iText Fill Form / Copy Page to new Document

Question

I'm useing iText to fill a template PDF which contains a AcroForm. Now I want to use this template to create a new PDF with dynamically pages. My idea is it to fill the template PDF, copy the page with the written fields and add it to a new file. They main Problem is that our customer want to designe the template by them self. So I'm not sure if I try the right way to solve this Problem.

So I've created this code which don't work right now I get the error com.itextpdf.io.IOException: PDF header not found.

My Code

 x = 1;
try (PdfDocument finalDoc = new PdfDocument(new PdfWriter("C:\\Users\\...Final.pdf"))) {
        for (HashMap<String, String> map : testValues) {
            String path1 = "C:\\Users\\.....Temp.pdf"
            InputStream template = templateValues.get("Template");

            PdfWriter writer = new PdfWriter(path1);

            try (PdfDocument pdfDoc = new PdfDocument(new PdfReader(template), writer)) {
                PdfAcroForm form = PdfAcroForm.getAcroForm(pdfDoc, true);
                for (HashMap.Entry<String, String> map2 : map.entrySet()) {

                    if (form.getField(map2.getKey()) != null) {
                        Map<String, PdfFormField> fields = form.getFormFields();
                        fields.get(map2.getKey()).setValue(map2.getValue());


                    }

                }
            } catch (IOException | PdfException ex) {
                System.err.println("Ex2: " + ex.getMessage());

            }
            if (x != 0 && (x % 5) == 0) {
                try (PdfDocument tempDoc = new PdfDocument(new PdfReader(path1))) {
                    PdfPage page = tempDoc.getFirstPage();
                    finalDoc.addPage(page.copyTo(finalDoc));

                } catch (IOException | PdfException ex) {
                    System.err.println("Ex3: " + ex.getMessage());

                }

            }
             x++;
       }
    } catch (IOException | PdfException ex) {
        System.err.println("Ex: " + ex.getMessage());
    }

Answer 1

Part 1 - PDF Header is Missing

this appears to be caused by you attempting to re-read an InputStream w/in a loop that has already been read (and, depending on the configuration of the PdfReader, closed). Solving for this depends on the specific type of InputStream being used - if you want to leave it as a simple InputStream (vs. a more specific yet more capable InputStream type) then you'll need to first slurp up the bytes from the stream into memory (e.g. a ByteArrayOutputStream) then create your PDFReaders based on those bytes.

i.e.

ByteArrayOutputStream templateBuffer = new ByteArrayOutputStream();
while ((int c = template.read()) > 0) templateBuffer.write(c);
for (/* your loop */) {
    ...
    PdfDocument filledInAcroFormTemplate = new PdfDocument(new PdfReader(new ByteArrayInputStream(templateBuffer.toByteArray())), new PdfWriter(tmp))
   ...

Part 2 - other problems

Couple of things

1. make sure to grab the recently released 7.0.1 version of iText since it included a couple of fixes wrt/ AcroForm handling
2. you can probably get away with using ByteArrayOutputStreams for your temporary PDFs (vs. writing them out to files) - i'll use this approach in the example below
3. PdfDocument/PdfPage is in the "kernel" module, yet AcroForms are in the "form" module (meaning PdfPage is intentionally unaware of AcroForms) - IPdfPageExtraCopier is sortof the bridge between the modules. In order to properly copy AcroForms, you need to use the two-arg copyTo() version, passing an instance of PdfPageFormCopier

4. field names must be unique in the document (the "absolute" field name that is - i'll skip field hierarcies for now). Since we're looping through and adding the fields from the template multiple times, we need to come up with a strategy to rename the fields to ensure uniqueness (the current API is actually a little bit clunky in this area)

   File acroFormTemplate = new File("someTemplate.pdf");
   Map<String, String> someMapOfFieldToValues = new HashMap<>();
   try (
       PdfDocument  finalOutput = new PdfDocument(new PdfWriter(new FileOutputStream(new File("finalOutput.pdf")));
   ) {
       for (/* some looping condition */int x = 0; x < 5; x++) {
           // for each iteration of the loop, create a temporary in-memory
           // PDF to handle form field edits.
           ByteArrayOutputStream tmp = new ByteArrayOutputStream();
           try (
               PdfDocument filledInAcroFormTemplate = new PdfDocument(new PdfReader(new FileInputStream(acroFormTemplate)), new PdfWriter(tmp));
           ) {
               PdfAcroForm acroForm = PdfAcroForm.getAcroForm(filledInAcroFormTemplate, true);
               for (PdfFormField field : acroForm.getFormFields().values()) {
                   if (someMapOfFieldToValues.containsKey(field.getFieldName())) {
                       field.setValue(someMapOfFieldToValues.get(field.getFieldName()));
                   }
               }
               // NOTE that because we're adding the template multiple times
               // we need to adopt a field renaming strategy to ensure field
               // uniqueness in the final document.  For demonstration's sake
               // we'll just rename them prefixed w/ our loop counter
               List<String> fieldNames = new ArrayList<>();
               fieldNames.addAll(acroForm.getFormFields().keySet()); // avoid ConfurrentModification
               for (String fieldName : fieldNames) {
                   acroForm.renameField(fieldName, x+"_"+fieldName);
               }
           }
   
           // the temp PDF needs to be "closed" for all the PDF finalization
           // magic to happen...so open up new read-only version to act as
           // the source for the merging from our in-memory bucket-o-bytes
           try (
               PdfDocument readOnlyFilledInAcroFormTemplate = new PdfDocument(new PdfReader(new ByteArrayInputStream(tmp.toByteArray())));
           ) {
               // although PdfPage.copyTo will probably work for simple pages, PdfDocument.copyPagesTo
               // is a more comprehensive copy (wider support for copying Outlines and Tagged content)
               // so it's more suitable for general page-copy use.  Also, since we're copying AcroForm
               // content, we need to use the PdfPageFormCopier
               readOnlyFilledInAcroFormTemplate.copyPagesTo(1, 1, finalOutput, new PdfPageFormCopier());
           }
       }
   }
   

Answer 2

Close your PdfDocuments when you are done with adding content to them.