Hibernate Criteria 多层次查询关联问题

Java代码


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:

Java代码


Criteria criteria = BaseUtil.getCriteria(Warehouse.
class


);

criteria.createAlias(
"position"

,
"position"

);

criteria.createAlias(
"position.shelf"

,
"shelf"

);

criteria.add(Expression.eq(
"shelf.house.houseid"

,
"111"

));

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:

Java代码


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"

));

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。

Java代码


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()))
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：

Java代码


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"

));