The attribute requirements vary, depending on your Java version. When employing Java 2, you can use direct access on private or protected attributes. Refer to Chapter 4, "About TopLink Descriptors" for more information on direct and method access.
When using non-transparent indirection, the attributes must be of the type ValueHolderInterface rather than the original attribute type. The value holder does not instantiate a referenced object until it is needed.
In Java 2, TopLink provides transparent indirection for Collection and List attribute types for any collection mappings. Using transparent indirection does not require the usage of ValueHolderInterface or any other object model requirements.
Refer to "Working with Relationship Mappings" for more information on indirection and transparent indirection.
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