JDO - JDO Class Types

JDO Class Types

JDO provides a means of transparent persistence of objects of user defined classes. With JDO there are actually 3 types of classes.

Persistence Capable classes are classes whose instances can be persisted to a datastore. JDO provide the mechanism for persisting these instances, and they are core to JDO. These classes need to be enhanced according to a JDO Meta-Data specification before use within a JDO environment.
Persistence Aware classes are classes that manipulate Persistence Capable instances through direct attribute manipulation. These classes are typically enhanced with very minimal JDO Meta-Data. The enhancement process performs very little changes to these classes.
Normal classes are classes that aren't themselves persistable, and have no knowledge of persistence either. These classes are totally unchanged in JDO, and require no JDO Meta-Data whatsoever.

Classes are defined as PersistenceCapable either by XML MetaData, like this

<class name="MyClass">
    ...
</class>

or, in JDO2.1, using Annotations. Like this

@PersistenceCapable
public class MyClass
{
    ...
}

Classes are defined as PersistenceAware either by XML MetaData, like this

<class name="MyClass" persistence-modifier="persistence-aware"/>

or, in JDO2.1, using Annotations. Like this

@PersistenceAware
public class MyClass
{
    ...
}