com.db4o.config
Interface Configuration
- public interface Configuration
configuration interface for db4o.
This interface contains methods to configure db4o. All methods
should be called before starting the db4o engine.
Db4o.configure()
returns the single global Configuration object.
activationDepth
public void activationDepth(int depth)
- sets the activation depth to the specified value.
Why activation?
During the instantiation
of stored objects from persistent storage, the instantiation of members
needs to be limited to a certain depth. Otherwise a possible root object
would completely instantiate all stored objects to memory. db4o uses a
preconfigured "activation depth" of 5.
If an object is returned in an
ObjectSet as a result of a
query
object.member1.member2.member3.member4.member5 will be instantiated.
member5 will have all it's members set to null. Primitive
types will have the default values respectively. In db4o terminology, the
state of member5 is called DEACTIVATED. member5 can be
activated by calling
ObjectContainer#activate(member5, depth).
Note that raising the global activation depth will consume more memory and
have negative effects on the performance of first-time retrievals. Lowering
the global activation depth needs more individual activation work but can
increase performance of queries.
- Parameters:
depth - the desired global activation depth.- See Also:
-
configuring classes individually
objectClass
public ObjectClass objectClass(java.lang.String className)
- returns an
ObjectClass object
to configure the specified class.
- Parameters:
className - the fully qualified name of the class to be configured.
- Returns:
- an instance of an
ObjectClass
object for configuration.