code: public Field getKey() {
          String keyName = null;
          for (int i = 0; i < columns.getColumns().size(); i++) {
              if (columns.getColumns().get(i).getKey()) {
                  keyName = columns.getColumns().get(i).getName();
                  break;
              }
          }
          if (keyName != null && !keyName.equals("")) {
              try {
                  Field field = FieldUtil.getField(Class.forName(clazz), keyName);
                  return field;
              } catch (Exception e) {
                  //ignore
                  e.printStackTrace();
              }
          }
          return null;
      }
docs: 获取key值
  
  @return