Hi,

I have three tables:
ship (columns: id, name, ..)
container (columns: id, name, ship..)
box (columns: id, name, container ..)
and corresponding java classes.

A ship contains containers and a container contains boxes.
…
<class name="Container" table="container" dynamic-update="true">
<id name="id" column="id">
<generator class="assigned"/>
</id>
<property name="name" column="name" not-null="true"/>
<many-to-one name="ship" column="ship"/>
<bag name="boxes" inverse="true" lazy="true" cascade="all">
<key column="box"/>
<one-to-many class="Box"/>
</bag>
</class>
<class name="Box" table="box" dynamic-update="true">
<id name="id" column="id">
<generator class="assigned"/>
</id>
<property name="name" column="name" not-null="true"/>
<many-to-one name="container" column="container"/>
</class>

So far so good. Now I want a query like this (search all boxes of a given ship):
Ship myShip = ..;
List boxes = session.createCriteria(Box.class).add(Restrictions.eq("ship", myShip)).list();

That’s why I have add a method getShip() to the class box (for container such a method already exists).
public Project getShip()
{
return getContainer().getShip();
}

But this doesn’t work. Have I to edit the mapping files and if so how? Can I set a relation in the mapping file between box and ship?

Every hint is very appreciated!

Regards, Detlev







Hibernate version: 3
Debug level Hibernate log excerpt:
org.hibernate.QueryException: could not resolve property

Look for examples using createAlias()...

You don't need the getShip() method... I think you're query would be something like this:

List boxes = session.createCriteria(Box.class).createAlias("container","cntr").add(Restrictions.eq("cntr.ship",myShip)).list();

Note: This might not be 100% correct but should get you started in the right direction.

Thank you very much, that works fine.

But what is if I have a fourth table books (ship ==> container ==> box ==> books). Is this also so possible (get all books in a ship)?

Regards, Detlev

It should work indefinitely, but I would be concerned with the efficiency of the query past a certain point.

I think it might be something like this, but I'm not testing any of this code...

List books = session.createCriteria(Book.class).createAlias("box","bx").createAlias("bx.container","cntr").add(Restrictions.eq("cntr.ship",myShip)).list();

Section 15.4 gives several examples.

I am assuming that you're actually going to add some additional Restrictions to this Criteria, otherwise you don't need to do any of this.



Although I guess this method performs a lot more SQL depending on how many containers and boxes you have on a ship.

Thanks a lot four your very good help!

Detlev