com.db4o.config

Interface ObjectClass

All Known Implementing Classes:

Config4Class

public interface ObjectClass

configuration interface for classes.

Use the global CommonConfiguration.objectClass(Object) to configure object class settings.

Method Summary

Methods

Modifier and Type	Method and Description
void	callConstructor(boolean flag) advises db4o to try instantiating objects of this class with/without calling constructors.
void	cascadeOnActivate(boolean flag) sets cascaded activation behaviour.
void	cascadeOnDelete(boolean flag) sets cascaded delete behaviour.
void	cascadeOnUpdate(boolean flag) sets cascaded update behaviour.
void	compare(ObjectAttribute attributeProvider) Deprecated. since version 7.0
void	enableReplication(boolean setting) Deprecated. As of version 8.0 please use generateUUIDs(boolean) and FileConfiguration.generateCommitTimestamps(boolean) instead
void	generateUUIDs(boolean setting) generate UUIDs for stored objects of this class.
void	generateVersionNumbers(boolean setting) Deprecated. As of version 8.0 please use FileConfiguration.generateCommitTimestamps(boolean) instead
void	indexed(boolean flag) turns the class index on or off.
void	maximumActivationDepth(int depth) sets the maximum activation depth to the desired value.
int	minimumActivationDepth() gets the configured minimum activation depth.
void	minimumActivationDepth(int depth) sets the minimum activation depth to the desired value.
ObjectField	objectField(java.lang.String fieldName) returns an ObjectField object to configure the specified field.
void	persistStaticFieldValues() turns on storing static field values for this class.
void	rename(java.lang.String newName) renames a stored class.
void	storeTransientFields(boolean flag) allows to specify if transient fields are to be stored.
void	translate(ObjectTranslator translator) registers a translator for this class.
void	updateDepth(int depth) specifies the updateDepth for this class.

Method Detail

callConstructor

void callConstructor(boolean flag)

advises db4o to try instantiating objects of this class with/without calling constructors.

Not all JDKs / .NET-environments support this feature. db4o will attempt, to follow the setting as good as the environment supports. In doing so, it may call implementation-specific features like sun.reflect.ReflectionFactory#newConstructorForSerialization on the Sun Java 1.4.x/5 VM (not available on other VMs) and FormatterServices.GetUninitializedObject() on the .NET framework (not available on CompactFramework).

This setting may also be set globally for all classes in Configuration.callConstructors(boolean).

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

Parameters:

flag - - specify true, to request calling constructors, specify false to request not calling constructors.

See Also:

Configuration.callConstructors(boolean)

cascadeOnActivate

void cascadeOnActivate(boolean flag)

sets cascaded activation behaviour.

Setting cascadeOnActivate to true will result in the activation of all member objects if an instance of this class is activated.

The default setting is false.

In client-server environment this setting should be used on both client and server.

Can be applied to an open ObjectContainer.

Parameters:

flag - whether activation is to be cascaded to member objects.

See Also:

ObjectField.cascadeOnActivate(boolean), ObjectContainer.activate(java.lang.Object, int), Using callbacks, Why activation?

cascadeOnDelete

void cascadeOnDelete(boolean flag)

sets cascaded delete behaviour.

Setting cascadeOnDelete to true will result in the deletion of all member objects of instances of this class, if they are passed to ObjectContainer.delete(Object).

Caution !
This setting will also trigger deletion of old member objects, on calls to ObjectContainer.store(Object).

An example of the behaviour:
ObjectContainer con;
Bar bar1 = new Bar();
Bar bar2 = new Bar();
foo.bar = bar1;
con.store(foo); // bar1 is stored as a member of foo
foo.bar = bar2;
con.store(foo); // bar2 is stored as a member of foo
The last statement will also delete bar1 from the ObjectContainer, no matter how many other stored objects hold references to bar1.

The default setting is false.

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

Parameters:

flag - whether deletes are to be cascaded to member objects.

See Also:

ObjectField.cascadeOnDelete(boolean), ObjectContainer.delete(Object), Using callbacks

cascadeOnUpdate

void cascadeOnUpdate(boolean flag)

sets cascaded update behaviour.

Setting cascadeOnUpdate to true will result in the update of all member objects if a stored instance of this class is passed to ObjectContainer.store(Object).

The default setting is false. Setting it to true may result in serious performance degradation.

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

Parameters:

flag - whether updates are to be cascaded to member objects.

See Also:

ObjectField.cascadeOnUpdate(boolean), com.db4o.ObjectContainer#set, Using callbacks

compare

void compare(ObjectAttribute attributeProvider)

Deprecated. since version 7.0

registers an attribute provider for special query behavior.

The query processor will compare the object returned by the attribute provider instead of the actual object, both for the constraint and the candidate persistent object.

In client-server environment this setting should be used on both client and server.

Parameters:

attributeProvider - the attribute provider to be used

enableReplication

void enableReplication(boolean setting)

Deprecated. As of version 8.0 please use generateUUIDs(boolean) and FileConfiguration.generateCommitTimestamps(boolean) instead

Must be called before databases are created or opened so that db4o will control versions and generate UUIDs for objects of this class, which is required for using replication.

Parameters:

setting -

generateUUIDs

void generateUUIDs(boolean setting)

generate UUIDs for stored objects of this class. This setting should be used before the database is first created.

Parameters:

setting -

generateVersionNumbers

void generateVersionNumbers(boolean setting)

Deprecated. As of version 8.0 please use FileConfiguration.generateCommitTimestamps(boolean) instead

generate version numbers for stored objects of this class. This setting should be used before the database is first created.

Parameters:

setting -

indexed

void indexed(boolean flag)

turns the class index on or off.

db4o maintains an index for each class to be able to deliver all instances of a class in a query. If the class index is never needed, it can be turned off with this method to improve the performance to create and delete objects of a class.

Common cases where a class index is not needed:
- The application always works with sub classes or super classes.
- There are convenient field indexes that will always find instances of a class.
- The application always works with IDs.

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

maximumActivationDepth

void maximumActivationDepth(int depth)

sets the maximum activation depth to the desired value.

A class specific setting overrides the global setting

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

Parameters:

depth - the desired maximum activation depth

See Also:

Why activation?, cascadeOnActivate(boolean)

minimumActivationDepth

void minimumActivationDepth(int depth)

sets the minimum activation depth to the desired value.

A class specific setting overrides the global setting

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

Parameters:

depth - the desired minimum activation depth

See Also:

Why activation?, cascadeOnActivate(boolean)

minimumActivationDepth

int minimumActivationDepth()

gets the configured minimum activation depth. In client-server environment this setting should be used on both client and server.

Returns:

the configured minimum activation depth.

objectField

ObjectField objectField(java.lang.String fieldName)

returns an ObjectField object to configure the specified field.

Parameters:

fieldName - the name of the field to be configured.

Returns:

an instance of an ObjectField object for configuration.

persistStaticFieldValues

void persistStaticFieldValues()

turns on storing static field values for this class.

By default, static field values of classes are not stored to the database file. By turning the setting on for a specific class with this switch, all non-simple-typed static field values of this class are stored the first time an object of the class is stored, and restored, every time a database file is opened afterwards, after class meta information is loaded for this class (which can happen by querying for a class or by loading an instance of a class).

To update a static field value, once it is stored, you have to the following in this order:
(1) open the database file you are working against
(2) make sure the class metadata is loaded
objectContainer.query().constrain(Foo.class); // Java
objectContainer.Query().Constrain(typeof(Foo)); // C#
(3) change the static member
(4) store the static member explicitly
objectContainer.store(Foo.staticMember); // Java

The setting will be ignored for simple types.

Use this setting for constant static object members.

This option will slow down the process of opening database files and the stored objects will occupy space in the database file.

In client-server environment this setting should be used on both client and server.

This setting can NOT be applied to an open object container.

rename

void rename(java.lang.String newName)

renames a stored class.

Use this method to refactor classes.

In client-server environment this setting should be used on both client and server.

This setting can NOT be applied to an open object container.

Parameters:

newName - the new fully qualified class name.

storeTransientFields

void storeTransientFields(boolean flag)

allows to specify if transient fields are to be stored.
The default for every class is false.

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

Parameters:

flag - whether or not transient fields are to be stored.

translate

void translate(ObjectTranslator translator)

registers a translator for this class.



The use of an ObjectTranslator is not compatible with the use of an internal class ObjectMarshaller.

In client-server environment this setting should be used on both client and server.

This setting can be applied to an open object container.

Parameters:

translator - this may be an ObjectTranslator or an ObjectConstructor

See Also:

ObjectTranslator, ObjectConstructor

updateDepth

void updateDepth(int depth)

specifies the updateDepth for this class.

see the documentation of ObjectContainer.store(Object) for further details.

The default setting is 0: Only the object passed to ObjectContainer.store(Object) will be updated.

In client-server environment this setting should be used on both client and server.

Parameters:

depth - the depth of the desired update for this class.

See Also:

Configuration.updateDepth(int), cascadeOnUpdate(boolean), ObjectField.cascadeOnUpdate(boolean), Using callbacks