How to get cascade updates to work w/ composite ids.

arfff · **Posted:** Sat Feb 21, 2004 5:40 pm

I'm putting together an application that uses composite keys for each of the objects. The objects are versioned so basically all the keys look like:

( long seq, int version )

To do this I followed the steps recommended elsewhere and use an id declaration of:

Code:

  <composite-id name="primaryKey" unsaved-value="any">
     <key-property name="id" column="id"/>
     <key-property name="version" column="version"/>
  </composite-id>

and am setting using a SequenceGenerator to generate my key prior to calling session.save ().

The problem, of course, is that Hibernate has no clue when an object is saved or needs saving/updating.

How can I get it to behave properly in sess.save of a linked object?

I've come up with the following solution that seems to work but it seems quite inelegant. Is this the right or only way?

1) I created an implementation of Interceptor and add it to each session that i use

2) I updated the primary key object that I'm using in my classes to include a 'saved' bit that I can tweak:

Code:

    public class FooKVO { 
      public long id; // persisted
      public int version; // persisted
      public boolean saved; // transient
    }

3) in Interceptor.onLoad and Interceptor.onSave i set that bit for applicable objects using:

Code:

     if (o intsanceof Foo) { 
       final Foo foo = (Foo) o; 
       foo.getPrimaryKey ().setSaved (true); 
    }
    return; 

4) I implemented Interceptor.isUnsaved as:

Code:

     if (o intsanceof Foo) { 
       final Foo foo = (Foo) o; 
       if (foo.getPrimaryKey ().getSaved ()) { 
         return Boolean.FALSE;
      }
    }
    return; 

Any thoughts or guidance on this?

TealWren · **Posted:** Sat Feb 21, 2004 9:00 pm

I don't understand your purpose in making the version stamp part of your key.

Hibernate supports a version tag, which will check versions each time you update (by doing an update where version=loaded version and throw a StaleObjectException when the version has changed since you loaded the object).

This wouldn't be part of the key though.

There are two ways (that I know of!) to make an object with a composite key cascade appropriately - first, write an interceptor and use the isUnsaved function to tell Hibernate which objects are new and which aren't. The other (and easier in my opinion) way is to use the version tag, which will cause hibernate to know the object is unsaved when the version has not yet been assigned.

Good luck,
Jenica