Hibernate Criteria 多层次查询关联问题

http://terrencemail.iteye.com/blog/197821
第 16 章  条件查询(Criteria Queries) http://oss.org.cn/ossdocs/framework/hibernate/reference-v3_zh-cn/querycriteria.html
hibernate存在如下表及关联:

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外键关联Pisition, Position外键关联Shelf, Shelf外键关联houseid。
现在要对Warehouse使用Criteria查询, 查询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")); 

如果要查询House的name, 必须再关联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")); 

以上代码就可以实现了。

可是还会出现一个问题:如果表路径position已经被关联过了(比如此criteria是传入的参数,已经关联了Alias路径position, 并查询过了),则会报错。解决方法：
检查criteria里面关联的路径，如果已经关联，则不再关联，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：这段代码有时是存在问题的，不是所有的Criteria 都能转换为CriteriaImpl，可能会是Subcriteria。因此，需要确保传入的参数为CriteriaImpl)

调用代码就变成： 

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"));