In the meet-in-the-middle mapping approach, you
control both the relational model and the object model. It is up
to you to define the mappings between these models. Kodo has two
tools to aid meet-in-the-middle mapping. First, the Kodo Workbench
includes a visual interface to wiring your classes and schema together.
Second, the mapping tool's
validate action is useful
to meet-in-the-middle mappers. We examined the mapping tool in
Section 7.1, “Forward Mapping”. The
action verifies that the mapping information for a class
matches the class definition and the existing schema. It throws an
informative exception when your mappings are incorrect.
Example 7.16. Validating Mappings
mappingtool -a validate Magazine.java
mappingtool -a validate package.jdo
buildSchema action we discussed in
Section 7.1, “Forward Mapping” is also somewhat useful
during meet-in-the-middle mapping. Unlike the
validate action, which throws an exception if
your mapping data does not match the existing schema,
buildSchema action assumes your mapping data
is correct, and modifies the schema to match your mappings. This lets
you modify your mapping data manually, but saves you the hassle of
using your database's tools to bring the schema up-to-date.
buildSchema is the default action when you use
JPA mapping defaults (Section 7.4, “Mapping Defaults”).