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 = 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;
}
}
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。
详细代码可以参照我写的这篇文章：http://t.cn/AiHwnJaB