Procedure: extracorporeal shock wave lithotripsy and endoscopic drainage of the main pancreatic duct;Drug: pancreatic enzyme(Pancreatin Enteric-coated Capsules or Oryz-Aspergillus Enzyme and Pancreatin Table), antidiabetic medicine(Acarbose Tablets, Glucophage, Glimepirde Tablets) Procedure: extracorporeal shock wave lithotripsy and endoscopic drainage of the main pancreatic duct ...