因为需要研究下断点上传的问题。找了很久终于找到一个对照好的项目。

在GoogleCode上面，代码弄下来超级未便利，还是配置hosts才好，把代码从头上传到了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要领实现了http的断点上传。

因为html5 里面有读取文件支解文件的类库，所以才可以撑持断点上传，所以这个只能在html5 撑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，监听等要领。

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