code: public DaoInterceptorChain doChain() throws DaoException {
          if (hasNext()) {
              DaoInterceptor interceptor = next();
              current++;
              interceptor.filter(this);
          } else {
              executor.exec(getConnection(), getDaoStatement());
              updateCount += getDaoStatement().getUpdateCount();
          }
          return this;
      }
docs: 继续下一个拦截器,如果已经是最后一个拦截器,那么执行executor.exec
  
  @return 本对象,用于链式操作
  @throws Exception