Hibernate Criteria 多層次查詢關聯問題 HibernateJava

hibernate存在如下表及關聯:

class House{
  private string houseid;
  private string housename;
}
class Shelf{
  private string shelfid;
  private House house;
}
class Position{
  private string positionid;
  private Shelf shelf;
}
class Warehouse{
  private string warehouseid;
  private Position position;
}

Warehouse外鍵關聯Pisition, Position外鍵關聯Shelf, Shelf外鍵關聯houseid。
現在要對Warehouse使用Criteria查詢, 查詢House的id，可使用如下方法:

Criteria criteria = BaseUtil.getCriteria(Warehouse.class);
criteria.createAlias("position", "position");
criteria.createAlias("position.shelf", "shelf");
criteria.add(Expression.eq("shelf.house.houseid", "111"));

如果要查詢House的name, 必須再關聯House表:

Criteria criteria = BaseUtil.getCriteria(Warehouse.class);
criteria.createAlias("position", "position");
criteria.createAlias("position.shelf", "shelf");
criteria.createAlias("shelf.house", "house");
criteria.add(Expression.eq("house.housename", "name A"));

以上代碼就可以實現了。

可是還會出現一個問題:如果表路徑position已經被關聯過了(比如此criteria是傳入的參數,已經關聯了Alias路徑position, 並查詢過了),則會報錯。解決方法：
檢查criteria裏面關聯的路徑，如果已經關聯，則不再關聯，直接使用就行了。

class CriteriaUtil{
public static Criteria addAlias(CriteriaImpl criteriaImpl, String path, String name){
  if(path == null) return criteriaImpl;
  for(Iterator iter = criteriaImpl.iterateSubcriteria();iter.hasNext();){
    Subcriteria subCriteria = (Subcriteria)iter.next();
    if(path.equals(subCriteria.getPath()))
      return criteriaImpl;
  }
  return criteriaImpl.createAlias(path, name);
}
}

(注：這段代碼有時是存在問題的，不是所有的Criteria 都能轉換爲CriteriaImpl，可能會是Subcriteria。因此，需要確保傳入的參數爲CriteriaImpl)

調用代碼就變成：

Criteria criteria = BaseUtil.getCriteria(Warehouse.class);
CriteriaUtil.addAlias((CriteriaImpl)criteria, "position", "position");
CriteriaUtil.addAlias((CriteriaImpl)criteria, "position.shelf", "shelf");
criteria.add(Expression.eq("shelf.house.houseid", "111"));