code: @SuppressWarnings("unchecked")
      private static String converter(String fieldName, Object object) {
          StringBuilder builder = new StringBuilder();
          if (Checker.isNotEmpty(fieldName)) {
              builder.append("\"").append(fieldName).append("\":");
          }
          if (object instanceof Collection) {
              List list = (List) object;
              builder.append("[");
              list.forEach(obj -> builder.append(converter(ValueConsts.EMPTY_STRING, obj)));
              return builder.substring(0, builder.length() - 1) + "],";
          } else if (object instanceof Map) {
              Map map = (Map) object;
              builder.append("{");
              map.forEach((k, v) -> builder.append(converter(k.toString(), v)));
              return builder.substring(0, builder.length() - 1) + "},";
          } else if (Checker.isEmpty(fieldName)) {
              builder.append("\"").append(object).append("\",");
          } else {
              builder.append("\"").append(object).append("\",");
          }
          return builder.toString();
      }
docs: 手动转换 {@link List} 和 {@link Map}
  
  @param fieldName 字段名
  @param object 对象
  
  @return json对象