Right, but in the following example taken from your blog (here:
http://fabiomaulo.blogspot.com/2009/05/nhibernate-versioning.html) the <id>
tag has no property name, no column attribute and no <column> tag.
<class name="Sample">
<id type="int">
<generator class="hilo"/>
</id>
<version name="Version" access="backfield"/>
<property name="Description"/>
</class>
Is NHibernate ignoring the id or is it inferring a column name or is
something else going on?
On Sun, Aug 2, 2009 at 12:42 AM, Fabio Maulo <[email protected]> wrote:
> by default the column name is the property name.You can specify the column
> name adding 'column' attribute or <column> tag.
>
> 2009/8/1 Everett Muniz <[email protected]>
>
> Thanks for the links Fabio.
>> I've checked the links along with several similar references to the <id>
>> tag on your blog. I also went back and checked the NHibernate docs.
>>
>> If I'm understanding the docs and what you've written correctly, all that
>> I need to exclude the POID property is omit the name attribute from the <id>
>> tag. What I'm still not getting is how the mapping knows the database
>> column to use. I guess the fact that the docs say the column attribute is
>> optional is confusing me.
>>
>> Is there a convention in play here? I mean, is the column name being
>> inferred? This blog entry,
>> http://fabiomaulo.blogspot.com/2009/05/nhibernate-versioning.html, seems
>> to suggest that the column name may be being inferred if I'm reading it
>> right.
>>
>> On Sat, Aug 1, 2009 at 6:10 PM, Fabio Maulo <[email protected]> wrote:
>>
>>> ah... btw the entity UserMitaMita (of the previous mail) is the entity
>>> persisted in the DB and does not have a property ID.
>>> In that post who has the ID is exactly the in memory wellknow instance
>>> (Country).
>>>
>>> 2009/8/1 Fabio Maulo <[email protected]>
>>>
>>> The post is for another stuff.
>>>> What I'm saying you is that you can work without declaring a property to
>>>> represent the POID in your entities.
>>>> In my blog you can find other examples where I'm using an entity without
>>>> the ID.
>>>> This is another old post
>>>> http://fabiomaulo.blogspot.com/2008/11/entities-behavior-injection.html
>>>> There you can see an entity with ID and the Invoice entity without ID
>>>> and with behaviour injected.
>>>>
>>>> 2009/8/1 Mike Nichols <[email protected]>
>>>>
>>>>
>>>>> @Fabio,
>>>>> This would only work if the values are static correct? I looked at
>>>>> your blog post on this (
>>>>> http://fabiomaulo.blogspot.com/2009/08/from-db-
>>>>> to-ram-wellknowinstancetype.html<http://fabiomaulo.blogspot.com/2009/08/from-db-%0Ato-ram-wellknowinstancetype.html>for
>>>>> those listening)
>>>>> and while this is useful for those unchanging values like countries
>>>>> and so on I am not sure how this could be applied here.
>>>>>
>>>>>
>>>>>
>>>>> On Jul 31, 9:03 pm, Fabio Maulo <[email protected]> wrote:
>>>>> > In NH you can have an entity without the ID and the ID only for
>>>>> persistence
>>>>> > (without a private filed).In uNhAddIns or in my blog you can find
>>>>> > various examples the last is:
>>>>> > Entity:
>>>>> > public class UserMitaMita
>>>>> > {
>>>>> > public virtual string Name { get; set; }
>>>>> > public virtual Country Country { get; set; }}
>>>>> >
>>>>> > Mapping
>>>>> > <class name="UserMitaMita">
>>>>> > <id type="int">
>>>>> > <generator class="hilo"/>
>>>>> > </id>
>>>>> > <property name="Name"/>
>>>>> > <property name="Country" type="Country"/>
>>>>> > </class>
>>>>> >
>>>>> > 2009/7/31 Everett Muniz <[email protected]>
>>>>> >
>>>>> >
>>>>> >
>>>>> > > For those of you doing DDD with NHibernate...
>>>>> >
>>>>> > > Is it pretty typical to run into scenarios where the way your value
>>>>> objects
>>>>> > > are used with the domain requires a class mapping with its
>>>>> attendant <id>
>>>>> > > requirement? I guess what I'm asking is whether having to support
>>>>> an ID
>>>>> > > within my value object for the sake of persistence is just a fact
>>>>> of life
>>>>> > > related to the oft-lamented impedance mismatch between objects and
>>>>> > > relational databases? I know I can map the ID to a private field
>>>>> so that
>>>>> > > from the domain point-of-view it doesn't exist but it feels like
>>>>> cruft in my
>>>>> > > value object. Before I just accept the compromise I wanted to see
>>>>> if I'm
>>>>> > > overlooking something.
>>>>> >
>>>>> > > If you care about the specific scenario that prompted the question
>>>>> read on,
>>>>> > > otherwise ignore the rest...
>>>>> >
>>>>> > > The system we're developing has all sorts of objects related to
>>>>> drawing and
>>>>> > > many have a color associated with them. Sounds simple I know. The
>>>>> catch is
>>>>> > > that the color actually used to draw an object in a given context
>>>>> is
>>>>> > > determined by applying a strategy that often depends on the data
>>>>> associated
>>>>> > > with that drawing context.
>>>>> >
>>>>> > > So, any object that requires a color (some entities some value
>>>>> objects) has
>>>>> > > a Color property of type ColorSource. ColorSource is an abstract
>>>>> class with
>>>>> > > several specializations such as ConstantColorSource and
>>>>> > > SubstringColorSource. These specializations are value objects.
>>>>> > > Any ConstantColorSource/SubstringColorSource instances with the
>>>>> same
>>>>> > > attributes are completely interchangable.
>>>>> >
>>>>> > > However, when it comes to the persistence mapping in NHibernate the
>>>>> most
>>>>> > > natural way to map the relationship of the various objects that
>>>>> refer to a
>>>>> > > ColorSource seems to be creating an independent class mapping for
>>>>> > > ColorSource that employs the inheritance mapping features of
>>>>> NHibernate.
>>>>> > > However, the class mapping approach seems to really depend on ID.
>>>>> As far
>>>>> > > as I can tell NHibernate's answer to value objects is components
>>>>> but I just
>>>>> > > can't figure out how to accomplish the required mapping using
>>>>> components w/o
>>>>> > > a whole lot of duplication.
>>>>> >
>>>>> > --
>>>>> > Fabio Maulo
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Fabio Maulo
>>>>
>>>
>>>
>>>
>>> --
>>> Fabio Maulo
>>>
>>>
>>>
>>
>>
>>
>
>
> --
> Fabio Maulo
>
> >
>
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