org.jpox.sco
Class Queue

java.lang.Object
  java.util.AbstractCollection<E>
      java.util.AbstractQueue
          org.jpox.sco.Queue

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.lang.Iterable, java.util.Collection, java.util.Queue, org.jpox.sco.SCO, org.jpox.sco.SCOCollection, org.jpox.sco.SCOLazyLoading, org.jpox.sco.SCOMtoN, org.jpox.store.query.Queryable

public class Queue
extends java.util.AbstractQueue
implements org.jpox.sco.SCOCollection, org.jpox.sco.SCOMtoN, org.jpox.sco.SCOLazyLoading, java.lang.Cloneable, org.jpox.store.query.Queryable, java.io.Serializable

A mutable second-class Queue object, representing a field in a class, and containing elements of a particular type. Uses a "delegate" as a local store for the Queue. Uses a "backing store" (ListStore) to represent the datastore. The "delegate" is updated with the "backing store" information at necessary intervals.

Modes of Operation

The user can operate the collection 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 collection has been loaded from its backing store and does this as necessary. Some methods (size(), contains()) just check if everything is loaded and use the delegate if possible, otherwise going direct to the datastore.

Version:

$Revision: 1.8 $

See Also:

Serialized Form

Field Summary

protected boolean	allowNulls
protected org.jpox.store.scostore.ListStore	backingStore The "backing store" (for use when not serialised).
protected java.util.Queue	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 org.jpox.StateManager	ownerSM
protected boolean	useCache Whether to use "delegate" caching.

Constructor Summary

Queue(org.jpox.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 c) Method to add a collection of elements.
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.
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.
void	detach(org.jpox.state.FetchPlanState state) Method to detach the PersistenceCapable elements of this container.
java.lang.Object	detachCopy(org.jpox.state.FetchPlanState state) Method to return a detached copy of the container.
boolean	equals(java.lang.Object o) Equality operator.
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.
int	hashCode() Hashcode operator.
protected void	init(org.jpox.StateManager ownerSM, java.lang.String fieldName) Initialisation method.
boolean	isEmpty() Accessor for whether the Collection is empty.
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
void	makeTransient(org.jpox.state.FetchPlanState state) Method to make transient all elements of this container.
org.jpox.store.expression.QueryExpression	newQueryStatement() Method to generate a QueryStatement for the SCO.
org.jpox.store.expression.QueryExpression	newQueryStatement(java.lang.Class candidate_class) Method to return a QueryStatement, using the specified candidate class.
org.jpox.store.query.Query.ResultObjectFactory	newResultObjectFactory(org.jpox.store.expression.QueryExpression stmt, boolean ignoreCache, java.lang.Class resultClass, boolean useFetchPlan) Method to return a ResultObjectFactory for the SCO.
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	removeAll(java.util.Collection c) Method to remove a Collection of elements.
boolean	retainAll(java.util.Collection c) Method to retain a Collection of elements (and remove all others).
void	runReachability(java.util.Set reachables) Method to run reachability on this SCO.
void	setValueFrom(java.lang.Object o, boolean forUpdate) Mutator for setting using an object.
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 org.jpox.StateManager ownerSM

fieldName

protected java.lang.String fieldName

fieldNumber

protected int fieldNumber

elementType

protected java.lang.Class elementType

allowNulls

protected boolean allowNulls

backingStore

protected org.jpox.store.scostore.ListStore backingStore

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

delegate

protected java.util.Queue 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

Queue

public Queue(org.jpox.StateManager ownerSM,
             java.lang.String fieldName)

Constructor.

Parameters:

ownerSM - The State Manager for this set.

fieldName - Name of the field

Method Detail

init

protected void init(org.jpox.StateManager ownerSM,
                    java.lang.String fieldName)

Initialisation method.

Parameters:

ownerSM - The owner StateManager

fieldName - The name of the field of the SCO.

getElementType

public java.lang.Class getElementType()

Accessor for the element type.

Specified by:

getElementType in interface org.jpox.sco.SCOCollection

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 org.jpox.sco.SCOLazyLoading

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 org.jpox.sco.SCOCollection

Parameters:

element - The element

fieldNumber - Number of field in the element

value - New value for this field

setValueFrom

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

Mutator for setting using an object.

Specified by:

setValueFrom in interface org.jpox.sco.SCO

Parameters:

o - The object to set from

forUpdate - Whether to update the datastore with this value

getFieldName

public java.lang.String getFieldName()

Accessor for the field name.

Specified by:

getFieldName in interface org.jpox.sco.SCO

Returns:

The field name

getOwner

public java.lang.Object getOwner()

Accessor for the owner object.

Specified by:

getOwner in interface org.jpox.sco.SCO

Returns:

The owner object

unsetOwner

public void unsetOwner()

Method to unset the owner and field information.

Specified by:

unsetOwner in interface org.jpox.sco.SCO

makeDirty

public void makeDirty()

Utility to mark the object as dirty

runReachability

public void runReachability(java.util.Set reachables)

Method to run reachability on this SCO.

Specified by:

runReachability in interface org.jpox.sco.SCO

Parameters:

reachables - List of StateManagers reachable so far

makeTransient

public void makeTransient(org.jpox.state.FetchPlanState state)

Method to make transient all elements of this container. All elements that are PersistenceCapable will be made transient.

Specified by:

makeTransient in interface org.jpox.sco.SCO

Parameters:

state - State for the fetchplan process

detach

public void detach(org.jpox.state.FetchPlanState state)

Method to detach the PersistenceCapable elements of this container.

Specified by:

detach in interface org.jpox.sco.SCO

Parameters:

state - State for the detachment process

detachCopy

public java.lang.Object detachCopy(org.jpox.state.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 org.jpox.sco.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 org.jpox.sco.SCO

Parameters:

value - The new (collection) value

newQueryStatement

public org.jpox.store.expression.QueryExpression newQueryStatement()

Method to generate a QueryStatement for the SCO.

Specified by:

newQueryStatement in interface org.jpox.store.query.Queryable

Returns:

The QueryStatement

newQueryStatement

public org.jpox.store.expression.QueryExpression newQueryStatement(java.lang.Class candidate_class)

Method to return a QueryStatement, using the specified candidate class.

Specified by:

newQueryStatement in interface org.jpox.store.query.Queryable

Parameters:

candidate_class - the candidate class

Returns:

The QueryStatement

newResultObjectFactory

public org.jpox.store.query.Query.ResultObjectFactory newResultObjectFactory(org.jpox.store.expression.QueryExpression stmt,
                                                                             boolean ignoreCache,
                                                                             java.lang.Class resultClass,
                                                                             boolean useFetchPlan)

Method to return a ResultObjectFactory for the SCO.

Specified by:

newResultObjectFactory in interface org.jpox.store.query.Queryable

Parameters:

stmt - The QueryStatement

ignoreCache - Whether to ignore the cache

resultClass - Whether to create objects of a particular class

useFetchPlan - whether to use the fetch plan to retrieve fields in the same query

Returns:

The ResultObjectFactory

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 org.jpox.sco.SCO

Overrides:

clone in class java.lang.Object

Returns:

A clone of the object

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 org.jpox.sco.SCOMtoN

Overrides:

contains in class java.util.AbstractCollection

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

Specified by:

isEmpty in interface org.jpox.store.query.Queryable

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

Specified by:

iterator in class java.util.AbstractCollection

Returns:

The iterator

size

public int size()

Accessor for the size of the Collection.

Specified by:

size in interface java.util.Collection

Specified by:

size in class java.util.AbstractCollection

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.AbstractCollection

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.AbstractCollection

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

Overrides:

add in class java.util.AbstractQueue

Parameters:

element - The element to add

Returns:

Whether it was added successfully.

addAll

public boolean addAll(java.util.Collection c)

Method to add a collection of elements.

Specified by:

addAll in interface java.util.Collection

Overrides:

addAll in class java.util.AbstractQueue

Parameters:

c - 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.AbstractQueue

offer

public boolean offer(java.lang.Object element)

Method to offer an element to the Queue.

Specified by:

offer in interface java.util.Queue

Parameters:

element - The element to offer

Returns:

Whether it was added successfully.

peek

public java.lang.Object peek()

Method to peek at the next element in the Queue.

Specified by:

peek in interface java.util.Queue

Returns:

The element

poll

public java.lang.Object poll()

Method to poll the next element in the Queue.

Specified by:

poll in interface java.util.Queue

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.AbstractCollection

Parameters:

element - The Element to remove

Returns:

Whether it was removed successfully.

removeAll

public boolean removeAll(java.util.Collection c)

Method to remove a Collection of elements.

Specified by:

removeAll in interface java.util.Collection

Overrides:

removeAll in class java.util.AbstractCollection

Parameters:

c - 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

loadFromStore

protected void loadFromStore()

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