This article demonstrates how to detect the required form fields in an existing PDF document using Spire.PDF for Java.
import com.spire.pdf.fields.PdfField; import com.spire.pdf.widget.PdfFormWidget; public class DetectRequiredFields { public static void main(String[] args) { //load a PDF file PdfDocument doc = new PdfDocument(); doc.loadFromFile("C:\\Users\\Administrator\\Desktop\\Fields.pdf"); //get form widget from the PDF document. PdfFormWidget formWidget = (PdfFormWidget)doc.getForm(); //loop through the fields widget for (int i = 0; i < formWidget.getFieldsWidget().getList().getCapacity(); i++) { //get the specific field PdfField field = (PdfField) formWidget.getFieldsWidget().getList().get_Item(i); //get the field name String fieldName = field.getName(); //determine if the field is required boolean isRequired = field.getRequired(); if (isRequired){ //print the required field System.out.println(fieldName + " is required"); } } } }