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
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@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;
}
}
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异步上传UploadServletAsync
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@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);
}
}
}
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3，请求流程图：
主要思路就是将文件切分，然后分块上传。
