1，專案調研

因為需要研究下斷點上傳的問題。找了很久終於找到一個比較好的專案。

在GoogleCode上面，程式碼弄下來超級不方便，還是配置hosts才好，把程式碼重新上傳到了github上面。

效果：

上傳中，顯示進度，時間，百分比。

點選【Pause】暫停，點選【Resume】繼續。

2，程式碼分析

原始專案：

這個專案最後更新的時間是 2012 年，專案進行了封裝使用最簡單的方法實現了http的斷點上傳。

因為html5 裡面有讀取檔案分割檔案的類庫，所以才可以支援斷點上傳，所以這個只能在html5 支援的瀏覽器上面展示。

同時，在js 和 java 同時使用 cr32 進行檔案塊的校驗，保證資料上傳正確。

程式碼在使用了最新的servlet 3.0 的api，使用了非同步執行，監聽等方法。

上傳類UploadServlet

@Component("javaLargeFileUploaderServlet")
@WebServlet(name = "javaLargeFileUploaderServlet", urlPatterns = { "/javaLargeFileUploaderServlet" })
public class UploadServlet extends HttpRequestHandlerServlet
		implements HttpRequestHandler {

	private static final Logger log = LoggerFactory.getLogger(UploadServlet.class);

	@Autowired
	UploadProcessor uploadProcessor;

	@Autowired
	FileUploaderHelper fileUploaderHelper;

	@Autowired
	ExceptionCodeMappingHelper exceptionCodeMappingHelper;

	@Autowired
	Authorizer authorizer;

	@Autowired
	StaticStateIdentifierManager staticStateIdentifierManager;



	@Override
	public void handleRequest(HttpServletRequest request, HttpServletResponse response)
			throws IOException {
		log.trace("Handling request");

		Serializable jsonObject = null;
		try {
			// extract the action from the request
			UploadServletAction actionByParameterName =
					UploadServletAction.valueOf(fileUploaderHelper.getParameterValue(request, UploadServletParameter.action));

			// check authorization
			checkAuthorization(request, actionByParameterName);

			// then process the asked action
			jsonObject = processAction(actionByParameterName, request);


			// if something has to be written to the response
			if (jsonObject != null) {
				fileUploaderHelper.writeToResponse(jsonObject, response);
			}

		}
		// If exception, write it
		catch (Exception e) {
			exceptionCodeMappingHelper.processException(e, response);
		}

	}


	private void checkAuthorization(HttpServletRequest request, UploadServletAction actionByParameterName)
			throws MissingParameterException, AuthorizationException {

		// check authorization
		// if its not get progress (because we do not really care about authorization for get
		// progress and it uses an array of file ids)
		if (!actionByParameterName.equals(UploadServletAction.getProgress)) {

			// extract uuid
			final String fileIdFieldValue = fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId, false);

			// if this is init, the identifier is the one in parameter
			UUID clientOrJobId;
			String parameter = fileUploaderHelper.getParameterValue(request, UploadServletParameter.clientId, false);
			if (actionByParameterName.equals(UploadServletAction.getConfig) && parameter != null) {
				clientOrJobId = UUID.fromString(parameter);
			}
			// if not, get it from manager
			else {
				clientOrJobId = staticStateIdentifierManager.getIdentifier();
			}

			
			// call authorizer
			authorizer.getAuthorization(
					request,
					actionByParameterName,
					clientOrJobId,
					fileIdFieldValue != null ? getFileIdsFromString(fileIdFieldValue).toArray(new UUID[] {}) : null);

		}
	}


	private Serializable processAction(UploadServletAction actionByParameterName, HttpServletRequest request)
			throws Exception {
		log.debug("Processing action " + actionByParameterName.name());

		Serializable returnObject = null;
		switch (actionByParameterName) {
			case getConfig:
				String parameterValue = fileUploaderHelper.getParameterValue(request, UploadServletParameter.clientId, false);
				returnObject =
						uploadProcessor.getConfig(
								parameterValue != null ? UUID.fromString(parameterValue) : null);
				break;
			case verifyCrcOfUncheckedPart:
				returnObject = verifyCrcOfUncheckedPart(request);
				break;
			case prepareUpload:
				returnObject = prepareUpload(request);
				break;
			case clearFile:
				uploadProcessor.clearFile(UUID.fromString(fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId)));
				break;
			case clearAll:
				uploadProcessor.clearAll();
				break;
			case pauseFile:
				List<UUID> uuids = getFileIdsFromString(fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId));
				uploadProcessor.pauseFile(uuids);
				break;
			case resumeFile:
				returnObject =
						uploadProcessor.resumeFile(UUID.fromString(fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId)));
				break;
			case setRate:
				uploadProcessor.setUploadRate(UUID.fromString(fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId)),
						Long.valueOf(fileUploaderHelper.getParameterValue(request, UploadServletParameter.rate)));
				break;
			case getProgress:
				returnObject = getProgress(request);
				break;
		}
		return returnObject;
	}


	List<UUID> getFileIdsFromString(String fileIds) {
		String[] splittedFileIds = fileIds.split(",");
		List<UUID> uuids = Lists.newArrayList();
		for (int i = 0; i < splittedFileIds.length; i++) {
			uuids.add(UUID.fromString(splittedFileIds[i]));
		} 
		return uuids;
	}


	private Serializable getProgress(HttpServletRequest request)
			throws MissingParameterException {
		Serializable returnObject;
		String[] ids =
				new Gson()
						.fromJson(fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId), String[].class);
		Collection<UUID> uuids = Collections2.transform(Arrays.asList(ids), new Function<String, UUID>() {

			@Override
			public UUID apply(String input) {
				return UUID.fromString(input);
			}

		});
		returnObject = Maps.newHashMap();
		for (UUID fileId : uuids) {
			try {
				ProgressJson progress = uploadProcessor.getProgress(fileId);
				((HashMap<String, ProgressJson>) returnObject).put(fileId.toString(), progress);
			}
			catch (FileNotFoundException e) {
				log.debug("No progress will be retrieved for " + fileId + " because " + e.getMessage());
			}
		}
		return returnObject;
	}


	private Serializable prepareUpload(HttpServletRequest request)
			throws MissingParameterException, IOException {

		// extract file information
		PrepareUploadJson[] fromJson =
				new Gson()
						.fromJson(fileUploaderHelper.getParameterValue(request, UploadServletParameter.newFiles), PrepareUploadJson[].class);

		// prepare them
		final HashMap<String, UUID> prepareUpload = uploadProcessor.prepareUpload(fromJson);

		// return them
		return Maps.newHashMap(Maps.transformValues(prepareUpload, new Function<UUID, String>() {

			public String apply(UUID input) {
				return input.toString();
			};
		}));
	}


	private Boolean verifyCrcOfUncheckedPart(HttpServletRequest request)
			throws IOException, MissingParameterException, FileCorruptedException, FileStillProcessingException {
		UUID fileId = UUID.fromString(fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId));
		try {
			uploadProcessor.verifyCrcOfUncheckedPart(fileId,
					fileUploaderHelper.getParameterValue(request, UploadServletParameter.crc));
		}
		catch (InvalidCrcException e) {
			// no need to log this exception, a fallback behaviour is defined in the
			// throwing method.
			// but we need to return something!
			return Boolean.FALSE;
		}
		return Boolean.TRUE;
	}
}
 

非同步上傳UploadServletAsync

@Component("javaLargeFileUploaderAsyncServlet")
@WebServlet(name = "javaLargeFileUploaderAsyncServlet", urlPatterns = { "/javaLargeFileUploaderAsyncServlet" }, asyncSupported = true)
public class UploadServletAsync extends HttpRequestHandlerServlet
		implements HttpRequestHandler {

	private static final Logger log = LoggerFactory.getLogger(UploadServletAsync.class);

	@Autowired
	ExceptionCodeMappingHelper exceptionCodeMappingHelper;

	@Autowired
	UploadServletAsyncProcessor uploadServletAsyncProcessor;
	
	@Autowired
	StaticStateIdentifierManager staticStateIdentifierManager;

	@Autowired
	StaticStateManager<StaticStatePersistedOnFileSystemEntity> staticStateManager;

	@Autowired
	FileUploaderHelper fileUploaderHelper;

	@Autowired
	Authorizer authorizer;

	/**
	 * Maximum time that a streaming request can take.<br>
	 */
	private long taskTimeOut = DateUtils.MILLIS_PER_HOUR;


	@Override
	public void handleRequest(final HttpServletRequest request, final HttpServletResponse response)
			throws ServletException, IOException {

		// process the request
		try {

			//check if uploads are allowed
			if (!uploadServletAsyncProcessor.isEnabled()) {
				throw new UploadIsCurrentlyDisabled();
			}
			
			// extract stuff from request
			final FileUploadConfiguration process = fileUploaderHelper.extractFileUploadConfiguration(request);

			log.debug("received upload request with config: "+process);

			// verify authorization
			final UUID clientId = staticStateIdentifierManager.getIdentifier();
			authorizer.getAuthorization(request, UploadServletAction.upload, clientId, process.getFileId());

			//check if that file is not paused
			if (uploadServletAsyncProcessor.isFilePaused(process.getFileId())) {
				log.debug("file "+process.getFileId()+" is paused, ignoring async request.");
				return;
			}
			
			// get the model
			StaticFileState fileState = staticStateManager.getEntityIfPresent().getFileStates().get(process.getFileId());
			if (fileState == null) {
				throw new FileNotFoundException("File with id " + process.getFileId() + " not found");
			}

			// process the request asynchronously
			final AsyncContext asyncContext = request.startAsync();
			asyncContext.setTimeout(taskTimeOut);


			// add a listener to clear bucket and close inputstream when process is complete or
			// with
			// error
			asyncContext.addListener(new UploadServletAsyncListenerAdapter(process.getFileId()) {

				@Override
				void clean() {
					log.debug("request " + request + " completed.");
					// we do not need to clear the inputstream here.
					// and tell processor to clean its shit!
					uploadServletAsyncProcessor.clean(clientId, process.getFileId());
				}
			});

			// then process
			uploadServletAsyncProcessor.process(fileState, process.getFileId(), process.getCrc(), process.getInputStream(),
					new WriteChunkCompletionListener() {

						@Override
						public void success() {
							asyncContext.complete();
						}


						@Override
						public void error(Exception exception) {
							// handles a stream ended unexpectedly , it just means the user has
							// stopped the
							// stream
							if (exception.getMessage() != null) {
								if (exception.getMessage().equals("Stream ended unexpectedly")) {
									log.warn("User has stopped streaming for file " + process.getFileId());
								}
								else if (exception.getMessage().equals("User cancellation")) {
									log.warn("User has cancelled streaming for file id " + process.getFileId());
									// do nothing
								}
								else {
									exceptionCodeMappingHelper.processException(exception, response);
								}
							}
							else {
								exceptionCodeMappingHelper.processException(exception, response);
							}

							asyncContext.complete();
						}

					});
		}
		catch (Exception e) {
			exceptionCodeMappingHelper.processException(e, response);
		}

	}

}
 

3，請求流程圖：