code: public Single<String> execute() {
          try {
              ByteArrayOutputStream bos = new ByteArrayOutputStream();
              ObjectOutputStream oos = new ObjectOutputStream(bos);
              oos.writeObject(this);
              oos.flush();
  
              String reqBase64 = new String(Base64.getEncoder().encode(bos.toByteArray()));
              Map<String, Object> map = new HashMap<>();
              map.put("req", reqBase64);
              return SingleRxXian.call("httpClient", "http", map)
                      .flatMap(response -> Single.just(response.dataToStr()));
          } catch (IOException ioe) {
              throw new RuntimeException(ioe);
          }
      }
docs: 异步调用unit执行