Question

I have a file uploader on my website, since i cannot use php I’m using jsp pages.
My main page uses a hidden iframe to post data to a second jsp page that handles the upload. However the uploaded images is always corrupted, more specifically it’s larger in size than the original file.
Any hints or tips would be appreciated.
Main page code:

<form id="uploadForm">
    <input type="file" name="datafile" /></br>
    <input type="button" value="upload" onClick="fileUpload(document.getElementById('uploadForm'),'single_upload_page.jsp','upload'); return false;" >
</form>

The code for fileUpload concerning the form:

form.setAttribute("target","upload_iframe");
form.setAttribute("action", action_url);
form.setAttribute("method","post");
form.setAttribute("enctype","multipart/form-data");
form.setAttribute("encoding","multipart/form-data");

// Submit the form...
form.submit();

The code that handles the upload:

DataInputStream in = new DataInputStream(request.getInputStream());
int dataLength = request.getContentLength();

Because of the varying size of dataLength I’m assuming that the request.getInputStream receives extra data.

I only posted the code I think matters, if I need to post more or if you need any more information don’t hesitate to ask.

Answer 1

Simple request

The problem is request.getContentLength() gives the length of the whole request, containing headers and all.

You have to search for Content-Length header value, convert it to Long and that’s the proper size.

if you can’t get it (it can be unavailable) simply consume the whole input stream. But of course, you’ll not have idea of the file size.

Multipart request

Anyway… as your form is multipart/form-data you should use some library to parse all the different parts, find the one you need (the file part) and read it. You can use commons-fileupload.

Sample from real life

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse resp)
        throws ServletException, IOException 
{
        // (....)
        FileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload sfu = new ServletFileUpload(factory);
        FileItemIterator it = sfu.getItemIterator(request);
        // TAKE THE FIRST PART FROM REQUEST (HERE COMES THE FILE)
        if (it.hasNext())
        {
            FileItemStream fis = it.next();
            // grab data from fis (content type, name)
            ...fis.getContentType()...
            ...fis.getName()...
            // GET CONTENT LENGTH SEARCH FOR THE LENGTH HEADER
            ...getContentLength(fis.getHeaders(), request)...
            // here I use an own method to process data
            // but FileItemStream has an openStream method
            FileItem item = processUpload(factory, fis, uploadInfo);
            (....)
        }



private long getContentLength(FileItemHeaders pHeaders, HttpServletRequest request)
{
    try
    {
        return Long.parseLong(pHeaders.getHeader("Content-length"));
    }
    catch (Exception e)
    {
                    // if I can't grab the value return an approximate (in my case I don't care)
        return request.getContentLength();
    }
}