Hi to all !!
First of all I would like to thank the authors of Hibernate for a great
piece of work.
It really works !!!
I have already successfuly recommended Hibernate to couple of my colleagues.
So the hibernated community is growing ... :)
My question concerns best practices of using composite ID's in collection
elements.
The use case is the following:
Stuff contains a set of StuffUnitFactors. It's a one-to-many relationship:
StuffUnitFactor refers back to Stuff, refers to Unit and contains aditional
property (bidirectional one-to-many)
- property: double factor
- many-to-one Unit
- many-to-one Stuff
I have also overriden the hashCode() and equals() methods on StuffUnitFactor
so that they are equal when stuff && unit are equal
In my code I am using the recommended patern for bi-directional
parent-children relationship:
StuffUnitFactor child= new StuffUnitFactor();
Stuff parent= session.load(parentId);
parent.add(child);
session.save(child);
And then I have found out that it's possible to insert two child elements
into database which are equal !!!
QUESTION:
How can I assure the uniquness of StuffUnitFactor in database ??
Of course the best solution would be if I have a primary key on
StuffUnitFactor like: primary_key(stuff, unit)
I have already tried to use what you recommend:
<composite-element class="warehouse.persistent.StuffUnitFactor">
<property name="factor" type="double" update="true" insert="true"
column="factor" not-null="true" />
<many-to-one name="parent" class="warehouse.persistent.Stuff"
cascade="none" outer-join="auto" update="true" insert="true" column="parent"
not-null="true" />
<many-to-one name="unit" class="warehouse.persistent.Unit"
cascade="none" outer-join="auto" update="true" insert="true" column="unit"
not-null="true" />
</composite-element>
But it explicitly makes primary_key(stuff, unit, factor) which is completly
useless as I want to have unique stuff-unit pair.
Then I tried to make o composite ID on StuffUnitFactor itself - but I could
not get it working as collection element ....
Any ideas, practices ??
My Mapping files are like:
<class
name="warehouse.persistent.Stuff"
table="stuff"
dynamic-update="false"
dynamic-insert="false"
>
<set
name="stuffUnitFactors"
lazy="true"
inverse="true"
cascade="all-delete-orphan"
sort="unsorted"
>
<key
column="parent"
/>
<one-to-many
class="warehouse.persistent.StuffUnitFactor"
/>
</set>
</class>
<class
name="warehouse.persistent.StuffUnitFactor"
table="stuffunitfactor"
dynamic-update="false"
dynamic-insert="false"
>
<id
name="id"
column="id"
type="java.lang.Long"
>
<generator class="sequence">
</generator>
</id>
<property
name="factor"
type="double"
update="true"
insert="true"
column="factor"
not-null="true"
/>
<many-to-one
name="parent"
class="warehouse.persistent.Stuff"
cascade="none"
outer-join="auto"
update="true"
insert="true"
column="parent"
not-null="true"
/>
<many-to-one
name="unit"
class="warehouse.persistent.Unit"
cascade="none"
outer-join="auto"
update="true"
insert="true"
column="unit"
not-null="true"
/>
</class>
thanks for your help
Wojtek Bentkowski
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