add custom value for signature file using pdfbox java

Question

How i will add my custom value as like (xyz123) when adding signature.Because when i adding signature that time i am not able to add custom file for signature. the field "signature1" automatically added inside the document. My output file screenshot attached bello:

Instead of "signature1", I want to add my custom value as (xyz123)

            throws IOException {
        PDSignature pdSignature = new PDSignature();
        pdSignature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);
        pdSignature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);
        pdSignature.setName("jvmfy");
        pdSignature.setReason("Learn how to sign pdf with jvmfy.com!");
        pdSignature.setLocation("location");

        // the signing date, needed for valid signature
        pdSignature.setSignDate(Calendar.getInstance());

        // register signature dictionary and sign interface
        document.addSignature(pdSignature, signature);

        // write incremental (only for signing purpose)
        // use saveIncremental to add signature, using plain save method may break up a
        // document
        document.saveIncremental(output);
    }

private void signDetached(SignatureInterface signature, PDDocument document, OutputStream output)
            throws IOException {
        PDSignature pdSignature = new PDSignature();
        pdSignature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);
        pdSignature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);
        
        pdSignature.setSignDate(Calendar.getInstance());
        PDAcroForm acroForm = document.getDocumentCatalog().getAcroForm();
        if (acroForm == null)
        {
            acroForm = new PDAcroForm(document);
            document.getDocumentCatalog().setAcroForm(acroForm);
        }
        PDSignatureField signatureField = new PDSignatureField(acroForm);
        signatureField.setPartialName("xyz123");
        signatureField.setValue(pdSignature);
        signatureField.getWidgets().get(0).setPage(document.getPage(0));
        document.addSignature(pdSignature, signature);
        document.saveIncremental(output);
    }```

question from:https://stackoverflow.com/questions/65878933/add-custom-value-for-signature-file-using-pdfbox-java

Answer 1

You need your PDSignatureField object... when you have it, do this:

signatureField.setPartialName("xyz123");

If the code doesn't create its own PDSignatureField object (as in the example for invisible signature fields), PDFBox does it for you. You can get all PDSignatureField objects by calling PDDocument.getSignatureFields().

If you created the file yourself, then there is only one such field. If you are signing existing files, then it's more tricky, then I'd recommend that you compare the field names or the results of getCOSObject() (i.e. create two sets). Don't assume that the last one is the right one (in some cases it isn't).

Or you create the field yourself:

PDAcroForm acroForm = document.getDocumentCatalog().getAcroForm(null);
if (acroForm == null)
{
    acroForm = new PDAcroForm(document);
    document.getDocumentCatalog().setAcroForm(acroForm);
}
PDSignatureField signatureField = new PDSignatureField(acroForm);
signatureField.setValue(signature);
signatureField.getWidgets().get(0).setPage(document.getPage(0));
acroForm.getFields().add(signatureField);
// page annotation, only needed if PDF/A
document.getPage(0).getAnnotations().add(signatureField.getWidgets().get(0));
document.getPage(0).getCOSObject().setNeedToBeUpdated(true);