code: public T one() {
          this.beforeCheck();
  
          String sql = this.buildSelectSQL(true);
  
          T model = this.queryOne(modelClass, sql, paramValues);
  
          ifThen(null != model && null != joinParams,
                  () -> this.setJoin(Collections.singletonList(model)));
  
          return model;
      }
docs: query and find one model
  
  @return one model