code: private String buildPosition(String journalName, Long position, Long timestamp) {
          StringBuilder masterBuilder = new StringBuilder();
          if (StringUtils.isNotEmpty(journalName) || position != null || timestamp != null) {
              masterBuilder.append('{');
              if (StringUtils.isNotEmpty(journalName)) {
                  masterBuilder.append("\"journalName\":\"").append(journalName).append("\"");
              }
  
              if (position != null) {
                  if (masterBuilder.length() > 1) {
                      masterBuilder.append(",");
                  }
                  masterBuilder.append("\"position\":").append(position);
              }
  
              if (timestamp != null) {
                  if (masterBuilder.length() > 1) {
                      masterBuilder.append(",");
                  }
                  masterBuilder.append("\"timestamp\":").append(timestamp);
              }
              masterBuilder.append('}');
              return masterBuilder.toString();
          } else {
              return null;
          }
      }
docs: ===========================兼容字段