Re: PDFSignature NullPointerException

ok, it turned out to be a problem with our custom ResourceResolver...
...returning null in getOutputStream(...) wasn't a good idea. 😎

Best regards,
DaveLaw

On 17/03/2026 12:50, David Law wrote:
> Hi there,
>
> I'm trying to create a signed PDF with FOP v2.11 & JDK 17.
>
> I am NOT using a Config file (i.e. fop.xconf).
>
> Instead I'm supplying an instance of PDFSignParams.
> -> FOP then internally creates an instance of PDFSignature.
> -> I've checked the PDFSignature instance is able to read the Keystore 
> & sign content.
>
> When creating the PDF from the FO, a *NullPointerException* is raised.
> The only Method invoked on PDFSignature is add(final PDFPage page).
>
> The message is:
> Cannot invoke "java.io.OutputStream.write(byte[], int, int)" because 
> "this.out" is null
>
> (I did something similar for encryption with an instance of 
> PDFEncryptionParams. That worked fine)
>
> Before I take time to create a detailed example,
> I thought I'd ask if anyone has had the same problem.
>
> The generatePDFfromFO Method looks like this:
>
> private static byte[] generatePDFfromFO(final byte[] bytesFO, final 
> TransformerFactory factory) throws Exception {
>
>     final     var foUserAgent   = FOP_FACTORY.newFOUserAgent();
>     ;             foUserAgent.setProducer("ap FOP");
>     ;             foUserAgent.setCreationDate(new Date());
>     ;             foUserAgent.setTargetResolution(300 /* dpi */);
>
>     final     var foSignParms   = new 
> PDFSignParams("path/fopTest.pkcs12", null, null, null, "fopTest");
>
>     @SuppressWarnings("unchecked")
>     final     var foRendOpt     = (Map<Object, Object>) 
> foUserAgent.getRendererOptions();
>     ;             foRendOpt.put("sign-params", foSignParms);
>
>     final     var pdfBytesSizeGuess  = bytesFO.length / 2;
>     final     var pdfBytesBaos       = new 
> ByteArrayOutputStream(pdfBytesSizeGuess);
>
>     try          (pdfBytesBaos)
>     {
>         final var fop                = 
> foUserAgent.newFop(MimeConstants.MIME_PDF, pdfBytesBaos);
>         final var saxResult          = new 
> SAXResult(fop.getDefaultHandler());
>
>         final var xmlSource          = getSource(bytesFO);
>
>         final var transformer        = factory.newTransformer();
>         ;         transformer.transform(xmlSource, saxResult); // -> 
> *NullPointerException*
>     }
>     return        pdfBytesBaos.toByteArray();
> }
>
> Any ideas, anyone?
>
> Thanks in advance,
> DaveLaw