FDF header signature not found

hello,

 

With submitting PDF forms from a web browser, I sporadically have the following error:

Caused by: java.io.IOException: FDF header signature not found.
 at com.lowagie.text.pdf.PRTokeniser.checkFdfHeader(Unknown Source)
 at com.lowagie.text.pdf.FdfReader.readPdf(Unknown Source)
 at com.lowagie.text.pdf.PdfReader.<init>(Unknown Source)
 at com.lowagie.text.pdf.PdfReader.<init>(Unknown Source)
 at com.lowagie.text.pdf.FdfReader.<init>(Unknown Source)
 at ch.abacus.flow.lib.AbaWorkflow.submitPDFForm(AbaWorkflow.java:246)

 

It is difficult to reproduce, sometime (most time) it works, but sometimes it fails. In the browser, the form looks fine, the fields can be edited. Something must happen on the post.  If it fails, I can press the back button and submit again —--- and then it works.

 

In treating the post I do something like this:

 

        ByteArrayOutputStream baos = new ByteArrayOutputStream();

 

        byte[] buf=new byte[100*1024];
        InputStream is = request.getInputStream();
        while (is.read(buf) !=-1) {
          baos.write(buf);
        }

 

        try {
            wf.submitPDFForm(wfId, sid, baos.toByteArray());

           ....

 

I have no clue, what causes this error and would be glad if somebody helped me out.

 

Thank you

Regards

Hubert