Hi, how best should i do that?

I have 3 Tables.

Item, CompItem and Price. One Item can have many Prices, One Item can have many CompItems and one CompItem can have many Prices.

so, i want to have a method with the parameter ItemId. And i want to get back all Prices of that Item and also all Prices of the corresponding CompItems.

So, how best should i do that? I mean, i can do it with a join and several loops. but is this the best approach?

best regards, Philipp

Hi,
I'm new to hibernate but it seems the best approach is to create your mappings as below and a hierarchy of loops like you said . Looping item.compitem.price inside each item.compitem inside each item in the outerloop . In the outer loop you get item.price for the non compitems.

In Item.hbm.xml

map a one to many relationship to Prices
map a second 1 to many relationship to comp items

Item class has a price property
and a compitems property

In CompItem.hbm.xml map a 1 to many relationship to prices

hope this helps.

Hibernate seems to run a separate query for each child object on an obect that you map . I understand the solution to this is including a series of left joins in your hibernate query but I get the following exception when i do this.

org.hibernate.QueryException: illegal attempt to dereference collection

So ,if anybody has a solution to this, that would be great.

Well, i just post my mapping files!

For Item=Artikel it is like that:



and for the Price=Preis it is like that:


Where should i use a collection?

the problem must bei with the set:



when i add this part of code, i get a parse error of the mapping file!

what is wrong with it?

Instead of using joined subclass you might try using "bag" in the item.hbm file for price this maps to a List property in the parent class

So you have an item that has a bag of comp items
and a compitem has a bag of prices
and for items without comp items but a number of prices
you have an item that has a bag of prices

Don't worry about mapping the other direction until you have the direction of parent to children working .

in item.hbm.xml :

<bag name="compcode" table="compcode_table" inverse="true"
cascade="all-delete-orphan">
<key column="Item_ID" />
<one-to-many class="compcode" />
</bag>

<bag name="price" table="Price" inverse="true"
cascade= "all-delete-orphan">
<key column="Item_ID" />
<one-to-many class="Price />
</bag>

in compcode.hbm.xml :

<bag name="price" table="price" inverse="true"
cascade="all-delete-orphan">
<key column="compcode_ID" />
<one-to-many class="Price" />
</bag>

in Compcode database table -create an Item_id field - this matches the id in Item


in Price database table - create a compcode_id field - this matches the id in Compcode

in Price database table - create an item_id fleld - this matches the id in Item

in Item class create a List property for compcodes

in Item class create a List property for prices

in item class create List property for price