Returning a PDF file from a Java Bean to a JSP

Question

EDIT: See my working code in the answers below.

---

In brief: I have a JSP file which calls a method in a Java Bean. This method creates a PDF file and in theory, returns it to the JSP so that the user can download it. However, upon loading the PDF, Adobe Reader gives the error: File does not begin with '%PDF-'.

In detail: So far, the JSP successfully calls the method, the PDF is created and then the JSP appears to give the user the finished PDF file. However, as soon as Adobe Reader tries to open the PDF file, it gives an error: File does not begin with '%PDF-'. Just for good measure, I have the method create the PDF on my Desktop so that I can check it; when I open it normally within Windows is appears fine. So why is the output from the JSP different?

To create the PDF, I'm using Apache FOP. I'm following one of their most basic examples, with the exception of passing the resulting PDF to a JSP instead of simply saving it to the local machine. I have been following their basic usage pattern and this example code.

Here's my JSP file:

<%@ taglib uri="utilTLD" prefix="util" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>
<%@ page language="java" session="false" %>
<%@ page contentType="application/pdf" %>

<%-- Construct and initialise the PrintReportsBean --%>
<jsp:useBean id="printReportsBean" scope="request" class="some.package.printreports.PrintReportsBean" />
<jsp:setProperty name="printReportsBean" property="*"/>

<c:set scope="page" var="xml" value="${printReportsBean.download}"/>

Here's my Java Bean method:

//earlier in the class...
private static FopFactory fopFactory = FopFactory.newInstance();

public File getDownload() throws UtilException {

    OutputStream out = null;
    File pdf = new File("C:\\documents and settings\\me\\Desktop\\HelloWorld.pdf");
    File fo  = new File("C:\\somedirectory", "HelloWorld.fo");

    try {

        FOUserAgent foUserAgent = fopFactory.newFOUserAgent();

        out = new FileOutputStream(pdf);
        out = new BufferedOutputStream(out);

        Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, foUserAgent, out);

        TransformerFactory factory = TransformerFactory.newInstance();
        Transformer transformer = factory.newTransformer(); //identity transformer

        Source src = new StreamSource(fo);

        Result res = new SAXResult(fop.getDefaultHandler());

        transformer.transform(src, res);

        return pdf;

    } catch (Exception e) {

         throw new UtilException("Could not get download. Msg = "+e.getMessage());

    } finally {

         try {
             out.close();
         } catch (IOException io) {
             throw new UtilException("Could not close OutputStream. Msg = "+io.getMessage());
         }
    }
}

I realise that this is a very specific problem, but any help would be much appreciated!

Answer 1

Just a guess, but have you checked the MIME type that your JSP page is returning?

edit: if I actually read the code you posted I would see you did set it, so nevermind :)

edit2: Aren't the newlines between JSP tags in your JSP code going to end up in the output stream? Could that throw off the response returned by the server? I don't know anything about the format of a PDF, but does it depend on certain "marker" characters being in certain locations in the file? (The error message returned sounds like it does).

Answer 2

The way I have implemented this type of feature in the past is to make a servlet write the contents of the PDF file out to the response as a stream. I don't have the source code with me any longer (and it's been at least a year since I did any servlet/jsp work), but here is what you might want to try:

In a servlet, get a handle on the response's output stream. Change the mime type of the response to "application/pdf", and have the servlet do the file handling you have in your example. Only, instead of returning the File object, have the servlet write the file to the output stream. See examples of file i/o and just replace any outfile.write(...) lines with responseStream.write(...) and you should be set to go. Once you flush and close the output stream, and do the return, if I remember correctly, the browser should be able to pick up the pdf from the response.

Answer 3

I agree with matt b, maybe its the spaces between JSP tags. Try putting the directive

<%@ page trimDirectiveWhitespaces="true" %>

Answer 4

Ok, I got this working. Here's how I did it:

JSP:

<%@ taglib uri="utilTLD" prefix="util" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>
<%@ page language="java" session="false" %>
<%@ page contentType="application/pdf" %>

<%-- Construct and initialise the PrintReportsBean --%>
<jsp:useBean id="printReportsBean" scope="request" class="some.package.PrintReportsBean" />
<jsp:setProperty name="printReportsBean" property="*"/>

<%
    // get report format as input parameter  
    ServletOutputStream servletOutputStream = response.getOutputStream();

    // reset buffer to remove any initial spaces
    response.resetBuffer(); 

    response.setHeader("Content-disposition", "attachment; filename=HelloWorld.pdf");

    // check that user is authorised to download product
    printReportsBean.getDownload(servletOutputStream);
%>

Java Bean method:

//earlier in the class...
private static FopFactory fopFactory = FopFactory.newInstance();

public void getDownload(ServletOutputStream servletOutputStream) throws UtilException {

    OutputStream outputStream = null;

    File fo  = new File("C:\\some\\path", "HelloWorld.fo");

    try {

        FOUserAgent foUserAgent = fopFactory.newFOUserAgent();

        outputStream = new BufferedOutputStream(servletOutputStream);

        Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, foUserAgent, outputStream);

        TransformerFactory factory = TransformerFactory.newInstance();
        Transformer transformer = factory.newTransformer(); //identity transformer

        Source src = new StreamSource(fo);

        Result res = new SAXResult(fop.getDefaultHandler());

        transformer.transform(src, res);

    } catch (Exception e) {

        throw new UtilException("Could not get download. Msg = "+e.getMessage());

    } finally {

        try {
            outputStream.close();
        } catch (IOException io) {
            throw new UtilException("Could not close OutputStream. Msg = "+io.getMessage());
        }
     }
 }

Thanks to everyone for their input!