net.sf.ehcache

Interface Ehcache

public interface Ehcache extends Cloneable

An interface for Ehcache.

Ehcache is the central interface. Caches have Elements and are managed by the CacheManager. The Cache performs logical actions. It delegates physical implementations to its Stores.

A reference to an EhCache can be obtained through the CacheManager. An Ehcache thus obtained is guaranteed to have status STATUS_ALIVE. This status is checked for any method which throws IllegalStateException and the same thrown if it is not alive. This would normally happen if a call is made after CacheManager is invoked.

Statistics on cache usage are collected and made available through public methods.

Version: $Id: Ehcache.java 191 2006-09-03 22:41:48Z gregluck $

Author: Greg Luck

Method Summary
voidbootstrap()
Bootstrap command.
longcalculateInMemorySize()
Gets the size of the memory store for this cache

Warning: This method can be very expensive to run.

voidclearStatistics()
Resets statistics counters back to 0.
Objectclone()
Clones a cache.
voiddispose()
Flushes all cache items from memory to auxilliary caches and close the auxilliary caches.
voidevictExpiredElements()
Causes all elements stored in the Cache to be synchronously checked for expiry, and if expired, evicted.
voidflush()
Flushes all cache items from memory to the disk store, and from the DiskStore to disk.
Elementget(Serializable key)
Gets an element from the cache.
Elementget(Object key)
Gets an element from the cache.
BootstrapCacheLoadergetBootstrapCacheLoader()
Accessor for the BootstrapCacheLoader associated with this cache.
RegisteredEventListenersgetCacheEventNotificationService()
Use this to access the service in order to register and unregister listeners
CacheManagergetCacheManager()
Gets the CacheManager managing this cache.
longgetDiskExpiryThreadIntervalSeconds()
intgetDiskStoreHitCount()
Number of times a requested item was found in the Disk Store.
intgetDiskStoreSize()
Returns the number of elements in the disk store.
StringgetGuid()
The GUID for this cache instance can be used to determine whether two cache instance references are pointing to the same cache.
intgetHitCount()
The number of times a requested item was found in the cache.
ListgetKeys()
Returns a list of all elements in the cache, whether or not they are expired.
ListgetKeysNoDuplicateCheck()
Returns a list of all elements in the cache, whether or not they are expired.
ListgetKeysWithExpiryCheck()
Returns a list of all elements in the cache.
intgetMaxElementsInMemory()
Gets the maximum number of elements to hold in memory.
MemoryStoreEvictionPolicygetMemoryStoreEvictionPolicy()
The policy used to evict elements from the MemoryStore.
intgetMemoryStoreHitCount()
Number of times a requested item was found in the Memory Store.
longgetMemoryStoreSize()
Returns the number of elements in the memory store.
intgetMissCountExpired()
Number of times a requested element was found but was expired.
intgetMissCountNotFound()
Number of times a requested element was not found in the cache.
StringgetName()
Gets the cache name.
ElementgetQuiet(Serializable key)
Gets an element from the cache, without updating Element statistics.
ElementgetQuiet(Object key)
Gets an element from the cache, without updating Element statistics.
intgetSize()
Gets the size of the cache.
StatisticsgetStatistics()
Gets an immutable Statistics object representing the Cache statistics at the time.
intgetStatisticsAccuracy()
Accurately measuring statistics can be expensive.
StatusgetStatus()
Gets the status attribute of the Cache.
longgetTimeToIdleSeconds()
Gets timeToIdleSeconds.
longgetTimeToLiveSeconds()
Gets timeToLiveSeconds.
voidinitialise()
Newly created caches do not have a MemoryStore or a DiskStore.
booleanisDiskPersistent()
booleanisElementInMemory(Serializable key)
Whether an Element is stored in the cache in Memory, indicating a very low cost of retrieval.
booleanisElementInMemory(Object key)
Whether an Element is stored in the cache in Memory, indicating a very low cost of retrieval.
booleanisElementOnDisk(Serializable key)
Whether an Element is stored in the cache on Disk, indicating a higher cost of retrieval.
booleanisElementOnDisk(Object key)
Whether an Element is stored in the cache on Disk, indicating a higher cost of retrieval.
booleanisEternal()
Are elements eternal.
booleanisExpired(Element element)
Checks whether this cache element has expired.
booleanisKeyInCache(Object key)
An inexpensive check to see if the key exists in the cache.
booleanisOverflowToDisk()
Does the overflow go to disk.
booleanisValueInCache(Object value)
An extremely expensive check to see if the value exists in the cache.
voidput(Element element)
Put an element in the cache.
voidput(Element element, boolean doNotNotifyCacheReplicators)
Put an element in the cache.
voidputQuiet(Element element)
Put an element in the cache, without updating statistics, or updating listeners.
booleanremove(Serializable key)
Removes an Element from the Cache.
booleanremove(Object key)
Removes an Element from the Cache.
booleanremove(Serializable key, boolean doNotNotifyCacheReplicators)
Removes an Element from the Cache.
booleanremove(Object key, boolean doNotNotifyCacheReplicators)
Removes an Element from the Cache.
voidremoveAll()
Removes all cached items.
voidremoveAll(boolean doNotNotifyCacheReplicators)
Removes all cached items.
booleanremoveQuiet(Serializable key)
Removes an Element from the Cache, without notifying listeners.
booleanremoveQuiet(Object key)
Removes an Element from the Cache, without notifying listeners.
voidsetBootstrapCacheLoader(BootstrapCacheLoader bootstrapCacheLoader)
Sets the bootstrap cache loader.
voidsetCacheManager(CacheManager cacheManager)
Sets the CacheManager
voidsetDiskStorePath(String diskStorePath)
DiskStore paths can conflict between CacheManager instances.
voidsetName(String name)
Sets the cache name which will name.
voidsetStatisticsAccuracy(int statisticsAccuracy)
Sets the statistics accuracy.
StringtoString()
Returns a String representation of Cache.

Method Detail

bootstrap

public void bootstrap()
Bootstrap command. This must be called after the Cache is intialised, during CacheManager initialisation. If loads are synchronous, they will complete before the CacheManager initialise completes, otherwise they will happen in the background.

calculateInMemorySize

public long calculateInMemorySize()
Gets the size of the memory store for this cache

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 approximate size of the memory store in bytes

Throws: IllegalStateException

clearStatistics

public void clearStatistics()
Resets statistics counters back to 0.

clone

public Object clone()
Clones a cache. This is only legal if the cache has not been initialized. At that point only primitives have been set and no LruMemoryStore or DiskStore has been created.

A new, empty, RegisteredEventListeners is created on clone.

Returns: an object of type Cache

Throws: CloneNotSupportedException

dispose

public void dispose()
Flushes all cache items from memory to auxilliary caches and close the auxilliary caches.

Should be invoked only by CacheManager.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

evictExpiredElements

public void evictExpiredElements()
Causes all elements stored in the Cache to be synchronously checked for expiry, and if expired, evicted.

flush

public void flush()
Flushes all cache items from memory to the disk store, and from the DiskStore to disk.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

get

public Element get(Serializable key)
Gets an element from the cache. Updates Element Statistics

Note that the Element's lastAccessTime is always the time of this get. Use getQuiet to peak into the Element to see its last access time with get

Parameters: key a serializable value

Returns: the element, or null, if it does not exist.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

See Also: Ehcache

get

public Element get(Object key)
Gets an element from the cache. Updates Element Statistics

Note that the Element's lastAccessTime is always the time of this get. Use getQuiet to peak into the Element to see its last access time with get

Parameters: key an Object value

Returns: the element, or null, if it does not exist.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

Since: 1.2

See Also: Ehcache

getBootstrapCacheLoader

public BootstrapCacheLoader getBootstrapCacheLoader()
Accessor for the BootstrapCacheLoader associated with this cache. For testing purposes.

Returns: the BootstrapCacheLoader to use

getCacheEventNotificationService

public RegisteredEventListeners getCacheEventNotificationService()
Use this to access the service in order to register and unregister listeners

Returns: the RegisteredEventListeners instance for this cache.

getCacheManager

public CacheManager getCacheManager()
Gets the CacheManager managing this cache. For a newly created cache this will be null until it has been added to a CacheManager.

Returns: the manager or null if there is none

getDiskExpiryThreadIntervalSeconds

public long getDiskExpiryThreadIntervalSeconds()

Returns: the interval between runs of the expiry thread, where it checks the disk store for expired elements. It is not the the timeToLiveSeconds.

getDiskStoreHitCount

public int getDiskStoreHitCount()
Number of times a requested item was found in the Disk Store.

getDiskStoreSize

public int getDiskStoreSize()
Returns the number of elements in the disk store.

Returns: the number of elements in the disk store.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

getGuid

public String getGuid()
The GUID for this cache instance can be used to determine whether two cache instance references are pointing to the same cache.

Returns: the globally unique identifier for this cache instance. This is guaranteed to be unique.

Since: 1.2

getHitCount

public int getHitCount()
The number of times a requested item was found in the cache.

Returns: the number of times a requested item was found in the cache

getKeys

public List getKeys()
Returns a list of all elements in the cache, whether or not they are expired.

The returned keys are unique and can be considered a set.

The List returned is not live. It is a copy.

The time taken is O(n). On a single cpu 1.8Ghz P4, approximately 8ms is required for each 1000 entries.

Returns: a list of Object keys

Throws: IllegalStateException if the cache is not STATUS_ALIVE

getKeysNoDuplicateCheck

public List getKeysNoDuplicateCheck()
Returns a list of all elements in the cache, whether or not they are expired.

The returned keys are not unique and may contain duplicates. If the cache is only using the memory store, the list will be unique. If the disk store is being used as well, it will likely contain duplicates, because of the internal store design.

The List returned is not live. It is a copy.

The time taken is O(log n). On a single cpu 1.8Ghz P4, approximately 6ms is required for 1000 entries and 36 for 50000.

This is the fastest getKeys method

Returns: a list of Object keys

Throws: IllegalStateException if the cache is not STATUS_ALIVE

getKeysWithExpiryCheck

public List getKeysWithExpiryCheck()
Returns a list of all elements in the cache. Only keys of non-expired elements are returned.

The returned keys are unique and can be considered a set.

The List returned is not live. It is a copy.

The time taken is O(n), where n is the number of elements in the cache. On a 1.8Ghz P4, the time taken is approximately 200ms per 1000 entries. This method is not synchronized, because it relies on a non-live list returned from getKeys , which is synchronised, and which takes 8ms per 1000 entries. This way cache liveness is preserved, even if this method is very slow to return.

Consider whether your usage requires checking for expired keys. Because this method takes so long, depending on cache settings, the list could be quite out of date by the time you get it.

Returns: a list of Object keys

Throws: IllegalStateException if the cache is not STATUS_ALIVE

getMaxElementsInMemory

public int getMaxElementsInMemory()
Gets the maximum number of elements to hold in memory.

getMemoryStoreEvictionPolicy

public MemoryStoreEvictionPolicy getMemoryStoreEvictionPolicy()
The policy used to evict elements from the MemoryStore. This can be one of:
  1. LRU - least recently used
  2. LFU - least frequently used
  3. FIFO - first in first out, the oldest element by creation time
The default value is LRU

Since: 1.2

getMemoryStoreHitCount

public int getMemoryStoreHitCount()
Number of times a requested item was found in the Memory Store.

Returns: Number of times a requested item was found in the Memory Store.

getMemoryStoreSize

public long getMemoryStoreSize()
Returns the number of elements in the memory store.

Returns: the number of elements in the memory store

Throws: IllegalStateException if the cache is not STATUS_ALIVE

getMissCountExpired

public int getMissCountExpired()
Number of times a requested element was found but was expired.

getMissCountNotFound

public int getMissCountNotFound()
Number of times a requested element was not found in the cache. This may be because it expired, in which case this will also be recorded in Ehcache, or because it was simply not there.

getName

public String getName()
Gets the cache name.

getQuiet

public Element getQuiet(Serializable key)
Gets an element from the cache, without updating Element statistics. Cache statistics are still updated.

Parameters: key a serializable value

Returns: the element, or null, if it does not exist.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

See Also: Ehcache

getQuiet

public Element getQuiet(Object key)
Gets an element from the cache, without updating Element statistics. Cache statistics are also not updated.

Parameters: key a serializable value

Returns: the element, or null, if it does not exist.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

Since: 1.2

See Also: Ehcache

getSize

public int getSize()
Gets the size of the cache. This is a subtle concept. See below.

The size is the number of Elements in the MemoryStore plus the number of Elements in the DiskStore.

This number is the actual number of elements, including expired elements that have not been removed.

Expired elements are removed from the the memory store when getting an expired element, or when attempting to spool an expired element to disk.

Expired elements are removed from the disk store when getting an expired element, or when the expiry thread runs, which is once every five minutes.

To get an exact size, which would exclude expired elements, use getKeysWithExpiryCheck.size(), although see that method for the approximate time that would take.

To get a very fast result, use getKeysNoDuplicateCheck.size(). If the disk store is being used, there will be some duplicates.

Returns: The size value

Throws: IllegalStateException if the cache is not STATUS_ALIVE

getStatistics

public Statistics getStatistics()
Gets an immutable Statistics object representing the Cache statistics at the time. How the statistics are calculated depends on the statistics accuracy setting. The only aspect of statistics sensitive to the accuracy setting is object size. How that is calculated is discussed below.

Best Effort Size

This result is returned when the statistics accuracy setting is STATISTICS_ACCURACY_BEST_EFFORT.

The size is the number of Elements in the MemoryStore plus the number of Elements in the DiskStore.

This number is the actual number of elements, including expired elements that have not been removed. Any duplicates between stores are accounted for.

Expired elements are removed from the the memory store when getting an expired element, or when attempting to spool an expired element to disk.

Expired elements are removed from the disk store when getting an expired element, or when the expiry thread runs, which is once every five minutes.

Guaranteed Accuracy Size

This result is returned when the statistics accuracy setting is STATISTICS_ACCURACY_GUARANTEED.

This method accounts for elements which might be expired or duplicated between stores. It take approximately 200ms per 1000 elements to execute.

Fast but non-accurate Size

This result is returned when the statistics accuracy setting is STATISTICS_ACCURACY_NONE.

The number given may contain expired elements. In addition if the DiskStore is used it may contain some double counting of elements. It takes 6ms for 1000 elements to execute. Time to execute is O(log n). 50,000 elements take 36ms.

Returns: the number of elements in the ehcache, with a varying degree of accuracy, depending on accuracy setting.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

getStatisticsAccuracy

public int getStatisticsAccuracy()
Accurately measuring statistics can be expensive. Returns the current accuracy setting.

Returns: one of STATISTICS_ACCURACY_BEST_EFFORT, STATISTICS_ACCURACY_GUARANTEED, STATISTICS_ACCURACY_NONE

getStatus

public Status getStatus()
Gets the status attribute of the Cache.

Returns: The status value from the Status enum class

getTimeToIdleSeconds

public long getTimeToIdleSeconds()
Gets timeToIdleSeconds.

getTimeToLiveSeconds

public long getTimeToLiveSeconds()
Gets timeToLiveSeconds.

initialise

public void initialise()
Newly created caches do not have a MemoryStore or a DiskStore.

This method creates those and makes the cache ready to accept elements

isDiskPersistent

public boolean isDiskPersistent()

Returns: true if the cache overflows to disk and the disk is persistent between restarts

isElementInMemory

public boolean isElementInMemory(Serializable key)
Whether an Element is stored in the cache in Memory, indicating a very low cost of retrieval.

Returns: true if an element matching the key is found in memory

isElementInMemory

public boolean isElementInMemory(Object key)
Whether an Element is stored in the cache in Memory, indicating a very low cost of retrieval.

Returns: true if an element matching the key is found in memory

Since: 1.2

isElementOnDisk

public boolean isElementOnDisk(Serializable key)
Whether an Element is stored in the cache on Disk, indicating a higher cost of retrieval.

Returns: true if an element matching the key is found in the diskStore

isElementOnDisk

public boolean isElementOnDisk(Object key)
Whether an Element is stored in the cache on Disk, indicating a higher cost of retrieval.

Returns: true if an element matching the key is found in the diskStore

Since: 1.2

isEternal

public boolean isEternal()
Are elements eternal.

isExpired

public boolean isExpired(Element element)
Checks whether this cache element has expired.

The element is expired if:

  1. the idle time is non-zero and has elapsed, unless the cache is eternal; or
  2. the time to live is non-zero and has elapsed, unless the cache is eternal; or
  3. the value of the element is null.

Returns: true if it has expired

Throws: IllegalStateException if the cache is not STATUS_ALIVE NullPointerException if the element is null

isKeyInCache

public boolean isKeyInCache(Object key)
An inexpensive check to see if the key exists in the cache.

Parameters: key the key to check for

Returns: true if an Element matching the key is found in the cache. No assertions are made about the state of the Element.

isOverflowToDisk

public boolean isOverflowToDisk()
Does the overflow go to disk.

isValueInCache

public boolean isValueInCache(Object value)
An extremely expensive check to see if the value exists in the cache.

Parameters: value to check for

Returns: true if an Element matching the key is found in the cache. No assertions are made about the state of the Element.

put

public void put(Element element)
Put an element in the cache.

Resets the access statistics on the element, which would be the case if it has previously been gotten from a cache, and is now being put back.

Also notifies the CacheEventListener that:

Parameters: element An object. If Serializable it can fully participate in replication and the DiskStore.

Throws: IllegalStateException if the cache is not STATUS_ALIVE IllegalArgumentException if the element is null CacheException

put

public void put(Element element, boolean doNotNotifyCacheReplicators)
Put an element in the cache.

Resets the access statistics on the element, which would be the case if it has previously been gotten from a cache, and is now being put back.

Also notifies the CacheEventListener that:

Parameters: element An object. If Serializable it can fully participate in replication and the DiskStore. doNotNotifyCacheReplicators whether the put is coming from a doNotNotifyCacheReplicators cache peer, in which case this put should not initiate a further notification to doNotNotifyCacheReplicators cache peers

Throws: IllegalStateException if the cache is not STATUS_ALIVE IllegalArgumentException if the element is null

putQuiet

public void putQuiet(Element element)
Put an element in the cache, without updating statistics, or updating listeners. This is meant to be used in conjunction with Ehcache

Parameters: element An object. If Serializable it can fully participate in replication and the DiskStore.

Throws: IllegalStateException if the cache is not STATUS_ALIVE IllegalArgumentException if the element is null

remove

public boolean remove(Serializable key)
Removes an Element from the Cache. This also removes it from any stores it may be in.

Also notifies the CacheEventListener after the element was removed, but only if an Element with the key actually existed.

Parameters: key

Returns: true if the element was removed, false if it was not found in the cache

Throws: IllegalStateException if the cache is not STATUS_ALIVE

remove

public boolean remove(Object key)
Removes an Element from the Cache. This also removes it from any stores it may be in.

Also notifies the CacheEventListener after the element was removed, but only if an Element with the key actually existed.

Parameters: key

Returns: true if the element was removed, false if it was not found in the cache

Throws: IllegalStateException if the cache is not STATUS_ALIVE

Since: 1.2

remove

public boolean remove(Serializable key, boolean doNotNotifyCacheReplicators)
Removes an Element from the Cache. This also removes it from any stores it may be in.

Also notifies the CacheEventListener after the element was removed, but only if an Element with the key actually existed.

Parameters: key doNotNotifyCacheReplicators whether the put is coming from a doNotNotifyCacheReplicators cache peer, in which case this put should not initiate a further notification to doNotNotifyCacheReplicators cache peers

Returns: true if the element was removed, false if it was not found in the cache

Throws: IllegalStateException if the cache is not STATUS_ALIVE

UNKNOWN: SameParameterValue

remove

public boolean remove(Object key, boolean doNotNotifyCacheReplicators)
Removes an Element from the Cache. This also removes it from any stores it may be in.

Also notifies the CacheEventListener after the element was removed, but only if an Element with the key actually existed.

Parameters: key doNotNotifyCacheReplicators whether the put is coming from a doNotNotifyCacheReplicators cache peer, in which case this put should not initiate a further notification to doNotNotifyCacheReplicators cache peers

Returns: true if the element was removed, false if it was not found in the cache

Throws: IllegalStateException if the cache is not STATUS_ALIVE

removeAll

public void removeAll()
Removes all cached items.

Throws: IllegalStateException if the cache is not STATUS_ALIVE

removeAll

public void removeAll(boolean doNotNotifyCacheReplicators)
Removes all cached items.

Parameters: doNotNotifyCacheReplicators whether the put is coming from a doNotNotifyCacheReplicators cache peer, in which case this put should not initiate a further notification to doNotNotifyCacheReplicators cache peers

Throws: IllegalStateException if the cache is not STATUS_ALIVE

removeQuiet

public boolean removeQuiet(Serializable key)
Removes an Element from the Cache, without notifying listeners. This also removes it from any stores it may be in.

Parameters: key

Returns: true if the element was removed, false if it was not found in the cache

Throws: IllegalStateException if the cache is not STATUS_ALIVE

removeQuiet

public boolean removeQuiet(Object key)
Removes an Element from the Cache, without notifying listeners. This also removes it from any stores it may be in.

Parameters: key

Returns: true if the element was removed, false if it was not found in the cache

Throws: IllegalStateException if the cache is not STATUS_ALIVE

Since: 1.2

setBootstrapCacheLoader

public void setBootstrapCacheLoader(BootstrapCacheLoader bootstrapCacheLoader)
Sets the bootstrap cache loader.

Parameters: bootstrapCacheLoader the loader to be used

Throws: CacheException if this method is called after the cache is initialized

setCacheManager

public void setCacheManager(CacheManager cacheManager)
Sets the CacheManager

Parameters: cacheManager the CacheManager for this cache to use.

setDiskStorePath

public void setDiskStorePath(String diskStorePath)
DiskStore paths can conflict between CacheManager instances. This method allows the path to be changed.

Parameters: diskStorePath the new path to be used.

Throws: CacheException if this method is called after the cache is initialized

setName

public void setName(String name)
Sets the cache name which will name.

Parameters: name the name of the cache. Should not be null.

setStatisticsAccuracy

public void setStatisticsAccuracy(int statisticsAccuracy)
Sets the statistics accuracy.

Parameters: statisticsAccuracy one of STATISTICS_ACCURACY_BEST_EFFORT, STATISTICS_ACCURACY_GUARANTEED, STATISTICS_ACCURACY_NONE

toString

public String toString()
Returns a String representation of Cache.