SQL & PL/SQL

Hi,
Using UTL_HTTP Iam trying to contact a servlet which uses the input XML and XSL/FO to produce a PDF.However, when I run the procedure , I get the following error 'File does not begin with -%PDF' ? I checked the output on the console and the blob values does not start with %PDF . Below is the sample from my code , please let me know if Iam commiting a mistake somewhere. I confirmed that the servlet itself is working fine by confirming with test webpage that takes xml and stylesheet input and generates a PDF when 'submitted' to servlet on the click of a button.

INSERT INTO TESTPDF ( PDF_REPORT ) VALUES ( Empty_Blob() ) RETURNING PDF_REPORT INTO vBlobRef;
vReportURL :='/rufop/fop?xml='||xmldoc||'&xsltRPath=../../test/PAXSL.xsl';
req := UTL_HTTP.BEGIN_REQUEST (url=>vReportURL, method=>'POST');
resp := utl_http.get_response(req);
loop
begin
Utl_Http.read_raw(resp, vData);
Dbms_Lob.writeAppend ( lob_loc => vBlobRef , amount => Utl_Raw.length(vData) , buffer => vData );
exception
when utl_http.end_of_body then
exit;
end;
end loop;

Utl_Http.end_response(resp);
owa_util.mime_header('application/pdf',false);
htp.p('Content-Disposition: inline; filename="test.pdf"');
htp.p('Content-Length: '|| dbms_lob.getlength(vBlobRef));
owa_util.http_header_close;
wpg_docload.download_file(vBlobRef);

Thanks in advance,
Jen