I need advice on how to map a rather complex field in one of my persistent classes.

I have a java.util.Map that maps from a key to one of several possible objects. It's probably best to use a silly example:

Alice -> PERSON(wife)
Bob -> TEACHER(daughter's teacher)
Duke -> DOG

(a TEACHER extends PERSON, although I'm not always sure this is the case in real life.) In the actual business logic it's a bit more complex since the key also constraints the class of the target - it's more like:

LIGHT_BULBS -> LIGHTBULB_MANUFACTURER(...) or
-> LIGHTBULB_PURCHASER(...)

but never

! LIGHT_BULBS -> TONER_CARTRIDGE_MANUFACTURER

Maybe I'm missing something obvious, but I see this producing three tables:

FIE: the table that contains the bulk of the object, and contains a one-to-many 'map' relationship to FEE.

FEE: the table that contains the map, linking key and a one-to-one relationship to FOE, FUM, FAH

FOE: a table that contains PERSONs
FUM: a table that contains TEACHERs
FAH: a table that contains DOGs

Is this the simplest approach? Is it possible to store all targets in a single column - I want to avoid having one field for each possible type, for both business logic and practical reasons.

Finally, what are the Xdoclet tags for all of this?!

Amazing how asking for help seems to shake something loose so you can find the answer yourself.

This seems to answer my problems, and with a lot less effort than I first feared:



The main downside is that this approach is that a serializable object is opaque - the RHS of the map can't be used in Hibernate queries.[/code]

I spoke too soon - this seems to produce a table that provides a general map, not one keyed to a specific instance....

forget XDoclet for this.


Looks like you need a <many-to-any>