Java 上传不适用于servlets 2.5

我已经创建了一个servlet 3.1 java应用程序，用户可以上传100MB以上的大文件并发布到Heroku free tier，但是由于文件大小的原因，它似乎被阻塞了

所以我将我的项目改为使用Servlet2.5规范，但是现在当使用upload.parseRequestrequest下面的代码时，上传文件的列表总是空的。为什么?

public class EncodingController extends HttpServlet {
    private static final long serialVersionUID = 1L;

    // location to store file uploaded
    private static final String UPLOAD_DIRECTORY = "upload";

    // upload settings
    private static final int MEMORY_THRESHOLD   = 1024 * 1024 * 200;  // 3MB
    private static final int MAX_FILE_SIZE      = 1024 * 1024 * 200; // 40MB
    private static final int MAX_REQUEST_SIZE   = 1024 * 1024 * 400; // 50MB

    /**
     * @see HttpServlet#HttpServlet()
     */
    public EncodingController() {
        super();
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // checks if the request actually contains upload file
        if (!ServletFileUpload.isMultipartContent(request)) {
            // if not, we stop here
            PrintWriter writer = response.getWriter();
            writer.println("Error: Form must has enctype=multipart/form-data.");
            writer.flush();
            return;
        }

        // configures upload settings
        DiskFileItemFactory factory = new DiskFileItemFactory();
        // sets memory threshold - beyond which files are stored in disk
        factory.setSizeThreshold(MEMORY_THRESHOLD);
        // sets temporary location to store files
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

        ServletFileUpload upload = new ServletFileUpload(factory);

        // sets maximum size of upload file
        upload.setFileSizeMax(MAX_FILE_SIZE);

        // sets maximum size of request (include file + form data)
        upload.setSizeMax(MAX_REQUEST_SIZE);

        // constructs the directory path to store upload file
        // this path is relative to application's directory
        String uploadPath = getServletContext().getRealPath("")
                + File.separator + UPLOAD_DIRECTORY;

        // creates the directory if it does not exist
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }

        try {
            // parses the request's content to extract file data
            @SuppressWarnings("unchecked")
            List<FileItem> formItems = upload.parseRequest(request);

            if (formItems != null && formItems.size() > 0) {
                // iterates over form's fields
                for (FileItem item : formItems) {
                    // processes only fields that are not form fields
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        String filePath = uploadPath + File.separator + fileName;
                        File storeFile = new File(filePath);

                        // saves the file on disk
                        item.write(storeFile);
                        request.setAttribute("message",
                            "Upload has been done successfully!");
                    }
                }
            }
        } catch (Exception ex) {
            request.setAttribute("message",
                    "There was an error: " + ex.getMessage());
        }
        // redirects client to message page
        getServletContext().getRequestDispatcher("/message.jsp").forward(
                request, response);
    }

---

使用以下代码解决问题：

protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        boolean isMultipart = ServletFileUpload.isMultipartContent(request);

        response.setContentType("application/json");
        PrintWriter out = response.getWriter();

        if (isMultipart) {
            FileItemFactory factory = new DiskFileItemFactory();
            ServletFileUpload upload = new ServletFileUpload(factory);

            try {
                List items = upload.parseRequest(request);
                Iterator iterator = items.iterator();
                while (iterator.hasNext()) {
                    FileItem item = (FileItem) iterator.next();
                    if (!item.isFormField()) {
                        String fileName = item.getName();

                        IUploader uploader = new S3Uploader();
                        String fileUrl = uploader.sendFile(item.getInputStream(), item.getSize());

                        if (!fileUrl.isEmpty()) {
                            IEncoder encoder = new Zencoder();

                            out.append("{ 'encodedFile':" + encoder.encode(fileUrl) + "}");

                            response.setStatus(HttpServletResponse.SC_OK);

                            return;
                        }
                    }
                }
            } catch (Exception e) {}

            response.setStatus(HttpServletResponse.SC_NO_CONTENT);

            out.append("{}");
        }

    }