Xiamen Transit Visa 144h

Dear Sir or Madame,I have flight from Poland to Maledives Island and I have a holidays there, than I want to go to xiamen via Hong Kong (only transit), and stay in Xiamen for 4 days, and than go to Amsterdam and back to Poland. Is it possible for me to gain a transit visa in Xiamen for 144h hours?I've heard about online application before arrival to Xiamen Airport but I can't find it.Do You know where online I can fill it in? Thank You in advance.