PDFBox - Refreshing nested PDComboBox from Java

I'm new using PDFBox and need some help.

I have searched on the internet, but I didn't find anything and have tried plenty of things.

I have to parse from a PDF file in order to fill out some fields from Java and export it filled out again, taking data from the database. I have several nested combo boxes and when I put the value in the first one, it shows the correct text for the value, but the problem arrives when I put the value in the nested combo box, it shows the value instead of the text, it doesn't refresh the value's list depend on the first combo box.

This problem doesn't happen if you edit the PDF file from a PDF editor.

public ByteArrayOutputStream parseToSmartPdf(final File file, final Map<String, String> pdfContentMap) {
    final ByteArrayOutputStream baos;
    try {
        final InputStream inputStream = new BufferedInputStream(new FileInputStream(file));
        final PDDocument pdfDocument = PDDocument.load(inputStream.readAllBytes());
        inputStream.close();
        final PDAcroForm pdfAcroForm = pdfDocument.getDocumentCatalog().getAcroForm();
        if (Objects.isNull(pdfAcroForm)) {
            throw new FileEmptyException();
        }

        for (final Map.Entry<String, String> entry : new TreeMap<>(pdfContentMap).entrySet()) {
            final String key = entry.getKey();
            final String value = entry.getValue();
            final PDField field = pdfAcroForm.getField(key);
            if ("Tx".equals(field.getFieldType())) {
                field.setValue(value);
            } else if ("Ch".equals(field.getFieldType())) {
                if (field instanceof PDComboBox) {
                    final PDComboBox pdComboBox = (PDComboBox) field;
                    pdComboBox.setValue(value);
                }
            }
        }
        baos = new ByteArrayOutputStream();
        pdfDocument.save(baos);
        pdfDocument.close();
    } catch (final IOException e) {
        throw new FileProcessingException();
    }
    return baos;
}

Edited:

PDFBox version: 2.0.0 (I tried with the latest version too: 2.0.21)

A link to the PDF file that I'm using to test.
https://drive.google.com/file/d/1vKslaheP7ADlCca75X1jjd2f8Cca7AzU/view?usp=sharing

Conflicting fields:

• When and where -> World region <-> State/area
• Aircraft information ->
  Manufacturer <-> Model
• Flight details -> Last departure point ->
  Country <-> ICAO code
• Flight details -> Planned destination ->
  Country <-> ICAO code

Thanks for the support beforehand.

Thanks to @TilmanHausherr for your support.

Using PDFDebugger you can see that PDF files have an internal combo box for each option of the "parent" combo box where you can take option-value list to load the "nested" combo box.

1. Open the PDF file with PDFDebugger (you need to download the jar of PDFBox app):

   java -jar pdfbox-app-x.x.x.jar PDFDebugger <pdf_file_name>

2. Activate the following option to show PDF content and check them easier: "View -> Show Internal Structure"

3. In the components tree go to "Root -> AcroForm -> Fields" where you can see all the components and their attributes, options, values, etc.

When you know the respective names you can load the "nested" combo box with the following code:

final PDField optionsValuesField = pdComboBox.getAcroForm().getField("optionsValuesFieldName");
final PDComboBox optionsValuesPdComboBox = (PDComboBox) optionsValuesField;

final PDField nestedPdComboBoxField = pdComboBox.getAcroForm().getField("nestedPdComboBoxName");
final PDComboBox nestedPdComboBox = (PDComboBox) nestedPdComboBoxField;

nestedPdComboBox.setOptions(optionsValuesPdComboBox.getOptionsExportValues(), optionsValuesPdComboBox.getOptionsDisplayValues());