Android程序開發通過HttpURLConnection上傳文件到服務器

 一：實現原理

最近在做Android客戶端的應用開發，涉及到要把圖片上傳到後台服務器中，自己選擇了做Spring3 MVC HTTP API作為後台上傳接口，android客戶端我選擇用HttpURLConnection來通過form提交文件數據實現上傳功能，本來想網上搜搜拷貝一下改改代碼就好啦，發現根本沒有現成的例子，多數的例子都是基於HttpClient的或者是基於Base64編碼以後作為字符串來傳輸圖像數據，於是我不得不自己動手，參考了網上一些資料，最終實現基於HttpURLConnection上傳文件的android客戶端代碼，廢話少說，其實基於HttpURLConnection實現文件上傳最關鍵的在於要熟悉Http協議相關知識，知道MIME文件塊在Http協議中的格式表示，基本的傳輸數據格式如下：

其中boundary表示form的邊界，只要按照格式把內容字節數寫到HttpURLConnection的對象輸出流中，服務器端的Spring Controller 就會自動響應接受，跟從浏覽器頁面上上傳文件是一樣的。

服務器端HTTP API， 我是基於Spring3 MVC實現的Controller，代碼如下：

@RequestMapping(value = "/uploadMyImage/{token}", method = RequestMethod.POST) 
public @ResponseBody String getUploadFile(HttpServletRequest request, HttpServletResponse response, 
@PathVariable String token) { 
logger.info("spring3 MVC upload file with Multipart form"); 
logger.info("servlet context path : " + request.getSession().getServletContext().getRealPath("/")); 
UserDto profileDto = userService.getUserByToken(token); 
String imgUUID = ""; 
try { 
if (request instanceof MultipartHttpServletRequest && profileDto.getToken() != null) { 
MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request; 
logger.info("spring3 MVC upload file with Multipart form"); 
// does not work, oh my god!! 
MultipartFile file = multipartRequest.getFiles("myfile").get(0); 
InputStream input = file.getInputStream(); 
long fileSize = file.getSize(); 
BufferedImage image = ImageIO.read(input); 
// create data transfer object 
ImageDto dto = new ImageDto(); 
dto.setCreateDate(new Date()); 
dto.setFileName(file.getOriginalFilename()); 
dto.setImage(image); 
dto.setCreator(profileDto.getUserName()); 
dto.setFileSize(fileSize); 
dto.setType(ImageAttachmentType.CLIENT_TYPE.getTitle()); 
dto.setUuid(UUID.randomUUID().toString()); 
/// save to DB 
imgUUID = imageService.createImage(dto); 
input.close(); 
} 
} catch (Exception e) { 
e.printStackTrace(); 
logger.error("upload image error", e); 
} 
return imgUUID; 
}

Android客戶端基於HttpURLConnection實現上傳的代碼，我把它封裝成一個單獨的類文件，這樣大家可以直接使用，只要傳入上傳的URL等參數即可。代碼如下：

package com.demo.http; 
import java.io.BufferedInputStream; 
import java.io.DataOutputStream; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import java.util.Random; 
import android.os.Handler; 
import android.util.Base64; 
import android.util.Log; 
public class UploadImageTask implements APIURLConstants { 
private String requestURL = DOMAIN_ADDRESS + UPLOAD_DESIGN_IMAGE_URL; // default 
private final String CRLF = "\r\n"; 
private Handler handler; 
private String token; 
public UploadImageTask(String token, Handler handler) { 
this.handler = handler; 
this.token = token; 
} 
public String execute(File...files) { 
InputStream inputStream = null; 
HttpURLConnection urlConnection = null; 
FileInputStream fileInput = null; 
DataOutputStream requestStream = null; 
handler.sendEmptyMessage(50); 
try { 
// open connection 
URL url = new URL(requestURL.replace("{token}", this.token)); 
urlConnection = (HttpURLConnection) url.openConnection(); 
// create random boundary 
Random random = new Random(); 
byte[] randomBytes = new byte[16]; 
random.nextBytes(randomBytes); 
String boundary = Base64.encodeToString(randomBytes, Base64.NO_WRAP); 
/* for POST request */ 
urlConnection.setDoOutput(true); 
urlConnection.setDoInput(true); 
urlConnection.setUseCaches(false); 
urlConnection.setRequestMethod("POST"); 
long size = (files[0].length() / 1024); 
if(size >= 1000) { 
handler.sendEmptyMessage(-150); 
return "error"; 
} 
// 構建Entity form 
urlConnection.setRequestProperty("Connection", "Keep-Alive"); 
urlConnection.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary); 
urlConnection.setRequestProperty("Cache-Control", "no-cache"); 
// never try to chunked mode, you need to set a lot of things 
// if(size > 400) { 
// urlConnection.setChunkedStreamingMode(0); 
// } 
// else { 
// urlConnection.setFixedLengthStreamingMode((int)files[0].length()); 
// } 
// end comment by zhigang on 2016-01-19 
/* upload file stream */ 
fileInput = new FileInputStream(files[0]); 
requestStream = new DataOutputStream(urlConnection.getOutputStream()); 
String nikeName = "myfile"; 
requestStream = new DataOutputStream(urlConnection.getOutputStream()); 
requestStream.writeBytes("--" + boundary + CRLF); 
requestStream.writeBytes("Content-Disposition: form-data; name=\"" + nikeName + "\"; filename=\"" + files[0].getName() + "\""+ CRLF); 
requestStream.writeBytes("Content-Type: " + getMIMEType(files[0]) + CRLF); 
requestStream.writeBytes(CRLF); 
// 寫圖像字節內容 
int bytesRead; 
byte[] buffer = new byte[8192]; 
handler.sendEmptyMessage(50); 
while((bytesRead = fileInput.read(buffer)) != -1) { 
requestStream.write(buffer, 0, bytesRead); 
} 
requestStream.flush(); 
requestStream.writeBytes(CRLF); 
requestStream.flush(); 
requestStream.writeBytes("--" + boundary + "--" + CRLF); 
requestStream.flush(); 
fileInput.close(); 
// try to get response 
int statusCode = urlConnection.getResponseCode(); 
if (statusCode == 200) { 
inputStream = new BufferedInputStream(urlConnection.getInputStream()); 
String imageuuId = HttpUtil.convertInputStreamToString(inputStream); 
Log.i("image-uuid", "uploaded image uuid : " + imageuuId); 
handler.sendEmptyMessage(50); 
return imageuuId; 
} 
} catch (Exception e) { 
e.printStackTrace(); 
} finally { 
if (inputStream != null) { 
try { 
inputStream.close(); 
} catch (IOException e) { 
e.printStackTrace(); 
} 
} 
if(requestStream != null) { 
try { 
requestStream.close(); 
} catch (IOException e) { 
e.printStackTrace(); 
} 
} 
if(fileInput != null) { 
try { 
fileInput.close(); 
} catch (IOException e) { 
e.printStackTrace(); 
} 
} 
if (urlConnection != null) { 
urlConnection.disconnect(); 
} 
} 
handler.sendEmptyMessage(50); 
return null; 
} 
private String getMIMEType(File file) { 
String fileName = file.getName(); 
if(fileName.endsWith("png") || fileName.endsWith("PNG")) { 
return "image/png"; 
} 
else { 
return "image/jpg"; 
} 
} 
}

經過本人測試，效果槓槓的！！所以請忘記HttpClient這個東西，android開發再也不需要它了。