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Oracle® Coherence Java API Reference
Release 3.6.1.0

E18814-01


com.tangosol.net.cache
Class SimpleOverflowMap

java.lang.Object
  extended by com.tangosol.util.Base
      extended by com.tangosol.util.AbstractKeyBasedMap
          extended by com.tangosol.net.cache.SimpleOverflowMap

All Implemented Interfaces:
java.util.Map

public class SimpleOverflowMap
extends AbstractKeyBasedMap

A non-observable Map implementation that wraps two maps - a front map (assumed to be fast but limited in its maximum size) and a back map (assumed to be slower but much less limited in its maximum size).

The SimpleOverflowMap is not observable, and as such it is assumed to be a passive data structure. In other words, it does not support item expiration or other types of "self-generating" events. As such, it may be more efficient for many common use cases that would benefit from the complete avoidance of event handling. As a second effect of being a passive data structure, the implementation is able to avoid tracking all of its entries; instead it tracks only entries that are in the front map and those that currently have a pending event or an in-flight operation occurring. This means that huge key sets are possible, since only keys in the front map will be managed in memory by the overflow map, but it means that some operations that would benefit from knowing the entire set of keys will be more expensive. Examples of operations that would be less efficient as a result include containsKey(), size(), keySet().iterator(), etc.

Since:
Coherence 3.1
Author:
cp 2005.07.11

Nested Class Summary
protected static class SimpleOverflowMap.FrontFilterConverter
          A combination Filter and Converter used to iterate through the status map in order to iterate through the front keys.
protected  class SimpleOverflowMap.FrontMapListener
          A listener for the front map that moves evictions to the back map.
protected static class SimpleOverflowMap.HashcodeComparator
          A stateless Comparator that compares Object.hashCode() values.
protected  class SimpleOverflowMap.KeyIterator
          An Iterator implementation that attempts to provide the most resilient and most up-to-date view of the keys in the OverflowMap.
protected static class SimpleOverflowMap.Status
          The Status object is used to manage concurrency at the key level for the key-level operations against the Map, to track all the items in the front Map, to manage the state transition for operations occurring against the Map, and to coordinate events across multiple threads.

 

Nested classes/interfaces inherited from class com.tangosol.util.AbstractKeyBasedMap
AbstractKeyBasedMap.EntrySet, AbstractKeyBasedMap.KeySet, AbstractKeyBasedMap.ValuesCollection

 

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

 

Field Summary
static int ENTRY_DELETED
          This event indicates that an entry has been removed from the map.
static int ENTRY_INSERTED
          This event indicates that an entry has been added to the map.
static int ENTRY_UPDATED
          This event indicates that an entry has been updated in the map.
protected  java.util.Map m_mapBack
          The "back" map, which the front overflows to.
protected  ObservableMap m_mapFront
          The "front" map, which is size-limited.
protected  java.util.Map m_mapMiss
          The miss cache; may be null.
protected  SimpleCacheStatistics m_stats
          The CacheStatistics object maintained by this cache.

 

Constructor Summary
SimpleOverflowMap(ObservableMap mapFront, java.util.Map mapBack)
          Construct a SimpleOverflowMap using two specified maps: FrontMap (aka "cache" or "shallow") and BackMap (aka "file" or "deep")
SimpleOverflowMap(ObservableMap mapFront, java.util.Map mapBack, java.util.Map mapMiss)
          Construct a SimpleOverflowMap using three specified maps: Front Map (aka "cache" or "shallow") and Back Map (aka "file" or "deep") Miss Cache

 

Method Summary
protected  SimpleOverflowMap.Status[] beginBulkKeyProcess(java.lang.Object[] aoKey)
          Begin key-level procecessing for any number of keys.
protected  SimpleOverflowMap.Status beginKeyProcess(java.lang.Object oKey)
          Block until a key is available for processing, and return the Status object for that key.
protected  void beginMapProcess()
          Block until this thread has exclusive access to perform operations against the OverflowMap.
 void clear()
          Clear all key/value mappings.
 boolean containsKey(java.lang.Object oKey)
          Returns true if this map contains a mapping for the specified key.
protected  void endBulkKeyProcess(java.lang.Object[] aoKey, SimpleOverflowMap.Status[] aStatus)
          Finish the processing of any number of keys.
protected  void endKeyProcess(java.lang.Object oKey, SimpleOverflowMap.Status status)
          Finish the processing of a single key.
protected  void endMapProcess()
          Release exclusive access for the OverflowMap.
 java.lang.Object get(java.lang.Object oKey)
          Returns the value to which this map maps the specified key.
 java.util.Map getBackMap()
          Returns the back Map.
 CacheStatistics getCacheStatistics()
          Returns the CacheStatistics for this cache.
protected  java.util.List getDeferredList()
          Obtain the List of keys that may have deferred events.
 ObservableMap getFrontMap()
          Returns the front Map.
protected  MapListener getFrontMapListener()
          Get the MapListener for the front map.
 java.util.Map getMissCache()
          Returns the optional miss cache.
protected  java.util.Map getStatusMap()
          Obtain the Map of Status objects for entries managed by this Overflow Map.
protected  ThreadGate getThreadGate()
          Obtain the ThreadGate for managing key-level and Collection-level operations against the Map, versus Map-level operations themselves.
protected  MapListener instantiateFrontMapListener()
          Factory pattern: Front Map Listener.
protected  SimpleOverflowMap.Status instantiateStatus()
          Factory method: Instantiate a Status object.
 boolean isEmpty()
          Returns true if this map contains no key-value mappings.
 boolean isFrontPutBlind()
          Determine if the front Map is more efficiently updated using putAll.
 boolean isNullValuesAllowed()
          Determine if null values are permitted.
protected  java.util.Iterator iterateKeys()
          Create an iterator over the keys in this Map.
protected  void onFrontEvent(MapEvent evt)
          Either handle an event by turning it over to another thread that is processing the key specified by the event, or take responsibility on this thread for deferring the event and registering its immediate side-effects.
protected  void processDeferredEvents()
          Process deferred events, if there are any.
protected  void processFrontEvent(SimpleOverflowMap.Status status, MapEvent evt)
          Process an event.
 java.lang.Object put(java.lang.Object oKey, java.lang.Object oValue)
          Associates the specified value with the specified key in this map.
 void putAll(java.util.Map map)
          Copies all of the mappings from the specified map to this map.
protected static void putOne(java.util.Map map, java.lang.Object oKey, java.lang.Object oValue, boolean fPutBlind)
          Helper to put a value into a map using either the put or putAll method.
 java.lang.Object remove(java.lang.Object oKey)
          Removes the mapping for this key from this map if present.
protected  boolean removeBlind(java.lang.Object oKey)
          Removes the mapping for this key from this map if present.
protected  void setFrontMapListener(MapListener listener)
          Specify the MapListener for the front map.
 void setFrontPutBlind(boolean fUseFrontPutAll)
          Specify whether the front Map is more efficiently updated using putAll.
 void setNullValuesAllowed(boolean fAllowNulls)
          Specify whether null values are permitted.
 int size()
          Returns the number of key-value mappings in this map.
protected static void verifyNoNulls(java.util.Collection collection, java.lang.String sAssert)
          Check the passed collection for nulls, and fail if it contains any.
protected static void warnEventSequence(MapEvent evtOld, MapEvent evtNew)
          Issue a one-time warning that events are being received in an order than cannot be explained by normal operation according to the contracts expected by this OverflowMap.

 

Methods inherited from class com.tangosol.util.AbstractKeyBasedMap
clone, containsValue, entrySet, equals, getAll, hashCode, instantiateEntrySet, instantiateKeySet, instantiateValues, keySet, toString, values

 

Field Detail

ENTRY_INSERTED

public static final int ENTRY_INSERTED
This event indicates that an entry has been added to the map.
See Also:
Constant Field Values

ENTRY_UPDATED

public static final int ENTRY_UPDATED
This event indicates that an entry has been updated in the map.
See Also:
Constant Field Values

ENTRY_DELETED

public static final int ENTRY_DELETED
This event indicates that an entry has been removed from the map.
See Also:
Constant Field Values

m_mapFront

protected ObservableMap m_mapFront
The "front" map, which is size-limited.

m_mapBack

protected java.util.Map m_mapBack
The "back" map, which the front overflows to.

m_mapMiss

protected java.util.Map m_mapMiss
The miss cache; may be null.

m_stats

protected SimpleCacheStatistics m_stats
The CacheStatistics object maintained by this cache.

Constructor Detail

SimpleOverflowMap

public SimpleOverflowMap(ObservableMap mapFront,
                         java.util.Map mapBack)
Construct a SimpleOverflowMap using two specified maps:
Parameters:
mapBack - back map
mapFront - front map

SimpleOverflowMap

public SimpleOverflowMap(ObservableMap mapFront,
                         java.util.Map mapBack,
                         java.util.Map mapMiss)
Construct a SimpleOverflowMap using three specified maps:
Parameters:
mapFront - front map
mapBack - back map
mapMiss - an optional miss cache

Method Detail

clear

public void clear()
Clear all key/value mappings.
Specified by:
clear in interface java.util.Map
Overrides:
clear in class AbstractKeyBasedMap

containsKey

public boolean containsKey(java.lang.Object oKey)
Returns true if this map contains a mapping for the specified key.
Specified by:
containsKey in interface java.util.Map
Overrides:
containsKey in class AbstractKeyBasedMap
Parameters:
oKey - key whose presence in this map is to be tested.
Returns:
true if this map contains a mapping for the specified key, false otherwise.

get

public java.lang.Object get(java.lang.Object oKey)
Returns the value to which this map maps the specified key.
Specified by:
get in interface java.util.Map
Specified by:
get in class AbstractKeyBasedMap
Parameters:
oKey - the key object
Returns:
the value to which this map maps the specified key, or null if the map contains no mapping for this key
See Also:
Map.containsKey(Object)

isEmpty

public boolean isEmpty()
Returns true if this map contains no key-value mappings.
Specified by:
isEmpty in interface java.util.Map
Overrides:
isEmpty in class AbstractKeyBasedMap
Returns:
true if this map contains no key-value mappings

put

public java.lang.Object put(java.lang.Object oKey,
                            java.lang.Object oValue)
Associates the specified value with the specified key in this map.
Specified by:
put in interface java.util.Map
Overrides:
put in class AbstractKeyBasedMap
Parameters:
oKey - key with which the specified value is to be associated
oValue - value to be associated with the specified key
Returns:
previous value associated with specified key, or null if there was no mapping for key

putAll

public void putAll(java.util.Map map)
Copies all of the mappings from the specified map to this map. The effect of this call is equivalent to that of calling put(java.lang.Object, java.lang.Object) on this map once for each mapping in the passed map. The behavior of this operation is unspecified if the passed map is modified while the operation is in progress.
Specified by:
putAll in interface java.util.Map
Overrides:
putAll in class AbstractKeyBasedMap
Parameters:
map - the Map containing the key/value pairings to put into this Map

remove

public java.lang.Object remove(java.lang.Object oKey)
Removes the mapping for this key from this map if present. Expensive: updates both the underlying cache and the local cache.
Specified by:
remove in interface java.util.Map
Overrides:
remove in class AbstractKeyBasedMap
Parameters:
oKey - key whose mapping is to be removed from the map
Returns:
previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values.

size

public int size()
Returns the number of key-value mappings in this map.
Specified by:
size in interface java.util.Map
Overrides:
size in class AbstractKeyBasedMap
Returns:
the number of key-value mappings in this map

iterateKeys

protected java.util.Iterator iterateKeys()
Create an iterator over the keys in this Map.
Specified by:
iterateKeys in class AbstractKeyBasedMap
Returns:
a new instance of an Iterator over the keys in this Map

removeBlind

protected boolean removeBlind(java.lang.Object oKey)
Removes the mapping for this key from this map if present. This method exists to allow sub-classes to optmiize remove functionalitly for situations in which the original value is not required.
Overrides:
removeBlind in class AbstractKeyBasedMap
Parameters:
oKey - key whose mapping is to be removed from the map
Returns:
true iff the Map changed as the result of this operation

getFrontMap

public ObservableMap getFrontMap()
Returns the front Map.

Warning: Direct modifications of the returned map may cause unpredictable behavior of the Overflow Map.

Returns:
the front Map

getBackMap

public java.util.Map getBackMap()
Returns the back Map.

Warning: Direct modifications of the returned map may cause unpredictable behavior of the Overflow Map.

Returns:
the back Map

getMissCache

public java.util.Map getMissCache()
Returns the optional miss cache.

Warning: Direct modifications of the returned map may cause unpredictable behavior of the Overflow Map.

Returns:
the miss cache, or null if there is no miss cache

getCacheStatistics

public CacheStatistics getCacheStatistics()
Returns the CacheStatistics for this cache.
Returns:
a CacheStatistics object

getThreadGate

protected ThreadGate getThreadGate()
Obtain the ThreadGate for managing key-level and Collection-level operations against the Map, versus Map-level operations themselves.
Returns:
the ThreadGate for the OverflowMap

getStatusMap

protected java.util.Map getStatusMap()
Obtain the Map of Status objects for entries managed by this Overflow Map. There will be a Status object for each entry in the front map, and a Status object for each key that has a current operation underway.
Returns:
the Map of Status objects

getDeferredList

protected java.util.List getDeferredList()
Obtain the List of keys that may have deferred events.
Returns:
the List of keys of deferred-event Status objects

isNullValuesAllowed

public boolean isNullValuesAllowed()
Determine if null values are permitted. By default, they are not.
Returns:
true iff null values are permitted

setNullValuesAllowed

public void setNullValuesAllowed(boolean fAllowNulls)
Specify whether null values are permitted.
Parameters:
fAllowNulls - pass true to allow null values; false to disallow

isFrontPutBlind

public boolean isFrontPutBlind()
Determine if the front Map is more efficiently updated using putAll. (The use of putAll instead of put is called put-blind because it does not return a value.)
Returns:
true iff the use of the put method should be avoided when updating the front Map, and putAll should be used instead

setFrontPutBlind

public void setFrontPutBlind(boolean fUseFrontPutAll)
Specify whether the front Map is more efficiently updated using putAll.
Parameters:
fUseFrontPutAll - pass true to allow null values; false to disallow

getFrontMapListener

protected MapListener getFrontMapListener()
Get the MapListener for the front map.
Returns:
the MapListener for the front map

setFrontMapListener

protected void setFrontMapListener(MapListener listener)
Specify the MapListener for the front map.

The caller is required to manage all of the thread concurrency issues associated with modifying the listener.

Parameters:
listener - the MapListener for the front map

instantiateFrontMapListener

protected MapListener instantiateFrontMapListener()
Factory pattern: Front Map Listener.
Returns:
a new instance of the listener for the front map

onFrontEvent

protected void onFrontEvent(MapEvent evt)
Either handle an event by turning it over to another thread that is processing the key specified by the event, or take responsibility on this thread for deferring the event and registering its immediate side-effects.

processFrontEvent

protected void processFrontEvent(SimpleOverflowMap.Status status,
                                 MapEvent evt)
Process an event. The Status must already be owned by this thread and in the processing or committing state.
Parameters:
evt - the event to process; may be null

beginKeyProcess

protected SimpleOverflowMap.Status beginKeyProcess(java.lang.Object oKey)
Block until a key is available for processing, and return the Status object for that key. The caller is then expected to perform its processing, during which time events against the Map Entry may occur. Note that those events can occur on threads other than the current thread; when this current thread can no longer handle events from other threads, it must call SimpleOverflowMap.Status.closeProcessing() and then perform its final adjustments to the Status data structure, handling any events that were queued in the meantime on the Status. After completing the processing during this "quiet period" in which all other threads are prevented from accessing this entry or handling events for this entry, then the caller must call endKeyProcess(java.lang.Object, com.tangosol.net.cache.SimpleOverflowMap.Status) passing the Status object returned from this method.
Parameters:
oKey - the key to process
Returns:
the Status object for the specified key

endKeyProcess

protected void endKeyProcess(java.lang.Object oKey,
                             SimpleOverflowMap.Status status)
Finish the processing of a single key.
Parameters:
status - the Status object returned from the call to beginKeyProcess(java.lang.Object)

beginBulkKeyProcess

protected SimpleOverflowMap.Status[] beginBulkKeyProcess(java.lang.Object[] aoKey)
Begin key-level procecessing for any number of keys.
Parameters:
aoKey - an array of zero or more keys; note that this array may be re-ordered by this method
Returns:
an array of Status objects corresponding to the passed keys
See Also:
beginKeyProcess(Object)

endBulkKeyProcess

protected void endBulkKeyProcess(java.lang.Object[] aoKey,
                                 SimpleOverflowMap.Status[] aStatus)
Finish the processing of any number of keys.
Parameters:
aoKey - the same array of keys as were passed to beginBulkKeyProcess(java.lang.Object[])
aStatus - the array of Status objects returned from the call to beginBulkKeyProcess(java.lang.Object[])

beginMapProcess

protected void beginMapProcess()
Block until this thread has exclusive access to perform operations against the OverflowMap.

endMapProcess

protected void endMapProcess()
Release exclusive access for the OverflowMap.

processDeferredEvents

protected void processDeferredEvents()
Process deferred events, if there are any. This implementation processes only the first deferred event that it encounters.

verifyNoNulls

protected static void verifyNoNulls(java.util.Collection collection,
                                    java.lang.String sAssert)
Check the passed collection for nulls, and fail if it contains any.
Parameters:
collection - a Collection
sAssert - the human-readable description of the error if any nulls are found in the passed Collection

putOne

protected static void putOne(java.util.Map map,
                             java.lang.Object oKey,
                             java.lang.Object oValue,
                             boolean fPutBlind)
Helper to put a value into a map using either the put or putAll method.
Parameters:
map - the Map to put into
oKey - the key to put
oValue - the value to put
fPutBlind - true to use the putBlind optimization

warnEventSequence

protected static void warnEventSequence(MapEvent evtOld,
                                        MapEvent evtNew)
Issue a one-time warning that events are being received in an order than cannot be explained by normal operation according to the contracts expected by this OverflowMap.
Parameters:
evtOld - the previous (potentially amalgamated) event
evtNew - the new event

instantiateStatus

protected SimpleOverflowMap.Status instantiateStatus()
Factory method: Instantiate a Status object.
Returns:
a new Status object

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Oracle® Coherence Java API Reference
Release 3.6.1.0

E18814-01


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