I am generating Java objects from an XML schema using xjc. I would like to reference the same element multiple times within the document using IDREF. I would also like to constrain the objects referenced by IDREF to a specific type. I'd like to do this for the purposes of schema validation, but also so that in the Java code, the referenced object is returned as a specific type instead of type Object. For example, say I want a schema to describe the following:
<teams>
<team id="team1">
<coach>coachz</coach>
<player>homestar</player>
<player>marzipan</player>
<player>strongsad</player>
<player>strongbad</player>
</team>
<team id="team2">
<coach>bubs</coach>
<player>homesar</player>
<player>thecheat</player>
<player>poopsmith</player>
<player>bubs</player>
</team>
<team id="allstars">
<coach>poopsmith</coach>
<player>coachz</player>
<player>bubs</player>
<player>kingoftown</player>
<player>strongbad</player>
</team>
</teams>
<people>
<person id="coachz">Coach Z</person>
<person id="homesar">Homesar</person>
<person id="homestar">Homestar</person>
<person id="strongbad">Strong Bad</person>
<person id="strongsad">Strong Sad</person>
<person id="marzipan">Marzipan</person>
<person id="bubs">Bubs</person>
<person id="kingoftown">King of Town</person>
<person id="poopsmith">The Poopsmith</person>
<person id="thecheat">The Cheat</person>
</people>
I can define player
like this:
<xs:element name="player" type="xs:IDREF" maxOccurs="unbounded"/>
but then in the Java code, when I try to retrieve a player it will come back as type object, and I have to cast it to a person. At that point, if someone has mistakenly referenced a Team object, I have errors to deal with that could have been caught at validation. I want to specify something like this:
<xs:element name="player" type="xs:IDREF"
reftype="person"
maxOccurs="unbounded" />
But as far as I can tell, there is no way to specify a type as I have done here with the contrived attribute 'reftype'. Can this be done, using IDREF? If not, is there another method?