb.append(BOUNDARY);  
		         sb.append(LINEND);  
		         sb.append("Content-Disposition: form-data; name=\"" + entry.getKey() + "\"" + LINEND);  
		         sb.append("Content-Type: text/plain; charset=" + CHARSET + LINEND);  
		         sb.append("Content-Transfer-Encoding: 8bit" + LINEND);  
		         sb.append(LINEND);  
		         sb.append(entry.getValue());  
		         sb.append(LINEND);  
		     }  
		     DataOutputStream outStream = new DataOutputStream(conn.getOutputStream());  
		     outStream.write(sb.toString().getBytes());  
		     
		     // 发送文件数据  
		     if (files != null)  
//		         for (Map.Entry<String, File> file : files.entrySet()) {  
		    	 for (String key : files.keySet()) {
		             StringBuilder sb1 = new StringBuilder();  
		             sb1.append(PREFIX);  
		             sb1.append(BOUNDARY);  
		             sb1.append(LINEND);  
		             sb1.append("Content-Disposition: form-data; name=\"file\"; filename=\""   + key + "\"" + LINEND);  
		             sb1.append("Content-Type: multipart/form-data; charset="  + CHARSET + LINEND);  
		             sb1.append(LINEND);
		             outStream.write(sb1.toString().getBytes());  
		             File valuefile = files.get(key);
		             InputStream is = new FileInputStream(valuefile);  
		             byte[] buffer = new byte[1024];  
		             int len = 0;  
		             while ((len = is.read(buffer)) != -1) {  
		                 outStream.write(buffer, 0, len);  
		             }  
		             is.close();  
		             outStream.write(LINEND.getBytes());  
		         }
		     // 请求结束标志  
		     byte[] end_data = (PREFIX + BOUNDARY + PREFIX + LINEND).getBytes();  
		     outStream.write(end_data);  
		     outStream.flush();  
		     // 得到响应码  
//		     success = conn.getResponseCode()==200;  
		     

		     InputStream in = conn.getInputStream();  
		     InputStreamReader isReader = new InputStreamReader(in);  
		     BufferedReader bufReader = new BufferedReader(isReader);  
		     String line = null;  
		     reslut = "";  
		     while ((line = bufReader.readLine()) != null)  
		    	 reslut += line;  
		     outStream.close();   
		     conn.disconnect();  
		} catch (Exception e) {
			e.printStackTrace();
		} 
		return reslut;
	}
	
	@Override
	protected void onPreExecute() {
		//onPreExecute方法用于在执行后台任务前做一些UI操作  
		Log.i(TAG, "onPreExecute() called");  
	}
	
	@Override
	protected void onCancelled() {
		//取消操作
		Log.i(TAG, "onCancelled() called");  
		if (listener!=null) {
				listener.onUploadEnd(false, null);
		}
	}

	@Override
	protected void onPostExecute(Object result) {
		//onPostExecute方法用于在执行完后台任务后更新UI,显示结果  
		Log.i(TAG, "onPostExecute(Result result) called");  
		if (listener!=null) {
			if (result==null) {
				listener.onUploadEnd(false, null);
			} else {
				listener.onUploadEnd(true,  result.toString());
			}
 		}
	}
	

	@Override
	protected void onProgressUpdate(Object... values) {
		 //onProgressUpdate方法用于更新进度信息  
		Log.i(TAG, "onProgressUpdate() called");  
	}
 
	
}

本文分析部分来源：http://blog.youkuaiyun.com/skyer_lei/article/details/6106709，代码由本人编写，转发请注明，谢谢！