protected void buildPdfDocument(Map model, Document document, PdfWriter writer, HttpServletRequest request, HttpServletResponse response) throws Exception {
Product product = (Product) model.get("product");
if (product == null) throw new NullPointerException("Product not present in the model");
Paragraph header = new Paragraph("Product details");
header.font().setSize(20);
document.add(header);
Paragraph content = new Paragraph(product.getName());
document.add(content);