com.persistit.ref

Class AbstractReference

java.lang.Object

com.persistit.ref.AbstractReference

All Implemented Interfaces:

PersistitReference, Serializable

public abstract class AbstractReference
extends Object
implements PersistitReference

An abstract superclass for implementations of PersistitReference. A concrete subclass implements the method:

      public Object lookup(Object id)
 

which should return the Object associated with the supplied id, or null if there is none. The meaning of the identifier, and the mechanism used to look up and deserialize the associated object (the referent), are implementation-specific.

Version:

1.0

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected Object	_id
protected boolean	_knownNull
protected Object	_referent

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractReference() No-arg constructor supplied for object serialization/deserialization.
protected	AbstractReference(Object id) Construct a reference using the persistent identity of an object.
protected	AbstractReference(Object id, Object referent) Construct a reference to the referent Object with the supplied persistent identifier.

Method Summary

Modifier and Type	Method and Description
Object	get() Gets the referent object.
protected abstract Object	lookup(Object id) Look up and instantiate an object using its persistent identifier.

Methods inherited from class java.lang.Object

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

Field Detail

_id

protected Object _id

_knownNull

protected boolean _knownNull

_referent

protected transient Object _referent

Constructor Detail

AbstractReference

protected AbstractReference()

No-arg constructor supplied for object serialization/deserialization.

AbstractReference

protected AbstractReference(Object id,
                            Object referent)

Construct a reference to the referent Object with the supplied persistent identifier. For correct operation, the referent Object must be equivalent to the object that would result from invoking lookup on the persistent identifier. the object that would be returned by the lookup

Parameters:

id - The persistent identifier. The value of the id must be associated with a unique referent object, and must be stable over time.

referent - The object identified by the id

AbstractReference

protected AbstractReference(Object id)

Construct a reference using the persistent identity of an object. A subsequent invocation of the get method will cause the object to be looked up and instantiated.

Parameters:

id -

Method Detail

get

public Object get()

Gets the referent object. If the object has already been looked up, or if this reference was created using the two-argument constructor, then this merely returns the object. Otherwise this method attempts to look up and instantiate the object using its persistent identifier.

Specified by:

get in interface PersistitReference

Returns:

The referent object.

lookup

protected abstract Object lookup(Object id)

Look up and instantiate an object using its persistent identifier. Typically this will be done by setting up a Exchange and fetching its value.

Parameters:

id - The identifier

Returns:

The referent object.