1，项目调研

因为需要研究下断点上传的问题。找了很久终于找到一个比较好的项目。

在GoogleCode上面，代码弄下来超级不方便，还是配置hosts才好，把代码重新上传到了github上面。

https://github.com/freewebsys/java-large-file-uploader-demo

效果：

上传中，显示进度，时间，百分比。

点击【Pause】暂停，点击【Resume】继续。

2，代码分析

原始项目：

https://code.google.com/p/java-large-file-uploader/

这个项目最后更新的时间是 2012 年，项目进行了封装使用最简单的方法实现了http的断点上传。

因为html5 里面有读取文件分割文件的类库，所以才可以支持断点上传，所以这个只能在html5 支持的浏览器上面展示。

同时，在js 和 java 同时使用 cr32 进行文件块的校验，保证数据上传正确。

代码在使用了最新的servlet 3.0 的api，使用了异步执行，监听等方法。

上传类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 = http://www.mamicode.com/fileUploaderHelper.getParameterValue(request, UploadServletParameter.fileId, false);>
异步上传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，请求流程图：

主要思路就是将文件切分，然后分块上传。





java http大文件上传，断点续传项目研究，Github上传源代码