org.datanucleus.sco.backed
Class PriorityQueue

java.lang.Object
  java.util.AbstractCollection<E>
      java.util.AbstractQueue<E>
          java.util.PriorityQueue
              org.datanucleus.sco.backed.PriorityQueue

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.lang.Iterable, java.util.Collection, java.util.Queue, SCO, SCOCollection, SCOContainer, SCOMtoN

public class PriorityQueue
extends java.util.PriorityQueue
implements SCOCollection, SCOMtoN, java.lang.Cloneable, java.io.Serializable

A mutable second-class PriorityQueue object. This class extends PriorityQueue, using that class to contain the current objects, and the backing ListStore to be the interface to the datastore. A "backing store" is not present for datastores that dont use DatastoreClass, or if the container is serialised or non-persistent.

Modes of Operation

The user can operate the list in 2 modes. The cached mode will use an internal cache of the elements (in the "delegate") reading them at the first opportunity and then using the cache thereafter. The non-cached mode will just go direct to the "backing store" each call.

Mutators

When the "backing store" is present any updates are passed direct to the datastore as well as to the "delegate". If the "backing store" isn't present the changes are made to the "delegate" only.

Accessors

When any accessor method is invoked, it typically checks whether the container has been loaded from its "backing store" (where present) and does this as necessary. Some methods (size()) just check if everything is loaded and use the delegate if possible, otherwise going direct to the datastore.

See Also:

Serialized Form

Field Summary

protected boolean	allowNulls
protected ListStore	backingStore The "backing store" (for use when not serialised).
protected java.util.PriorityQueue	delegate The internal "delegate".
protected java.lang.Class	elementType
protected java.lang.String	fieldName
protected int	fieldNumber
protected boolean	isCacheLoaded Status flag whether the collection is loaded into the cache.
protected java.lang.Object	owner
protected StateManager	ownerSM
protected boolean	useCache Whether to use "delegate" caching.

Constructor Summary

PriorityQueue(StateManager ownerSM, java.lang.String fieldName)
Constructor.

Method Summary

boolean	add(java.lang.Object element) Method to add an element to the Collection.
boolean	addAll(java.util.Collection elements) Method to add a collection of elements.
protected void	addQueuedOperation(QueuedOperation op) Convenience method to add a queued operation to the operations we perform at commit.
void	attachCopy(java.lang.Object value) Method to return an attached copy of the passed (detached) value.
void	clear() Method to clear the Collection.
java.lang.Object	clone() Creates and returns a copy of this object.
java.util.Comparator	comparator() Accessor for the comparator.
boolean	contains(java.lang.Object element) Accessor for whether an element is contained in the Collection.
boolean	containsAll(java.util.Collection c) Accessor for whether a collection of elements are contained here.
java.lang.Object	detachCopy(FetchPlanState state) Method to return a detached copy of the container.
boolean	equals(java.lang.Object o) Equality operator.
void	flush() Method to flush the changes to the datastore when operating in queued mode.
java.lang.Class	getElementType() Accessor for the element type.
java.lang.String	getFieldName() Accessor for the field name.
java.lang.Object	getOwner() Accessor for the owner object.
java.lang.Object	getValue() Accessor for the unwrapped value that we are wrapping.
int	hashCode() Hashcode operator.
void	initialise() Method to initialise the SCO for use.
void	initialise(java.lang.Object o, boolean forInsert, boolean forUpdate) Method to initialise the SCO from an existing value.
boolean	isEmpty() Accessor for whether the Collection is empty.
boolean	isLoaded() Method to return if the SCO has its contents loaded.
java.util.Iterator	iterator() Accessor for an iterator for the Collection.
void	load() Method to effect the load of the data in the SCO.
protected void	loadFromStore() Method to load all elements from the "backing store" where appropriate.
void	makeDirty() Utility to mark the object as dirty
boolean	offer(java.lang.Object element) Method to offer an element to the Queue.
java.lang.Object	peek() Method to peek at the next element in the Queue.
java.lang.Object	poll() Method to poll the next element in the Queue.
boolean	remove(java.lang.Object element) Method to remove an element from the Collection.
boolean	remove(java.lang.Object element, boolean allowCascadeDelete) Method to remove an element from the collection, and observe the flag for whether to allow cascade delete.
boolean	removeAll(java.util.Collection elements) Method to remove a Collection of elements.
boolean	retainAll(java.util.Collection c) Method to retain a Collection of elements (and remove all others).
int	size() Accessor for the size of the Collection.
java.lang.Object[]	toArray() Method to return the Collection as an array.
java.lang.Object[]	toArray(java.lang.Object[] a) Method to return the Collection as an array.
java.lang.String	toString() Method to return the Collection as a String.
void	unsetOwner() Method to unset the owner and field information.
void	updateEmbeddedElement(java.lang.Object element, int fieldNumber, java.lang.Object value) Method to update an embedded element in this collection.
protected java.lang.Object	writeReplace() The writeReplace method is called when ObjectOutputStream is preparing to write the object to the stream.

Methods inherited from class java.util.AbstractQueue

element, remove

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

owner

protected java.lang.Object owner

ownerSM

protected StateManager ownerSM

fieldName

protected java.lang.String fieldName

fieldNumber

protected int fieldNumber

elementType

protected java.lang.Class elementType

allowNulls

protected boolean allowNulls

backingStore

protected ListStore backingStore

The "backing store" (for use when not serialised).

delegate

protected java.util.PriorityQueue delegate

The internal "delegate".

useCache

protected boolean useCache

Whether to use "delegate" caching.

isCacheLoaded

protected boolean isCacheLoaded

Status flag whether the collection is loaded into the cache.

Constructor Detail

PriorityQueue

public PriorityQueue(StateManager ownerSM,
                     java.lang.String fieldName)

Constructor.

Parameters:

ownerSM - The State Manager for this set.

fieldName - Name of the field

Method Detail

initialise

public void initialise(java.lang.Object o,
                       boolean forInsert,
                       boolean forUpdate)

Method to initialise the SCO from an existing value.

Specified by:

initialise in interface SCO

Parameters:

o - The object to set from

forInsert - Whether the object needs inserting in the datastore with this value

forUpdate - Whether to update the datastore with this value

initialise

public void initialise()

Method to initialise the SCO for use.

Specified by:

initialise in interface SCO

getValue

public java.lang.Object getValue()

Accessor for the unwrapped value that we are wrapping.

Specified by:

getValue in interface SCO

Returns:

The unwrapped value

getElementType

public java.lang.Class getElementType()

Accessor for the element type.

Returns:

the element type contained in the collection

load

public void load()

Method to effect the load of the data in the SCO. Used when the SCO supports lazy-loading to tell it to load all now.

Specified by:

load in interface SCOContainer

isLoaded

public boolean isLoaded()

Method to return if the SCO has its contents loaded. If the SCO doesn't support lazy loading will just return true.

Specified by:

isLoaded in interface SCOContainer

Returns:

Whether it is loaded

loadFromStore

protected void loadFromStore()

Method to load all elements from the "backing store" where appropriate.

flush

public void flush()

Method to flush the changes to the datastore when operating in queued mode. Does nothing in "direct" mode.

Specified by:

flush in interface SCOContainer

addQueuedOperation

protected void addQueuedOperation(QueuedOperation op)

Convenience method to add a queued operation to the operations we perform at commit.

Parameters:

op - The operation

updateEmbeddedElement

public void updateEmbeddedElement(java.lang.Object element,
                                  int fieldNumber,
                                  java.lang.Object value)

Method to update an embedded element in this collection.

Specified by:

updateEmbeddedElement in interface SCOCollection

Parameters:

element - The element

fieldNumber - Number of field in the element

value - New value for this field

getFieldName

public java.lang.String getFieldName()

Accessor for the field name.

Specified by:

getFieldName in interface SCO

Returns:

The field name

getOwner

public java.lang.Object getOwner()

Accessor for the owner object.

Specified by:

getOwner in interface SCO

Returns:

The owner object

unsetOwner

public void unsetOwner()

Method to unset the owner and field information.

Specified by:

unsetOwner in interface SCO

makeDirty

public void makeDirty()

Utility to mark the object as dirty

detachCopy

public java.lang.Object detachCopy(FetchPlanState state)

Method to return a detached copy of the container. Recurses through the elements so that they are likewise detached.

Specified by:

detachCopy in interface SCO

Parameters:

state - State for detachment process

Returns:

The detached container

attachCopy

public void attachCopy(java.lang.Object value)

Method to return an attached copy of the passed (detached) value. The returned attached copy is a SCO wrapper. Goes through the existing elements in the store for this owner field and removes ones no longer present, and adds new elements. All elements in the (detached) value are attached.

Specified by:

attachCopy in interface SCO

Parameters:

value - The new (collection) value

clone

public java.lang.Object clone()

Creates and returns a copy of this object.

Mutable second-class Objects are required to provide a public clone method in order to allow for copying PersistenceCapable objects. In contrast to Object.clone(), this method must not throw a CloneNotSupportedException.

Specified by:

clone in interface SCO

Overrides:

clone in class java.lang.Object

Returns:

A clone of the object

comparator

public java.util.Comparator comparator()

Accessor for the comparator.

Overrides:

comparator in class java.util.PriorityQueue

Returns:

The comparator

contains

public boolean contains(java.lang.Object element)

Accessor for whether an element is contained in the Collection.

Specified by:

contains in interface java.util.Collection

Specified by:

contains in interface SCOMtoN

Overrides:

contains in class java.util.PriorityQueue

Parameters:

element - The element

Returns:

Whether the element is contained here

containsAll

public boolean containsAll(java.util.Collection c)

Accessor for whether a collection of elements are contained here.

Specified by:

containsAll in interface java.util.Collection

Overrides:

containsAll in class java.util.AbstractCollection

Parameters:

c - The collection of elements.

Returns:

Whether they are contained.

equals

public boolean equals(java.lang.Object o)

Equality operator.

Specified by:

equals in interface java.util.Collection

Overrides:

equals in class java.lang.Object

Parameters:

o - The object to compare against.

Returns:

Whether this object is the same.

hashCode

public int hashCode()

Hashcode operator.

Specified by:

hashCode in interface java.util.Collection

Overrides:

hashCode in class java.lang.Object

Returns:

The Hash code.

isEmpty

public boolean isEmpty()

Accessor for whether the Collection is empty.

Specified by:

isEmpty in interface java.util.Collection

Overrides:

isEmpty in class java.util.AbstractCollection

Returns:

Whether it is empty.

iterator

public java.util.Iterator iterator()

Accessor for an iterator for the Collection.

Specified by:

iterator in interface java.lang.Iterable

Specified by:

iterator in interface java.util.Collection

Overrides:

iterator in class java.util.PriorityQueue

Returns:

The iterator

peek

public java.lang.Object peek()

Method to peek at the next element in the Queue.

Specified by:

peek in interface java.util.Queue

Overrides:

peek in class java.util.PriorityQueue

Returns:

The element

size

public int size()

Accessor for the size of the Collection.

Specified by:

size in interface java.util.Collection

Overrides:

size in class java.util.PriorityQueue

Returns:

The size

toArray

public java.lang.Object[] toArray()

Method to return the Collection as an array.

Specified by:

toArray in interface java.util.Collection

Overrides:

toArray in class java.util.PriorityQueue

Returns:

The array

toArray

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

Method to return the Collection as an array.

Specified by:

toArray in interface java.util.Collection

Overrides:

toArray in class java.util.PriorityQueue

Parameters:

a - The array to write the results to

Returns:

The array

toString

public java.lang.String toString()

Method to return the Collection as a String.

Overrides:

toString in class java.util.AbstractCollection

Returns:

The string form

add

public boolean add(java.lang.Object element)

Method to add an element to the Collection.

Specified by:

add in interface java.util.Collection

Specified by:

add in interface java.util.Queue

Overrides:

add in class java.util.PriorityQueue

Parameters:

element - The element to add

Returns:

Whether it was added successfully.

addAll

public boolean addAll(java.util.Collection elements)

Method to add a collection of elements.

Specified by:

addAll in interface java.util.Collection

Overrides:

addAll in class java.util.AbstractQueue

Parameters:

elements - The collection of elements to add.

Returns:

Whether they were added successfully.

clear

public void clear()

Method to clear the Collection.

Specified by:

clear in interface java.util.Collection

Overrides:

clear in class java.util.PriorityQueue

offer

public boolean offer(java.lang.Object element)

Method to offer an element to the Queue.

Specified by:

offer in interface java.util.Queue

Overrides:

offer in class java.util.PriorityQueue

Parameters:

element - The element to offer

Returns:

Whether it was added successfully.

poll

public java.lang.Object poll()

Method to poll the next element in the Queue.

Specified by:

poll in interface java.util.Queue

Overrides:

poll in class java.util.PriorityQueue

Returns:

The element (now removed)

remove

public boolean remove(java.lang.Object element)

Method to remove an element from the Collection.

Specified by:

remove in interface java.util.Collection

Overrides:

remove in class java.util.PriorityQueue

Parameters:

element - The Element to remove

Returns:

Whether it was removed successfully.

remove

public boolean remove(java.lang.Object element,
                      boolean allowCascadeDelete)

Method to remove an element from the collection, and observe the flag for whether to allow cascade delete.

Specified by:

remove in interface SCOCollection

Parameters:

element - The element

allowCascadeDelete - Whether to allow cascade delete

Returns:

Whether the element was removed

removeAll

public boolean removeAll(java.util.Collection elements)

Method to remove a Collection of elements.

Specified by:

removeAll in interface java.util.Collection

Overrides:

removeAll in class java.util.AbstractCollection

Parameters:

elements - The collection to remove

Returns:

Whether they were removed successfully.

retainAll

public boolean retainAll(java.util.Collection c)

Method to retain a Collection of elements (and remove all others).

Specified by:

retainAll in interface java.util.Collection

Overrides:

retainAll in class java.util.AbstractCollection

Parameters:

c - The collection to retain

Returns:

Whether they were retained successfully.

writeReplace

protected java.lang.Object writeReplace()
                                 throws java.io.ObjectStreamException

The writeReplace method is called when ObjectOutputStream is preparing to write the object to the stream. The ObjectOutputStream checks whether the class defines the writeReplace method. If the method is defined, the writeReplace method is called to allow the object to designate its replacement in the stream. The object returned should be either of the same type as the object passed in or an object that when read and resolved will result in an object of a type that is compatible with all references to the object.

Returns:

the replaced object

Throws:

java.io.ObjectStreamException