Working with Structure Mappings

In an object-relational data-model, structures are user defined data-types or object-types. This is similar to a Java class-it denies attributes or fields in which each attribute is either:

A primitive data type
Another structure
Reference to another structure

TopLink maps each structure to a Java class defined in your object model and defines a descriptor for each class. A StructureMapping class maps nested structures, similar to an AggregateObjectMapping class. However, the structure mapping supports null values and shared aggregates without requiring additional settings (because of the object-relational support of the database).