Using Queries on Variable One-to-One Mappings

TopLink does not provide a method to directly query against variable one-to-one mappings. To query against this type of mapping, combine TopLink DirectQueryKeys and TopLink ReportQueries to create query selection criteria for classes that implement the interface, as follows:

1. Create two DirectQueryKeys to query for the possible implementors of the interface:

   • The first DirectQueryKey is for the class indicator field for the variable one-to-one mapping.

   • The second DirectQueryKey is for the foreign key to the class or table that implements the interface.

2. Create a subSelect statement for each concrete class that implements the interface included in the query selection criteria.

3. Implement a ReportQuery.

Example 99-7 Creating DirectQueryKeys

/* The DirectQueryKeys as generated in the TopLink project Java source code from TopLink Workbench */
…
descriptor.addDirectQueryKey("locationTypeCode","DEALLOCATION.DEALLOCATIONOBJECTTYPE");
descriptor.addDirectQueryKey("locationTypeId","DEALLOCATION.DEALLOCATIONOBJECTID");