Hibernate: A Developer's Notebook

6.2. Working with Persistent Enumerations

If you were thinking about it, you may have noticed that we never defined a persistence mapping for the SourceMedia class in the first part of this chapter. That's because our persistent enumerated type is a value that gets persisted as part of one or more entities, rather than being an entity unto itself.

In that light, it's not surprising that we've not yet done any mapping. That happens when it's time to actually use the persistent enumeration.

6.1.1. How do I do that?

Recall that we wanted to keep track of the source media for the music tracks in our jukebox system. That means we want to use the SourceMedia enumeration in our Track mapping. We can simply add a new property tag to the class definition in Track.hbm.xml, as shown in Example 6-3.

Example 6-3. Adding the sourceMedia property to the Track mapping document

... <property name="volume" type="short"> <meta attribute="field-description">How loud to play the track</meta> </property> <property name="sourceMedia" type="com.oreilly.hh.SourceMedia"> <meta attribute="field-description">Media on which track was obtained</meta> <meta attribute="use-in-tostring">true</meta> </property> </class> ...

Because the type of our sourceMedia property names a class that implements the PersistentEnum interface, Hibernate knows to persist it using its built-in enumeration support.

With this addition in place, running ant codegen updates our Track class to include the new property. The signature of the ...