Hibernate Criteria 多层次查询关联有关问题(转)

Hibernate Criteria 多层次查询关联问题(转)

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http://terrencemail.javaeye.com/blog/197821

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;??}??

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_r.eq("shelf.house.houseid",?"111"));??

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

Criteria criteria = BaseUtil.getCriteria(Warehouse.class); criteria.createAlias("position", "position"); criteria.createAlias("position.shelf", "shelf"); criteria.createAlias("shelf.house", "house"); criteria.add(expression_r.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);??}??}??

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()))                  

(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_r.eq("shelf.house.houseid",?"111"));?