Java大文件上传详解及实例代码

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://blog.ncmem.com/wordpress/2019/08/12/java-http%E5%A4%A7%E6%96%87%E4%BB%B6%E6%96%AD%E7%82%B9%E7%BB%AD%E4%BC%A0%E4%B8%8A%E4%BC%A0/