我想限制应用程序上传的文件大小。为了达到这个目的,当上传的文件大小超过限制时,我希望能够从服务器端终止上传过程。是否有一种方法可以在不等待HTTP请求完成的情况下从服务器端中止上传过程?
使用JavaEE 6 / Servlet 3.0,做这件事的首选方法是在您的servlet上使用@MultipartConfig注释,如下所示:
@MultipartConfig(location="/tmp", fileSizeThreshold=1024*1024,
maxFileSize=1024*1024*5, maxRequestSize=1024*1024*5*5)
public class UploadFileServiceImpl extends HttpServlet ...
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;
}
}
multi = new MultipartRequest(request, dirName, FILE_SIZE_LIMIT);
if(submitButton.equals(multi.getParameter("Submit")))
{
out.println("Files:");
Enumeration files = multi.getFileNames();
while (files.hasMoreElements()) {
String name = (String)files.nextElement();
String filename = multi.getFilesystemName(name);
String type = multi.getContentType(name);
File f = multi.getFile(name);
if (f.length() > FILE_SIZE_LIMIT)
{
//show error message or
//return;
return;
}
}
这样你就不必等待完全处理你的HttpRequest,可以立即返回或向客户端显示错误消息。希望对你有所帮助。
curl --request POST --data-binary @path/to/big.zip http://localhost:8080/endpoint
。 - Giszmo