org.datanucleus.store.db4o
Class DB4OStoreManager

java.lang.Object
  org.datanucleus.store.AbstractStoreManager
      org.datanucleus.store.db4o.DB4OStoreManager

All Implemented Interfaces:

org.datanucleus.store.StoreManager

public class DB4OStoreManager
extends org.datanucleus.store.AbstractStoreManager

Store Manager for DB4O (http://www.db4o.com).

DataNucleus will select this StoreManager with URLs of the form "db4o:...". Support for DB4O is for the following URLs

• db4o:{filename} - uses a local DB4O database in the named file (no username/password needed)
• db4o:server:{filename} - embedded DB4O server in the named file (no username/password needed)
• db4o:{hostname}:{port} - uses a remote DB4O database with the specified username/password
These URLs are specific to our support since DB4O doesn't use URLs to define the datastore.

Object Activation and Field Loading

DB4O provides methods to hand out memory versions of the datastore objects. Each object has to be "activated" to have its values accessible. Similarly the object can be "deactivated" when it is no longer needed (freeing up resources, and the link to the disk object). When we retrieve an object from DB4O it activates the object. This makes all fields accessible. If however one of the fields is a PC object (or collection, or map, or array etc) that object itself is not activated. Consequently all fields are accessible from the start (unlike with RDBMS), but the StateManager manages the list of fields that are considered "loaded", and this is initially just those in the DFG (even though others are available). When the user accesses one of these "not-loaded" fields DB4OManager.fetchObject is called and that field is marked as loaded (if it is a SCO mutable it is wrapped, and if it is a PC object it has a StateManager connected and is activated).

Persistence

Each object is persisted on its own, and we dont use DB4O's internal cascade mechanism. Instead the DB4OManager.insertObject, or DB4OManager.updateObject methods are called for each object that is to be persisted/updated. Each call to insertObject/updateObject provides reachability by use of PersistFieldManager.

Deletion

Currently objects are deleted using DB4O's internal cascade mechanism.

Transactions and Connections

Refer to ConnectionFactoryImpl. In simple terms each ObjectManager has a DB4O ObjectContainer associated with it, and this is retained until the end of life of the ObjectManager. With DB4O in server mode this allows use of multiple PMs on the same underlying datastore. With DB4O in file mode you can only have one PM operating on the same underlying datastore at once. This is a DB4O limitation rather than ours.

Field Summary

protected static org.datanucleus.util.Localiser

LOCALISER_DB4O Localiser for messages.

Fields inherited from class org.datanucleus.store.AbstractStoreManager

autoStartMechanism, connectionMgr, fixedDatastore, LOCALISER, nontxConnectionFactoryName, omfContext, persistenceHandler, persistenceHandler2, readOnlyDatastore, schemaHandler, starter, starterInitialised, storeDataMgr, storeManagerKey, storeManagerRuntime, txConnectionFactoryName, valueGenerationMgr

Constructor Summary

DB4OStoreManager(org.datanucleus.ClassLoaderResolver clr, org.datanucleus.OMFContext omfContext)
Constructor for a new DB4O StoreManager.

Method Summary

void	activateObject(com.db4o.ObjectContainer cont, java.lang.Object obj) Convenience method to activate an object, to a depth of 1.
void	activateObject(com.db4o.ObjectContainer cont, java.lang.Object obj, int depth) Convenience method to activate an object, to a depth.
void	close() Release of resources
void	deactivateObject(com.db4o.ObjectContainer cont, java.lang.Object obj) Convenience method to deactivate an object, to a depth of 1.
void	deactivateObject(com.db4o.ObjectContainer cont, java.lang.Object obj, int depth) Convenience method to activate an object, to a depth.
void	deregisterObjectContainer(com.db4o.ObjectContainer cont) Method to deregister an ObjectContainer from this store.
org.datanucleus.store.Extent	getExtent(org.datanucleus.ObjectManager om, java.lang.Class c, boolean subclasses) Accessor for an Extent for a class.
java.lang.Object	getObjectIdForObject(org.datanucleus.ObjectManager om, java.lang.Object pc) Convenience method to get the identity for a Persistable object.
java.util.Collection	getSupportedOptions() Accessor for the supported options in string form
boolean	isStrategyDatastoreAttributed(org.datanucleus.metadata.IdentityStrategy identityStrategy, boolean datastoreIdentityField) Check if the strategy is attributed by the database when the PersistenceCapable object is inserted into the database.
protected void	logConfiguration() Convenience method to log the configuration of this store manager.
void	notifyObjectIsOutdated(org.datanucleus.StateManager sm) Hook for the StateManager to notify us that an object is outdated (no longer valid).
void	registerObjectContainer(com.db4o.ObjectContainer cont) Method to register an ObjectContainer as active on this store.
protected void	registerStoreData(org.datanucleus.store.StoreData data) Method to register some data with the store.

Methods inherited from class org.datanucleus.store.AbstractStoreManager

addClass, addClasses, assertReadOnlyForUpdateOfObject, assertReadOnlyForUpdateOfObject, clearAutoStarter, deregisterAllStoreData, getApiAdapter, getBackingStoreForField, getClassNameForObjectID, getConnection, getConnection, getConnection, getConnection, getConnection, getConnectionDriverName, getConnectionFactory, getConnectionFactory2, getConnectionFactory2Name, getConnectionFactoryName, getConnectionManager, getConnectionPassword, getConnectionURL, getConnectionUserName, getDatastoreDate, getMetaDataManager, getNucleusConnection, getNucleusSequence, getOMFContext, getPersistenceHandler, getPersistenceHandler2, getPropertiesForGenerator, getQueryCacheKey, getRuntimeManager, getSchemaHandler, getStoreManagerKey, getStrategyForNative, getStrategyValue, getStrategyValueForGenerator, getSubClassesForClass, getValueGenerationManager, initialiseAutoStart, manageClassForIdentity, managesClass, newStoreData, performVersionCheck, printInformation, registerConnectionFactory, registerConnectionMgr, removeAllClasses, supportsQueryLanguage, supportsValueStrategy

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOCALISER_DB4O

protected static final org.datanucleus.util.Localiser LOCALISER_DB4O

Localiser for messages.

Constructor Detail

DB4OStoreManager

public DB4OStoreManager(org.datanucleus.ClassLoaderResolver clr,
                        org.datanucleus.OMFContext omfContext)

Constructor for a new DB4O StoreManager. Stores the basic information required for the datastore management.

Parameters:

clr - the ClassLoaderResolver

omfContext - The corresponding ObjectManagerFactory omfContext.

Method Detail

close

public void close()

Release of resources

Specified by:

close in interface org.datanucleus.store.StoreManager

Overrides:

close in class org.datanucleus.store.AbstractStoreManager

logConfiguration

protected void logConfiguration()

Convenience method to log the configuration of this store manager.

Overrides:

logConfiguration in class org.datanucleus.store.AbstractStoreManager

registerStoreData

protected void registerStoreData(org.datanucleus.store.StoreData data)

Method to register some data with the store. This will also register the data with the starter process.

Overrides:

registerStoreData in class org.datanucleus.store.AbstractStoreManager

Parameters:

data - The StoreData to add

registerObjectContainer

public void registerObjectContainer(com.db4o.ObjectContainer cont)

Method to register an ObjectContainer as active on this store. Will load up all known class mapping information into the datastore container.

Parameters:

cont - ObjectContainer

deregisterObjectContainer

public void deregisterObjectContainer(com.db4o.ObjectContainer cont)

Method to deregister an ObjectContainer from this store. ObjectContainers are deregistered when about to be closed and hence not interested in more class mapping information.

Parameters:

cont - ObjectContainer

notifyObjectIsOutdated

public void notifyObjectIsOutdated(org.datanucleus.StateManager sm)

Hook for the StateManager to notify us that an object is outdated (no longer valid). The most common case is that the state of the PC becomes HOLLOW. This is especially important for object databases employing implicit storing from the main memory to the database (like DB4O).

Specified by:

notifyObjectIsOutdated in interface org.datanucleus.store.StoreManager

Overrides:

notifyObjectIsOutdated in class org.datanucleus.store.AbstractStoreManager

Parameters:

sm - StateManager of object

activateObject

public void activateObject(com.db4o.ObjectContainer cont,
                           java.lang.Object obj)

Convenience method to activate an object, to a depth of 1.

Parameters:

cont - ObjectContainer where the object resides

obj - The object

activateObject

public void activateObject(com.db4o.ObjectContainer cont,
                           java.lang.Object obj,
                           int depth)

Convenience method to activate an object, to a depth.

Parameters:

cont - ObjectContainer where the object resides

obj - The object

depth - The depth to activate to

deactivateObject

public void deactivateObject(com.db4o.ObjectContainer cont,
                             java.lang.Object obj)

Convenience method to deactivate an object, to a depth of 1.

Parameters:

cont - ObjectContainer where the object resides

obj - The object

deactivateObject

public void deactivateObject(com.db4o.ObjectContainer cont,
                             java.lang.Object obj,
                             int depth)

Convenience method to activate an object, to a depth.

Parameters:

cont - ObjectContainer where the object resides

obj - The object

depth - The depth to activate to

getObjectIdForObject

public java.lang.Object getObjectIdForObject(org.datanucleus.ObjectManager om,
                                             java.lang.Object pc)

Convenience method to get the identity for a Persistable object.

Parameters:

om - The Object Manager

pc - The object

Returns:

The identity

isStrategyDatastoreAttributed

public boolean isStrategyDatastoreAttributed(org.datanucleus.metadata.IdentityStrategy identityStrategy,
                                             boolean datastoreIdentityField)

Check if the strategy is attributed by the database when the PersistenceCapable object is inserted into the database. "datastore-identity" cases will be datastore attributed (since we cant store the id anywhere). "application-identity" cases will be datastore attributed if using "IDENTITY" strategy.

Specified by:

isStrategyDatastoreAttributed in interface org.datanucleus.store.StoreManager

Overrides:

isStrategyDatastoreAttributed in class org.datanucleus.store.AbstractStoreManager

Parameters:

identityStrategy - the identityStrategy

datastoreIdentityField - Whether this is for the surrogate datastore identity field

Returns:

if the object for the strategy is attributed by the database

getExtent

public org.datanucleus.store.Extent getExtent(org.datanucleus.ObjectManager om,
                                              java.lang.Class c,
                                              boolean subclasses)

Accessor for an Extent for a class.

Specified by:

getExtent in interface org.datanucleus.store.StoreManager

Overrides:

getExtent in class org.datanucleus.store.AbstractStoreManager

Parameters:

om - The Object Manager

c - The class requiring the Extent

subclasses - Whether to include subclasses of 'c'

Returns:

The Extent.

getSupportedOptions

public java.util.Collection getSupportedOptions()

Accessor for the supported options in string form

Specified by:

getSupportedOptions in interface org.datanucleus.store.StoreManager

Overrides:

getSupportedOptions in class org.datanucleus.store.AbstractStoreManager