I have a very basic query.
If i am using many-to-one relationship, then in mapping file for the class of many-valued end, why do we have <many-to-one> element. cant we use <property> element and in its "type" attirbute mention the class name of single-valued end. besides <property> element could have included optional "cascade" and "outer-join" attribute.
Pls correct me if am wrong. is there any specific reason for having <many-to-one> element.

Thanks in advance.

Property describes a value column, one whose value is wholly dependent on the relevant's entities DB row. many-to-one tells hibernate that it's an entity mapping, where a whole new row in a (usually different) table describes it.

If you used a property element, the field would not be treated as reference to another entity, it would just be an integer or a string or whatever.

In that case in the following link

http://www.hibernate.org/hib_docs/refer ... n-property

There if you see under
5.1.9. property

typename could be:

The class name of a custom type(eg. com.illflow.type.MyCustomType)

What does this mean. i could have hbm.xml file for MyCustomType that could actually have some other table mentioned.

Pls verify my understanding.

Thanks in advance

Think of it this way: custom types must be able to be created only via content of the current table only and of course be saved only in the current table.

An example of custom type would be for instance if you had 3 varchar columns in a table - day, month year - and you'd like to make them available in your entity as a single 'CustomDate' object.

many-to-one is used to map a link to an other entity. That's the way it is.

hi lorban,



That is taken care by the <component> element. i.e a user -defined class that is persisted to the same table as the owning entity. I am still not very clear that then what is the use of having use defined class name in the <property> element

Thanks

to handle custom access to fields...e.g. use field or properties (the defaults provided which you can redefine if you want to - very seldom needed).

Hi max,
i am still not very clear on this. could you pls elaborate on what u mentioned or give some pointer . And my second question still remains unanswered.


"If i am using many-to-one relationship, then in mapping file for the class of many-valued end, why do we have <many-to-one> element. cant we use <property> element and in its "type" attirbute mention the class name of single-valued end. besides <property> element could have included optional "cascade" and "outer-join" attribute.
Pls correct me if am wrong. is there any specific reason for having <many-to-one> element. "

Thanks in advance,

many-to-one has different semantics than a property.

if we merged them you would not have DTD validation.

Thanks for taking out ur valuable time.
So that means it is merely for DTD validations, and not required for anything else. coz as per my understanding, the property that defines it is like any other property, but the type differs. Is this understanding right.

Thanks

yes

Thanks