code: public void invoke(Connection conn) throws Exception {
          for (DaoStatement st : sts) {
              if (st == null) {
                  if (log.isInfoEnabled())
                      log.info("Found a null DaoStatement(SQL), ingore it ~~");
                  continue;
              }
              current = 0;
              daoStatement = st;
              this.connection = conn;
              doChain();
          }
      }
docs: 这是DaoExecutor会执行的方法,拦截器内不要执行这个方法!! 这里也是拦截器开始生效的地方.