a text/xml declaration may occur only at the very beginning of input in word while using POI

I am creating an word document using Apache POI when i am running my code as a main program it is running fine and creating the word document with the header footer but when i am trying to add it in my web application then it is showing error that,a text/xml declaration may occur only at the very beginning of the document.I am using POI 3.10 jar.Here is my code i am posting

    XWPFDocument document = new XWPFDocument();

    CTP ctp = CTP.Factory.newInstance();
    CTR ctr = ctp.addNewR();
    CTRPr rpr = ctr.addNewRPr();
    CTText footerText = ctr.addNewT();

    //writing Footer Text for each page 
    footerText.setStringValue("Client Service Contact:Tomas.Layrisse@mshgroupconsulting.com                           990765432");

    XWPFParagraph footerParagraph = new XWPFParagraph(ctp, document);
    XWPFParagraph[] setfooterTexts = new XWPFParagraph[1];

    setfooterTexts[0]=footerParagraph;

    CTSectPr sectPr = document.getDocument().getBody().addNewSectPr();
    XWPFHeaderFooterPolicy headerFooterPolicy = new XWPFHeaderFooterPolicy(document, sectPr);

    //setting footer to each page

    headerFooterPolicy.createFooter(XWPFHeaderFooterPolicy.DEFAULT, setfooterTexts);

    String contentType="application/msword";
        response.addHeader("Content-Disposition", "attachment; filename=\""+ "reportName" + ".docx\"");
        response.setContentType(contentType);
        ServletOutputStream out = response.getOutputStream();           
        document.write(out);

somebody please help me ..