org.datanucleus.store.types.backed

Class Map

java.lang.Object

java.util.AbstractMap

org.datanucleus.store.types.simple.Map

org.datanucleus.store.types.backed.Map

All Implemented Interfaces:

Serializable, Cloneable, Map, BackedSCO, SCO, SCOContainer, SCOMap

public class Map
extends Map
implements BackedSCO

A mutable second-class Map object. Uses a "delegate" as a local store for the Map. Uses a "backing store" (SetStore) to represent the datastore. The "delegate" is updated with the "backing store" information at necessary intervals.

Modes of Operation

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

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	allowNulls
protected MapStore	backingStore
protected boolean	isCacheLoaded
protected boolean	queued
protected boolean	useCache

Fields inherited from class org.datanucleus.store.types.simple.Map

delegate, LOCALISER, ownerMmd, ownerOP

Constructor Summary

Constructors

Constructor and Description
Map(ObjectProvider op, AbstractMemberMetaData mmd) Constructor, using the ObjectProvider of the "owner" and the field name.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Method to clear the Map.
Object	clone() Creates and returns a copy of this object.
boolean	containsKey(Object key) Utility to check if a key is contained in the Map.
boolean	containsValue(Object value) Utility to check if a value is contained in the Map.
Set	entrySet() Accessor for the set of entries in the Map.
boolean	equals(Object o) Method to check the equality of this map, and another.
Object	get(Object key) Accessor for the value stored against a key.
Store	getBackingStore()
Object	getValue() Accessor for the unwrapped value that we are wrapping.
int	hashCode() Method to generate a hashcode for this Map.
void	initialise() Method to initialise the SCO for use.
void	initialise(Object o, boolean forInsert, boolean forUpdate) Method to initialise the SCO from an existing value.
boolean	isEmpty() Method to return if the Map is empty.
boolean	isLoaded() Method to return if the SCO has its contents loaded.
Set	keySet() Accessor for the set of keys in the Map.
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.
Object	put(Object key, Object value) Method to add a value to the Map.
void	putAll(Map m) Method to add a Map of values to this map.
Object	remove(Object key) Method to remove a value from the Map.
int	size() Method to return the size of the Map.
String	toString() Method to return a string form of this Map.
void	unsetOwner() Method to unset the owner and field information.
void	updateEmbeddedKey(Object key, int fieldNumber, Object newValue) Method to update an embedded key in this map.
void	updateEmbeddedValue(Object value, int fieldNumber, Object newValue) Method to update an embedded value in this map.
Collection	values() Accessor for the set of values in the Map.
protected Object	writeReplace() The writeReplace method is called when ObjectOutputStream is preparing to write the object to the stream.

Methods inherited from class org.datanucleus.store.types.simple.Map

attachCopy, detachCopy, getFieldName, getOwner, makeDirty

Methods inherited from class java.lang.Object

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

Field Detail

allowNulls

protected transient boolean allowNulls

backingStore

protected transient MapStore backingStore

useCache

protected transient boolean useCache

isCacheLoaded

protected transient boolean isCacheLoaded

queued

protected transient boolean queued

Constructor Detail

Map

public Map(ObjectProvider op,
   AbstractMemberMetaData mmd)

Constructor, using the ObjectProvider of the "owner" and the field name.

Parameters:

op - The owner ObjectProvider

mmd - Metadata for the member

Method Detail

initialise

public void initialise(Object o,
              boolean forInsert,
              boolean forUpdate)

Method to initialise the SCO from an existing value.

Specified by:

initialise in interface SCO

Overrides:

initialise in class Map

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

Overrides:

initialise in class Map

getValue

public Object getValue()

Accessor for the unwrapped value that we are wrapping.

Specified by:

getValue in interface SCO

Overrides:

getValue in class Map

Returns:

The unwrapped value

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

Overrides:

load in class Map

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

Overrides:

isLoaded in class Map

Returns:

Whether it is loaded

loadFromStore

protected void loadFromStore()

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

getBackingStore

public Store getBackingStore()

Specified by:

getBackingStore in interface BackedSCO

updateEmbeddedKey

public void updateEmbeddedKey(Object key,
                     int fieldNumber,
                     Object newValue)

Method to update an embedded key in this map.

Specified by:

updateEmbeddedKey in interface SCOMap

Overrides:

updateEmbeddedKey in class Map

Parameters:

key - The key

fieldNumber - Number of field in the key

newValue - New value for this field

updateEmbeddedValue

public void updateEmbeddedValue(Object value,
                       int fieldNumber,
                       Object newValue)

Method to update an embedded value in this map.

Specified by:

updateEmbeddedValue in interface SCOMap

Overrides:

updateEmbeddedValue in class Map

Parameters:

value - The value

fieldNumber - Number of field in the value

newValue - New value for this field

unsetOwner

public void unsetOwner()

Method to unset the owner and field information.

Specified by:

unsetOwner in interface SCO

Overrides:

unsetOwner in class Map

clone

public 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 Map

Returns:

Clone of the object

containsKey

public boolean containsKey(Object key)

Utility to check if a key is contained in the Map.

Specified by:

containsKey in interface Map

Overrides:

containsKey in class Map

Parameters:

key - The key to check

Returns:

Whether it is contained

containsValue

public boolean containsValue(Object value)

Utility to check if a value is contained in the Map.

Specified by:

containsValue in interface Map

Overrides:

containsValue in class Map

Parameters:

value - The value to check

Returns:

Whether it is contained

entrySet

public Set entrySet()

Accessor for the set of entries in the Map.

Specified by:

entrySet in interface Map

Overrides:

entrySet in class Map

Returns:

Set of entries

equals

public boolean equals(Object o)

Method to check the equality of this map, and another.

Specified by:

equals in interface Map

Overrides:

equals in class Map

Parameters:

o - The map to compare against.

Returns:

Whether they are equal.

get

public Object get(Object key)

Accessor for the value stored against a key.

Specified by:

get in interface Map

Overrides:

get in class Map

Parameters:

key - The key

Returns:

The value.

hashCode

public int hashCode()

Method to generate a hashcode for this Map.

Specified by:

hashCode in interface Map

Overrides:

hashCode in class Map

Returns:

The hashcode.

isEmpty

public boolean isEmpty()

Method to return if the Map is empty.

Specified by:

isEmpty in interface Map

Overrides:

isEmpty in class Map

Returns:

Whether it is empty.

keySet

public Set keySet()

Accessor for the set of keys in the Map.

Specified by:

keySet in interface Map

Overrides:

keySet in class Map

Returns:

Set of keys.

size

public int size()

Method to return the size of the Map.

Specified by:

size in interface Map

Overrides:

size in class Map

Returns:

The size

values

public Collection values()

Accessor for the set of values in the Map.

Specified by:

values in interface Map

Overrides:

values in class Map

Returns:

Set of values.

toString

public String toString()

Method to return a string form of this Map.

Overrides:

toString in class AbstractMap

Returns:

String form of this Map.

clear

public void clear()

Method to clear the Map.

Specified by:

clear in interface Map

Overrides:

clear in class Map

put

public Object put(Object key,
         Object value)

Method to add a value to the Map.

Specified by:

put in interface Map

Overrides:

put in class Map

Parameters:

key - The key for the value.

value - The value

Returns:

The previous value against this key (if any).

putAll

public void putAll(Map m)

Method to add a Map of values to this map.

Specified by:

putAll in interface Map

Overrides:

putAll in class Map

Parameters:

m - The Map to add

remove

public Object remove(Object key)

Method to remove a value from the Map.

Specified by:

remove in interface Map

Overrides:

remove in class Map

Parameters:

key - The key for the value.

Returns:

The value removed.

writeReplace

protected Object writeReplace()
                       throws 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.

Overrides:

writeReplace in class Map

Returns:

the replaced object

Throws:

ObjectStreamException