net.sf.ehcache.store
Class MemoryStore

java.lang.Object
  net.sf.ehcache.store.MemoryStore

All Implemented Interfaces:

Store

Direct Known Subclasses:

FifoMemoryStore, LfuMemoryStore, LruMemoryStore

public abstract class MemoryStore
extends java.lang.Object
implements Store

An abstract class for the Memory Stores. All Memory store implementations for different policies (e.g: FIFO, LFU, LRU, etc.) should extend this class.

Version:

$Id: MemoryStore.java 608 2008-05-04 03:32:51Z gregluck $

Author:

Surya Suravarapu

Field Summary

protected Ehcache	cache The cache this store is associated with.
protected Store	diskStore The DiskStore associated with this MemoryStore.
protected java.util.Map	map Map where items are stored by key.
protected Status	status status.

Constructor Summary

protected

MemoryStore(Ehcache cache, Store diskStore) Constructs things that all MemoryStores have in common.

Method Summary

boolean	backedUp() Memory stores are never backed up and always return false
protected void	clear() Clears any data structures and places it back to its state when it was first created.
boolean	containsKey(java.lang.Object key) An unsynchronized check to see if a key is in the Store.
static MemoryStore	create(Ehcache cache, Store diskStore) A factory method to create a MemoryStore.
void	dispose() Prepares for shutdown.
protected void	doPut(Element element) Allow specialised actions over adding the element to the map.
protected void	evict(Element element) Evict the Element.
void	expireElements() Expire all elsments.
void	flush() Flush to disk only if the cache is diskPersistent.
Element	get(java.lang.Object key) Gets an item from the cache.
(package private) java.util.Map	getBackingMap() Package local access to the map for testing
java.lang.Object[]	getKeyArray() Gets an Array of the keys for all elements in the memory cache.
Element	getQuiet(java.lang.Object key) Gets an item from the cache, without updating statistics.
int	getSize() Returns the current cache size.
long	getSizeInBytes() Measures the size of the memory store by measuring the serialized size of all elements.
Status	getStatus() Gets the status of the MemoryStore.
protected boolean	isFull() An algorithm to tell if the MemoryStore is at or beyond its carrying capacity.
protected void	notifyExpiry(Element element) Before eviction elements are checked.
void	put(Element element) Puts an item in the cache.
Element	remove(java.lang.Object key) Removes an Element from the store.
void	removeAll() Remove all of the elements from the store.
protected void	spoolAllToDisk() Spools all elements to disk, in preparation for shutdown.
protected void	spoolToDisk(Element element) Puts the element in the DiskStore.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

cache

protected Ehcache cache

The cache this store is associated with.

map

protected java.util.Map map

Map where items are stored by key.

diskStore

protected final Store diskStore

The DiskStore associated with this MemoryStore.

status

protected Status status

status.

Constructor Detail

MemoryStore

protected MemoryStore(Ehcache cache,
                      Store diskStore)

Constructs things that all MemoryStores have in common.

Parameters:

cache -

diskStore -

Method Detail

create

public static MemoryStore create(Ehcache cache,
                                 Store diskStore)

A factory method to create a MemoryStore.

Parameters:

cache -

diskStore -

Returns:

an instance of a MemoryStore, configured with the appropriate eviction policy

put

public final void put(Element element)
               throws CacheException

Puts an item in the cache. Note that this automatically results in LruMemoryStore.SpoolingLinkedHashMap.removeEldestEntry(java.util.Map.Entry) being called.

Specified by:

put in interface Store

Parameters:

element - the element to add

Throws:

CacheException

doPut

protected void doPut(Element element)
              throws CacheException

Allow specialised actions over adding the element to the map.

Parameters:

element -

Throws:

CacheException

get

public final Element get(java.lang.Object key)

Gets an item from the cache.

The last access time in Element is updated.

Specified by:

get in interface Store

Parameters:

key - the cache key

Returns:

the element, or null if there was no match for the key

getQuiet

public final Element getQuiet(java.lang.Object key)

Gets an item from the cache, without updating statistics.

Specified by:

getQuiet in interface Store

Parameters:

key - the cache key

Returns:

the element, or null if there was no match for the key

remove

public final Element remove(java.lang.Object key)

Removes an Element from the store.

Specified by:

remove in interface Store

Parameters:

key - the key of the Element, usually a String

Returns:

the Element if one was found, else null

removeAll

public final void removeAll()
                     throws CacheException

Remove all of the elements from the store.

Specified by:

removeAll in interface Store

Throws:

CacheException

clear

protected final void clear()

Clears any data structures and places it back to its state when it was first created.

dispose

public final void dispose()

Prepares for shutdown.

Specified by:

dispose in interface Store

flush

public final void flush()

Flush to disk only if the cache is diskPersistent.

Specified by:

flush in interface Store

spoolAllToDisk

protected final void spoolAllToDisk()

Spools all elements to disk, in preparation for shutdown.

Relies on being called from a synchronized method

This revised implementation is a little slower but avoids using increased memory during the method.

spoolToDisk

protected void spoolToDisk(Element element)

Puts the element in the DiskStore. Should only be called if Ehcache.isOverflowToDisk() is true

Relies on being called from a synchronized method

Parameters:

element - The Element

getStatus

public final Status getStatus()

Gets the status of the MemoryStore.

Specified by:

getStatus in interface Store

getKeyArray

public final java.lang.Object[] getKeyArray()

Gets an Array of the keys for all elements in the memory cache.

Does not check for expired entries

Specified by:

getKeyArray in interface Store

Returns:

An Object[]

getSize

public final int getSize()

Returns the current cache size.

Specified by:

getSize in interface Store

Returns:

The size value

containsKey

public final boolean containsKey(java.lang.Object key)

An unsynchronized check to see if a key is in the Store. No check is made to see if the Element is expired.

Specified by:

containsKey in interface Store

Parameters:

key - The Element key

Returns:

true if found. If this method return false, it means that an Element with the given key is definitely not in the MemoryStore. If it returns true, there is an Element there. An attempt to get it may return null if the Element has expired.

getSizeInBytes

public final long getSizeInBytes()
                          throws CacheException

Measures the size of the memory store by measuring the serialized size of all elements. If the objects are not Serializable they count as 0.

Warning: This method can be very expensive to run. Allow approximately 1 second per 1MB of entries. Running this method could create liveness problems because the object lock is held for a long period

Returns:

the size, in bytes

Throws:

CacheException

evict

protected final void evict(Element element)
                    throws CacheException

Evict the Element.

Evict means that the Element is:

• if, the store is diskPersistent, the Element is spooled to the DiskStore
• if not, the Element is removed.

Parameters:

element - the Element to be evicted.

Throws:

CacheException

notifyExpiry

protected final void notifyExpiry(Element element)

Before eviction elements are checked.

Parameters:

element -

isFull

protected final boolean isFull()

An algorithm to tell if the MemoryStore is at or beyond its carrying capacity.

expireElements

public void expireElements()

Expire all elsments.

This is a default implementation which does nothing. Expiry on demand is only implemented for disk stores.

Specified by:

expireElements in interface Store

backedUp

public boolean backedUp()

Memory stores are never backed up and always return false

Specified by:

backedUp in interface Store

Returns:

true if the store is backed up.

getBackingMap

java.util.Map getBackingMap()

Package local access to the map for testing