title: How to make validation on Put httpmethods?
body: <p>I am getting stuck to make validation on my put/update services</p>
  <pre><code> public Book updateBook (Book book){
          Book existingbook = repository.findById(book.getId()).orElse(null);
          existingbook.setQuantity(book.getQuantity());
          existingbook.setName(book.getName());
          existingbook.setPrice(book.getPrice());
          return repository.save(existingbook);
      }
  </code></pre>
  <p>How to make validation when the user only can set a quantity lower than 100?</p>