iText mergeFields in PdfCopy creates invalid pdf

I am working on the task of merging some input PDF documents using iText 5.4.5. The input documents may or may not contain AcroForms and I want to merge the forms as well.

I am using the example pdf files found here and this is the code example:

public class TestForms {

 @Test
 public void testNoForms() throws DocumentException, IOException {
     test("pdf/hello.pdf", "pdf/hello_memory.pdf");
 }

 @Test
 public void testForms() throws DocumentException, IOException {
     test("pdf/subscribe.pdf", "pdf/filled_form_1.pdf");
 }

 private void test(String first, String second) throws DocumentException, IOException {
    OutputStream out = new FileOutputStream("/tmp/out.pdf");
    InputStream stream = getClass().getClassLoader().getResourceAsStream(first);
    PdfReader reader = new PdfReader(new RandomAccessFileOrArray(
            new RandomAccessSourceFactory().createSource(stream)), null);
    InputStream stream2 = getClass().getClassLoader().getResourceAsStream(second);
    PdfReader reader2 = new PdfReader(new RandomAccessFileOrArray(
            new RandomAccessSourceFactory().createSource(stream2)), null);

    Document pdfDocument = new Document(reader.getPageSizeWithRotation(1));
    PdfCopy pdfCopy = new PdfCopy(pdfDocument, out);
    pdfCopy.setFullCompression();
    pdfCopy.setCompressionLevel(PdfStream.BEST_COMPRESSION);
    pdfCopy.setMergeFields();
    pdfDocument.open();
    pdfCopy.addDocument(reader);
    pdfCopy.addDocument(reader2);
    pdfCopy.close();
    reader.close();
    reader2.close();
 }
}

With input files containing forms I get a NullPointerException with or without compression enabled.
With standard input docs, the output file is created but when I open it with Acrobat it says there was a problem (14) and no content is displayed.
With standard input docs AND compression disabled the output is created and Acrobat displays it.

Questions

I previously did this using PdfCopyFields but it's now deprecated in favor of the boolean flag mergeFields in the PdfCopy, is this correct? There's no javadoc on that flag and I couldn't find documentation about it.
Assuming the answer to the previous question is Yes, is there anything wrong with my code? Thanks

Solution

Your usage of PdfCopy.setMergeFields() is correct and your merging code is fine.

The issues you described are because of bugs that have crept into 5.4.5. They should be fixed in rev. 6152 and the fixes will be included in the next release.

Thanks for bringing this to our attention.