@WebServlet(description = "文件上传",value = {"/file/upload"})
public class FileUpload extends HttpServlet {

 public FileUpload() {
  super();
 }

 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  resp.setHeader("Access-Control-Allow-Origin", "*");
  resp.setHeader("Access-Control-Allow-Methods", "*");
  resp.setHeader("Access-Control-Allow-Headers", "x-requested-with,content-type");
  resp.setContentType("application/json");
  resp.setCharacterEncoding("utf-8");
  //文件上传逻辑


 }

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  doPost(req, resp);
 }

 @Override
 protected void doOptions(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  resp.setHeader("Access-Control-Allow-Credentials", "false");
  resp.setHeader("Access-Control-Allow-Origin", "*");
  resp.setHeader("Access-Control-Allow-Methods", "*");
  resp.setHeader("Access-Control-Allow-Headers", "x-requested-with,content-type");
  resp.setContentType("application/json");
  resp.setCharacterEncoding("utf-8");
  super.doOptions(req, resp);
 }