Mapping Question

ignu · **Joined:** Mon Nov 19, 2007 11:10 am **Posts:** 3

I have the following tables:

Customer

StupidTableIDontCareAbout

StupidTableIDontCareAbout has columns:

- CustomerID int IDENTITY(1,1)
- CustomerPropertyICareAbout varchar(32)

Now, I want my Customer Business Object to have a CustomerPropertyICareAbout, without needing a Business Object modeling the StupidTableIDontCareAbout.

Is there a way to map this?

Thanks!

ponetny_swintuch · **Posted:** Mon Nov 19, 2007 1:41 pm

I am not sure if I understood you well, but maybe <join> could help.

Look at the documentation:

Quote:

5.1.18: Using the <join> element, it is possible to map properties of one class to several tables

is this what you want to do?

VampBoy · **Posted:** Mon Nov 19, 2007 1:44 pm

Use a join table.

An example from our code using annotations is that at the class level we declare:

Code:

@SecondaryTables({@SecondaryTable(name = "WE_PROPERTY_PERIOD", pkJoinColumns = {@PrimaryKeyJoinColumn(name = "WE_PROPERTY_PERIOD_ID", referencedColumnName = "WORKFLOW_EVENT_ID")})})

which sets up the table and tells hibernate what column you're joining on.

And then for the property in question:

Code:

    @ManyToOne(fetch = FetchType.EAGER, optional = false)
    @JoinColumn(name = "LOCATION_PROPERTY_ID", unique = false, nullable = false, insertable = true, updatable = false, table = "WE_PROPERTY_PERIOD")

which denotes the table and column that the property maps to.

ignu · **Joined:** Mon Nov 19, 2007 11:10 am **Posts:** 3

Okay, I think join is what I want, but I can't find many examples of <join table=""> usage that don't assume that both tables have the same primary key.

Code:

<class name="Shipment" table="shipment" >
    <id name="ID" column="ship_num">
      <generator class="native" />
    </id>

<!--...-->
    <join table="customer" >
      <key>
        <column name="customer_id" >
      </key>
      <property name='CustomerNotes' column='notes'/>
    </join>

This fails because it tries to join customer.customer_id to shipment.ship_num. How can I specify, in a mapping file, the foreign key?[/code]

ponetny_swintuch · **Posted:** Mon Nov 19, 2007 5:02 pm

Use property-ref attribute of key.

Code:

Quote:

5.1.19. key property-ref (optional): Specifies that the foreign key refers to columns that are not the primary key of the orginal table.

ignu · **Joined:** Mon Nov 19, 2007 11:10 am **Posts:** 3

This mapping (with property-ref)

Code:

<join table="customer" >
      <key property-ref="customer_id" column="customer_id" />
      <property name="CustomerNotes" column="notes"/>
</join>  

Doesn't work (at least not with NHibernate)

SQL Join this generates:

Code:

 inner join customer shipment0_1_ on shipment0_.ship_num=shipment0_1_.customer_id