com.bea.p13n.cache
Interface Cache

All Superinterfaces:

CacheDefaults, CacheStats, ReloadableCache

public interface Cache

extends CacheDefaults, CacheStats, ReloadableCache

The main interface for the cache. Provides methods to add, access, and remove entries from a cache.

Keys may be any object, although it is suggested that Strings or lightweight Serializable objects be used. In order to receive notifications to invalidate a particular key in the cache (from other nodes of a cluster or from Admin server), the key must be Serializable (so it can be transmitted between servers). Such keys must also have properly implemented equals() and hashcode() methods.

CAUTION: The cache data structure does not itself provide immutability of its values. In other words, it returns references to its actual objects. It is recommended that those values protect themselves from change unless that change is actually desired - remember these objects will eventually expire from the Cache.

Field Summary

Fields inherited from interface com.bea.p13n.cache.CacheDefaults

DEFAULT_ENABLED, DEFAULT_MAX_ENTRIES, DEFAULT_TTL, MAX_ENTRIES_MAX, TTL_NEVER_EXPIRE

Method Summary

void	clear() Remove all elements from the cache.
boolean	containsKey(Object key) Determines if an entry exists in the cache.
Set	entrySet() Access the values of the key/value pair of the Cache.
Object	get(Object key) Retrieve an entry in the Cache.
int	getMaxEntries() Get the max number of entries the cache can have.
String	getName() Get cache name.
long	getTtl() Get the time-to-live, in milliseconds, of entries for the cache.
boolean	isEnabled() Is the cache enabled?
Set	keySet() Access the keys of the key/value pair of the Cache.
Object	put(Object key, Object value) Put a value into the cache.
Object	put(Object key, Object value, long ttl) Put a value into the cache, with a specific time-to-live.
Object	remove(Object key) Removes a single entry from the Cache if it exists.
void	setEnabled(boolean newEnabled) Set enabled mode of cache.
void	setMaxEntries(int maxEntries) Set the max number of items the cache can have.
void	setTtl(long timeToLive) Set the default time-to-live for all elements in cache.
int	size() Size of the cache.
String	toString() Describes the attributes of the cache.

Methods inherited from interface com.bea.p13n.cache.CacheStats

getHitCount, getHitRate, getMissCount, resetStats

Methods inherited from interface com.bea.p13n.cache.ReloadableCache

getReloader, put, put, reload, setReloader, unsetReloader

Method Detail

clear

public void clear()

Remove all elements from the cache.

containsKey

public boolean containsKey(Object key)

Determines if an entry exists in the cache.

Parameters:

key - The key of a key/value pair to check for existence in the cache.

Returns:

boolean true if the object associated with that key exists in the cache, false otherwise.

entrySet

public Set entrySet()

Access the values of the key/value pair of the Cache. Values that have expired are not included in this set.

Returns:

Set The set of values of the key/value pair of the Cache.

get

public Object get(Object key)

Retrieve an entry in the Cache. Returns null if the entry does not exist or has expired or if the cache is not enabled. Otherwise, it returns the Value associated with the key and moves the entry to the top of the LRU list (making it the most recently used object.

Parameters:

key - The key of a key/value pair to retrieve from the cache.

Returns:

Object the value of the key/value pair asslciated with the key, or null if the entry does not exist or has expired.

getMaxEntries

public int getMaxEntries()

Get the max number of entries the cache can have. The cache uses a LRU strategy, so that it will never contain more than maxEntries entries.

Returns:

the maximum number of entries of the cache

getName

public String getName()

Get cache name. Each cache has a unique name, and is referenced by that name. The CacheFactory maintains a collection of cache objects, and the cache name represents the key in the key/value pair in the collection.

Returns:

The cache name

getTtl

public long getTtl()

Get the time-to-live, in milliseconds, of entries for the cache. Unless specified for each entry individually, the time-to-live is set upon creation of the cache and applies to all entries in the cache.

Returns:

the cache's time-to-live value in milliseconds

isEnabled

public boolean isEnabled()

Is the cache enabled?

Returns:

boolean, true if it is enabled, flase otherwise.

keySet

public Set keySet()

Access the keys of the key/value pair of the Cache. Values that have expired are not included in this set.

Returns:

Set The set of keys in the key/value entries of the cacbe.

put

public Object put(Object key,
                  Object value)

Put a value into the cache.

Neither the key nor the value can be null

Parameters:

key - the key of the entry to create

value - the value to associate with the key

Returns:

Object the previous value for the key

put

public Object put(Object key,
                  Object value,
                  long ttl)

Put a value into the cache, with a specific time-to-live.

Neither the key nor the value can be null

Parameters:

key - the key of the entry to create

value - the value to associate with the key

ttl - time-to-live, in milliseconds, of the object. This ttl overrides the default ttl for the cache, and applies only to this object.

Returns:

Object the previous value for the key

remove

public Object remove(Object key)

Removes a single entry from the Cache if it exists.

Parameters:

key - The key of a key/value pair to remove from the cache.

Returns:

The object that was removed, or null if object did not exist.

setEnabled

public void setEnabled(boolean newEnabled)

Set enabled mode of cache. Disabling the cache will flush the cache and cause fetch, add, and remove to do nothing.

Parameters:

newEnabled - true to enable the cache, false to disable the cache.

setMaxEntries

public void setMaxEntries(int maxEntries)

Set the max number of items the cache can have. Because the cache implements a LRU (least-recently-used) strategy, the maximum allowed value for this is defined in CacheDefaults.MAX_ENTRIES_MAX.

Parameters:

maxEntries - the maximum size of the cache

setTtl

public void setTtl(long timeToLive)

Set the default time-to-live for all elements in cache. Note that using a value of TTL_NEVER_EXPIRE, means elements will never expire.

size

public int size()

Size of the cache. This returns the size of the internal map. This may or may not match the size of the collection returned from the values method. The values method will strip out all expired values.

Returns:

int The number of entries in the cache.

toString

public String toString()

Describes the attributes of the cache.

Returns:

the attributes of the cache.