org.datanucleus.sco.backed
Class PriorityQueue

java.lang.Object
  extended by java.util.AbstractCollection<E>
      extended by java.util.AbstractQueue<E>
          extended by java.util.PriorityQueue
              extended by 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


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