中止从 servlet 上传以限制文件大小

问题描述

我想限制可以上传到应用程序的文件大小.为了实现这一点，我想在上传的文件大小超过限制时从服务器端中止上传过程.

I'd like to limit the size of the file that can be uploaded to an application. To achieve this, I'd like to abort the upload process from the server side when the size of the file being uploaded exceeds a limit.

有没有办法在不等待 HTTP 请求完成的情况下从服务器端中止上传过程?

Is there a way to abort an upload process from the server side without waiting the HTTP request to finish?

推荐答案

你可以这样做(使用 Commons 库):

You can do something like this (using the Commons library):

    public class UploadFileServiceImpl extends HttpServlet
    {
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException
        {
            response.setContentType("text/plain");

            try
            {
                FileItem uploadItem = getFileItem(request);
                if (uploadItem == null)
                {
                        // ERROR
                }   

                // Add logic here
            }
            catch (Exception ex)
            {
                response.getWriter().write("Error: file upload failure: " + ex.getMessage());           
            }
        }

        private FileItem getFileItem(HttpServletRequest request) throws FileUploadException
        {
            DiskFileItemFactory factory = new DiskFileItemFactory();        

             // Add here your own limit         
             factory.setSizeThreshold(DiskFileItemFactory.DEFAULT_SIZE_THRESHOLD);

         ServletFileUpload upload = new ServletFileUpload(factory);

             // Add here your own limit
             upload.setSizeMax(DiskFileItemFactory.DEFAULT_SIZE_THRESHOLD);


            List<?> items = upload.parseRequest(request);
            Iterator<?> it = items.iterator();
            while (it.hasNext())
            {
                FileItem item = (FileItem) it.next();
                        // Search here for file item
                if (!item.isFormField() && 
                  // Check field name to get to file item  ... 
                {
                    return item;
                }
            }

            return null;
        }
    }

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