oracle.toplink.indirection
Class IndirectSet

java.lang.Object
oracle.toplink.indirection.IndirectSet

All Implemented Interfaces:

java.lang.Cloneable, java.util.Collection, IndirectContainer, java.io.Serializable, java.util.Set

Direct Known Subclasses:

EJBIndirectSet

public class IndirectSet

extends java.lang.Object

implements java.util.Set, IndirectContainer, java.lang.Cloneable, java.io.Serializable

IndirectSet is an example implementation of the Set protocol that allows a domain class to take advantage of TopLink Indirection without having to declare its instance variable as a ValueHolderInterface.

To use an IndirectSet:

• Declare the appropriate instance variable with type Set (or Collection).
• Send the message #useTransparentCollection() to the appropriate CollectionMapping.
• Send the message #useCollectionClass(IndirectSet.class) to the same CollectionMapping. (The order of these two message sends is significant.)

TopLink will place an IndirectSet in the instance variable when the containing domain object is read from the datatabase. With the first message sent to the IndirectSet, the contents are fetched from the database and normal Set behavior is resumed.

Implementation notes:

• The Set interface is implemented by delegating nearly every message to the Set held on to by the 'delegate' instance variable. (The 'delegate' will be either a HashSet or yet another IndirectSet.)
• The IndirectContainer interface is implemented in a straightforward fashion:
  • #get- and #setValueHolder() are implemented as simple accessors for the 'valueHolder' instance variable. (Note that #setValueHolder() clears out the 'delegate' instance variable, since its contents are invalidated by the arrival of a new value holder.)
  • #isInstantiated() is simply delegated to the value holder.
• TopLink requires that the Cloneable interface be implemented. The #clone() method must clone the 'delegate'. (The implementation here uses reflection to invoke the #clone() method because it is not included in the common interface shared by IndirectSet and its base delegate class, HashSet; namely, Set.)
• TopLink requires that the Serializable interface be implemented.
• The database read is ultimately triggered when one of the "delegated" methods makes the first call to #getDelegate(), which in turn calls #buildDelegate(), which sends the message #getValue() to the value holder. The value holder performs the database read.
• For debugging purposes, #toString() will not trigger a database read. This is not required behavior.

Since:

TOPLink/Java 3.0+

See Also:

CollectionMapping, Serialized Form

Constructor Summary

IndirectSet()
Construct an empty IndirectSet.

IndirectSet(java.util.Collection c)
Construct an IndirectSet containing the elements of the specified collection.

IndirectSet(int initialCapacity)
Construct an empty IndirectSet with the specified initial capacity.

IndirectSet(int initialCapacity, float loadFactor)
Construct an empty IndirectSet with the specified initial capacity and load factor.

Method Summary

boolean	add(java.lang.Object o)
boolean	addAll(java.util.Collection c)
void	clear()
java.lang.Object	clone()
boolean	contains(java.lang.Object o)
boolean	containsAll(java.util.Collection c)
boolean	equals(java.lang.Object o)
ValueHolderInterface	getValueHolder() Return the valueHolder.
int	hashCode()
boolean	isEmpty()
boolean	isInstantiated() Return whether the contents have been read from the database.
java.util.Iterator	iterator()
boolean	remove(java.lang.Object o)
boolean	removeAll(java.util.Collection c)
boolean	retainAll(java.util.Collection c)
void	setValueHolder(ValueHolderInterface valueHolder) Set the value holder.
int	size()
java.lang.Object[]	toArray()
java.lang.Object[]	toArray(java.lang.Object[] a)
java.lang.String	toString() Use the delegate's #toString(); but wrap it with braces to indicate there is a bit of indirection.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

IndirectSet

public IndirectSet()

Construct an empty IndirectSet.

IndirectSet

public IndirectSet(int initialCapacity)

Construct an empty IndirectSet with the specified initial capacity.

Parameters:

initialCapacity - the initial capacity of the set

Throws:

java.lang.IllegalArgumentException - if the specified initial capacity is negative

IndirectSet

public IndirectSet(int initialCapacity,
                   float loadFactor)

Construct an empty IndirectSet with the specified initial capacity and load factor.

Parameters:

initialCapacity - the initial capacity of the set

loadFactor - the load factor of the set

Throws:

java.lang.IllegalArgumentException - if the specified initial capacity is negative

IndirectSet

public IndirectSet(java.util.Collection c)

Construct an IndirectSet containing the elements of the specified collection.

Parameters:

c - the initial elements of the set

Method Detail

add

public boolean add(java.lang.Object o)

Specified by:

add in interface java.util.Set

See Also:

Set.add(java.lang.Object)

addAll

public boolean addAll(java.util.Collection c)

Specified by:

addAll in interface java.util.Set

See Also:

Set.addAll(java.util.Collection)

clear

public void clear()

Specified by:

clear in interface java.util.Set

See Also:

Set.clear()

clone

public java.lang.Object clone()

See Also:

This will result in a database query if necessary.

contains

public boolean contains(java.lang.Object o)

Specified by:

contains in interface java.util.Set

See Also:

Set.contains(java.lang.Object)

containsAll

public boolean containsAll(java.util.Collection c)

Specified by:

containsAll in interface java.util.Set

See Also:

Set.containsAll(java.util.Collection)

equals

public boolean equals(java.lang.Object o)

Specified by:

equals in interface java.util.Set

See Also:

Set.equals(java.lang.Object)

getValueHolder

public ValueHolderInterface getValueHolder()

Return the valueHolder.

Specified by:

getValueHolder in interface IndirectContainer

Returns:

oracle.toplink.indirection.ValueHolderInterface A representation of the valueholder * which this container uses

hashCode

public int hashCode()

Specified by:

hashCode in interface java.util.Set

See Also:

Set.hashCode()

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Set

See Also:

Set.isEmpty()

isInstantiated

public boolean isInstantiated()

Return whether the contents have been read from the database.

Specified by:

isInstantiated in interface IndirectContainer

iterator

public java.util.Iterator iterator()

Specified by:

iterator in interface java.util.Set

See Also:

Set.iterator()

remove

public boolean remove(java.lang.Object o)

Specified by:

remove in interface java.util.Set

See Also:

Set.remove(java.lang.Object)

removeAll

public boolean removeAll(java.util.Collection c)

Specified by:

removeAll in interface java.util.Set

See Also:

Set.removeAll(java.util.Collection)

retainAll

public boolean retainAll(java.util.Collection c)

Specified by:

retainAll in interface java.util.Set

See Also:

Set.retainAll(java.util.Collection)

setValueHolder

public void setValueHolder(ValueHolderInterface valueHolder)

Set the value holder. Note that the delegate must be cleared out.

Specified by:

setValueHolder in interface IndirectContainer

size

public int size()

Specified by:

size in interface java.util.Set

See Also:

Set.size()

toArray

public java.lang.Object[] toArray()

Specified by:

toArray in interface java.util.Set

See Also:

Set.toArray()

toArray

public java.lang.Object[] toArray(java.lang.Object[] a)

Specified by:

toArray in interface java.util.Set

See Also:

Set.toArray(java.lang.Object[])

toString

public java.lang.String toString()

Use the delegate's #toString(); but wrap it with braces to indicate there is a bit of indirection. Don't allow this method to trigger a database read.

See Also:

AbstractCollection.toString()