Extract comments of specific annotation of a PDF using iText

Question

using iText I am able to get a list of annotations of a PDF. It seems that even replies are annotations themselves.

Extracting them, I look at the contents of the PdfDictionary using this

Set<PdfName> keys = annot.getKeys();
for (PdfName key : keys) {
    System.out.println(key + "," + dictionary.get(key));
}

However, I cannot pinpoint which PdfName I need to use in order to identify replies belong to that certain annotation.

Answer 1

Please take a look at the official documentation, more specifically at the answer to the example How to add an "In Reply To" annotation?

In this answer, I explain how to add an "In reply to" to an existing annotation. Let's open the resulting PDF and let's take a look inside:

As you can see, the annotation with the content "Hello PDF" is stored in an object with number 1. It is an annotation in reply to (IRT) the annotation with object number 2.

In answer to your question: you need to look at the key with value PdfName.IRT and this will give you the object number of the annotation to which the current number is a reply.