Working with Array Mappings

In an object-relational data-model, structures can contain arrays (collections of other data types). These arrays can contain primitive data types or collections of other structures. TopLink stores the arrays with their parent structure in the same table.

All elements in the array must be the same data type. The number of elements in an array controls the size of the array. An Oracle database allows arrays of variable sizes (called Varrays).

Oracle8i offers two collection types:

Varray - Used to represent a collection of primitive data or aggregate structures.
Nested table - Similar to varrays except they store information in a separate table from the parent structure's table

TopLink supports arrays of primitive data through the ArrayMapping class. This is similar to DirectCollectionMapping - it represents a collection of primitives in Java. However, the ArrayMapping class does not require an additional table to store the values in the collection.

TopLink supports arrays of aggregate structures through the ObjectArrayMaping class.

TopLink supports nested tables through the NestedTableMapping class.