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composite-id with autogenerated field

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greg_barton

Post subject: composite-id with autogenerated field

Posted: Wed Aug 27, 2003 6:09 pm

Pro

Joined: Tue Aug 26, 2003 1:24 pm
Posts: 213
Location: Richardson, TX

M'kay, here's the deal...

I'd like to create a data object that has a composite id based off a many to one relationship and a generated id.

I'm generating both the java and ddl from the mapping file. Here's a mapping I've tried, but it isn't generating the code or database structure I'd like. (Well, this one won't even autogenerate code that compiles. :P )

Code:

<class name="DataObject" table="base_data_objects" mutable="true">
    
        <id name="id" type="long">
            <generator class="native"/>
        </id>
        
        <joined-subclass name="SiteDataObject" table="base_site_data_objects">
            
            <composite-id
                name="site_composite"
                unsaved-value="any">

                <key-property name="id" type="long"/>
                <key-many-to-one name="site" class="Site"/>
        
            </composite-id>
            
            <key column="site_composite"/>

        </joined-subclass>

</class>

The SiteDataObject at the moment is a subclass of DataObject, but I can change this if necessary. My main goal is to have a composite key which contains an autogenerated id and many-to-one fields. However, the generated class will have several subclasses that need to share the composite key...

Thanks!

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gavin

Post subject:

Posted: Wed Aug 27, 2003 6:11 pm

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

subclasses do not have ids. the <id> is inherited. I don't understand what you are trying to do.

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greg_barton

Post subject:

Posted: Wed Aug 27, 2003 6:25 pm

Pro

Joined: Tue Aug 26, 2003 1:24 pm
Posts: 213
Location: Richardson, TX

subclasses do not have ids. the <id> is inherited.

Dur...Should have realized that. :)

What I want to do, though, is have a subclass that modifies the id behavior of the superclass. That's not necessary, though. I can get by if a SiteDataObject is at the base of the object heirarchy.

I don't understand what you are trying to do.

Why ask why? :P

At my business we have several locations that generate data, then we aggregate it to a central location. The "Site" object stores site specific info, and each site database has only one site object. The central database will have a table with all Sites. When a SiteDataObject is created at a site, I want it identifiable by it's autogenerated id and site identifier.

So, is this possible?

Thanks!

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gavin

Post subject:

Posted: Wed Aug 27, 2003 6:51 pm

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

You should remodel this as delegation.

What you really have here is a many-to-one association between the SiteData and the Data; ie. the *same* Data row is shared b/w multiple instances of SiteDate. Hibernate does not (and probably should not) let you represent the same row in multiple instances.

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greg_barton

Post subject:

Posted: Wed Aug 27, 2003 7:12 pm

Pro

Joined: Tue Aug 26, 2003 1:24 pm
Posts: 213
Location: Richardson, TX

the *same* Data row is shared b/w multiple instances of SiteDate

No, not really. Maybe a concrete example will help.

Each site generates events. These events are stored on the site database, then periodically copied to the central DB, where they all reside in one table. That's why I need a composite id. The autogenerated id works fine when the data is at the site, but may not be unique when copied to the central database.

Now my mapping file looks like this:

Code:

<class name="SiteDataObject" table="base_site_data_objects">
        <composite-id name="id" unsaved-value="any" class="CompositeSiteID">
            <key-property name="generated_id" type="long"/>
            <key-many-to-one name="site" class="Site"/>
        </composite-id>

        <joined-subclass name="Event" table="events">
            <key ...>
        </joined-subclass>

</class>

My question now is, what should I put in the <key> tag in the joined-subclass?

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greg_barton

Post subject:

Posted: Wed Aug 27, 2003 8:29 pm

Pro

Joined: Tue Aug 26, 2003 1:24 pm
Posts: 213
Location: Richardson, TX

Hmmm... I just tried to post, but it was eaten. Here we go again...

I wrote some <key> XML that fits with the DTD, but when I run SchemaExport I get an exception.

Here's the mapping:

Code:

<class name="SiteDataObject" table="base_site_data_objects">
        <composite-id name="id" unsaved-value="any" class="CompositeSiteID">
            <key-property name="generated_id" type="long"/>
            <key-many-to-one name="site" class="Site"/>
        </composite-id>

        <joined-subclass name="Event" table="events">
            <key><key column="generated_id"/><key column="site"/></key>
        </joined-subclass>

</class>

When I run SchemaExport I get this exception:

Code:

 Error creating schema Foreign key must have same number of columns as referenced primary key
net.sf.hibernate.MappingException: Foreign key must have same number of columns as referenced primary key
    at net.sf.hibernate.mapping.ForeignKey.setReferencedTable(ForeignKey.java:33)
    at net.sf.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:523)
    at net.sf.hibernate.cfg.Configuration.generateDropSchemaScript(Configuration.java:352)
    at net.sf.hibernate.tool.hbm2ddl.SchemaExport.<init>(SchemaExport.java:51)
    at net.sf.hibernate.tool.hbm2ddl.SchemaExport.main(SchemaExport.java:293)

Any ideas? Is my <key> XML right? Since the exception is spawned from mapping.ForeignKey I tend to think not, but the DTD allows that XML...

Thanks!

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greg_barton

Post subject:

Posted: Wed Aug 27, 2003 8:44 pm

Pro

Joined: Tue Aug 26, 2003 1:24 pm
Posts: 213
Location: Richardson, TX

OK, I know I'm replying to myself a lot, but I keep pounding at it. :)

I replaced the <key> mapping with one that still fits with the DTD but makes more sense. Same exception, though. :(

Mapping:

Code:

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gavin

Post subject:

Posted: Thu Aug 28, 2003 12:23 am

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

This last one should work (the previous does NOT, actually, fit the DTD!). You should have the same number of <column>s in the <key> as are in the <id> of the superclass.

What is the mapping for Site?

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greg_barton

Post subject:

Posted: Thu Aug 28, 2003 1:07 pm

Pro

Joined: Tue Aug 26, 2003 1:24 pm
Posts: 213
Location: Richardson, TX

This last one should work (the previous does NOT, actually, fit the DTD!)

Well, it gets past the XML parser without throwing an exception. Really. Try for yourself. hibernate 2.0.3...

Anyway, I've fixed my mapping problem. I had some <many-to-one> and <set> tags in subclasses that I hadn't changed the <key> tags on. Silly me. :)

One last question remains: How do I create <generator> like functionality for my <composite-id>? Can I do that in the mapping, or do I have to create a custom type for the composite-id?

I know this isn't there now, but it would be nice if you could have a <generator> embedded in a <key-property> tag.

Anyway, here's my mapping, with some classes with the sets and many-to-one tags I was talking about above: (properties edited out for brevity...)

Code:

<class name="SiteDataObject" table="base_site_data_objects">
    <composite-id name="id" unsaved-value="any" class="CompositeSiteID">
        <key-property name="generated_id" type="long"/>
        <key-many-to-one name="site" class="Site"/>
    </composite-id>
    <joined-subclass name="Event" table="events">
        <key><key column="generated_id"/><key column="site"/></key>
    </joined-subclass> <!-- Event -->
    <joined-subclass name="Listing" table="listings">
            <key><column name="generated_id"/><column name="site"/></key>
    </joined-subclass> <!-- Listing -->
    <joined-subclass name="MenuItem" table="menu_items">
        <key><column name="generated_id"/><column name="site"/></key>
        <many-to-one name="parent" class="MenuHeirarchyItem">
            <column name="parent_id" unique-key="label-parent"/>
            <column name="parent_site" unique-key="label-parent"/>
        </many-to-one>
        <joined-subclass name="MenuActionItem" table="menu_actions">
            <key><column name="generated_id"/><column name="site"/></key>
            <many-to-one name="listing" outer-join="false" class="Listing">
                <column name="listing_id"/>
                <column name="listing_site"/>
            </many-to-one>
        </joined-subclass> <!-- MenuActionItem -->
        <joined-subclass name="MenuHeirarchyItem" table="menu_heirarchy">
            <key><column name="generated_id"/><column name="site"/></key>
            <set name="children" lazy="true" inverse="true">
                <key><column name="parent_id"/><column name="parent_site"/></key>
                <one-to-many class="MenuItem"/>
            </set>
        </joined-subclass> <!-- MenuHeirarchyItem -->  
    </joined-subclass> <!-- MenuItem -->  
</class> <!-- SiteDataObject -->
<class name="Site" mutable="true" table="sites_sites">
    <id name="id" type="long">
        <generator class="native"/>
    </id>
</class><!-- Site -->

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gavin

Post subject:

Posted: Thu Aug 28, 2003 4:24 pm

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

Quote:

Well, it gets past the XML parser without throwing an exception. Really. Try for yourself. hibernate 2.0.3...

No it doesn't. It prints a WARN (ERROR?) to your console.

Quote:

do I have to create a custom type for the composite-id?

Yes. There is a page on the wiki about this.

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smlghst

Post subject: I have the same problem !!

Posted: Wed Mar 07, 2007 5:09 am

Newbie

Joined: Sat Mar 03, 2007 3:14 am
Posts: 16

I need a UserType composite-id .. that generate one of the ids ..
Where can i find info about that .. i search in the wiki but i m not find nothing !!

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