org.castor.cache.hashbelt
Class AbstractHashbelt

java.lang.Object
  org.castor.cache.AbstractBaseCache
      org.castor.cache.hashbelt.AbstractHashbelt

All Implemented Interfaces:

Cache, java.util.Map

Direct Known Subclasses:

FIFOHashbelt, LRUHashbelt

public abstract class AbstractHashbelt

extends AbstractBaseCache

An abstract, core implementation of the hashbelt functionality; individual implementations will differ on the underlying behavior.

A hashbelt has six important values which get set at initialization:

containers

The number of containers in the conveyor belt. For example: If a box will drop off of the conveyor belt every 30 seconds, and you want a cache that lasts for 5 minutes, you want 5 / 30 = 6 containers on the belt. Every 30 seconds, another, clean container goes on the front of the conveyor belt, and everything in the last belt gets discarded. If not specified 10 containers are used by default.
For systems with fine granularity, you are free to use a large number of containers; but the system is most efficient when the user decides on a "sweet spot" determining both the number of containers to be managed on the whole and the optimal number of buckets in those containers for managing. This is ultimately a performance/accuracy tradeoff with the actual discard-from-cache time being further from the mark as the rotation time goes up. Also the number of objects discarded at once when capacity limit is reached depends upon the number of containers.

capacity

Maximum capacity of the whole cache. If there are, for example, ten containers on the belt and the capacity has been set to 1000, each container will hold a maximum of 1000/10 objects. Therefore if the capacity limit is reached and the last container gets droped from the belt there are up to 100 objects discarted at once. By default the capacity is set to 0 which causes capacity limit to be ignored so the cache can hold an undefined number of objects.

ttl

The maximum time an object lifes in cache. If the are, for example, ten containers and ttl is set to 300 seconds (5 minutes), a new container will be put in front of the belt every 300/10 = 30 seconds while another is dropped at the end at the same time. Due to the granularity of 30 seconds, everything just until 5 minutes 30 seconds will also end up in this box. The default value for ttl is 60 seconds. If ttl is set to 0 which means that objects life in cache for unlimited time and may only discarded by a capacity limit.

monitor

The monitor intervall in minutes when hashbelt cache rports the current number of containers used and objects cached. If set to 0 (default) monitoring is disabled.

container-class

The implementation of org.castor.cache.hashbelt.container.Container interface to be used for all containers of the cache. Castor provides the following 3 implementations of the Container interface.
org.castor.cache.hashbelt.container.FastIteratingContainer
org.castor.cache.hashbelt.container.MapContainer
org.castor.cache.hashbelt.container.WeakReferenceContainer
If not specified the MapContainer will be used as default.

reaper-class

Specific reapers yield different behaviors. The GC reaper, the default, just dumps the contents to the garbage collector. However, custom implementations may want to actually do something when a bucket drops off the end; see the javadocs on other available reapers to find a reaper strategy that meets your behavior requirements. Apart of the default org.castor.cache.hashbelt.reaper.NullReaper we provide 3 abstract implementations of org.castor.cahe.hashbelt.reaper.Reaper interface:
org.castor.cache.hashbelt.reaper.NotifyingReaper
org.castor.cache.hashbelt.reaper.RefreshingReaper
org.castor.cache.hashbelt.reaper.ReinsertingReaper
to be extended by your custom implementation.

Since:

1.0

Version:

$Revision: 7121 $ $Date: 2006-04-25 16:09:10 -0600 (Tue, 25 Apr 2006) $

Author:

Gregory Block, Ralf Joachim

Nested Class Summary

Nested classes inherited from class java.util.Map

java.util.Map.Entry

Field Summary

static int	DEFAULT_CAPACITY Default capacity of cache.
static java.lang.Class	DEFAULT_CONTAINER_CLASS Default container class.
static int	DEFAULT_CONTAINERS Default number of containers for cache.
static int	DEFAULT_MONITOR Default monitor interval of cache in minutes.
static java.lang.Class	DEFAULT_REAPER_CLASS Default reaper class.
static int	DEFAULT_TTL Default ttl of cache in seconds.
static java.lang.String	PARAM_CAPACITY Mapped initialization parameter capacity.
static java.lang.String	PARAM_CONTAINER_CLASS Mapped initialization parameter container-class.
static java.lang.String	PARAM_CONTAINERS Mapped initialization parameter containers.
static java.lang.String	PARAM_MONITOR Mapped initialization parameter monitor.
static java.lang.String	PARAM_REAPER_CLASS Mapped initialization parameter reaper-class.
static java.lang.String	PARAM_TTL Mapped initialization parameter ttl.

Fields inherited from interface org.castor.cache.Cache

DEFAULT_DEBUG, DEFAULT_NAME, DEFAULT_TYPE, PARAM_DEBUG, PARAM_NAME, PARAM_TYPE

Constructor Summary

AbstractHashbelt()

Method Summary

void	clear()
void	close() Life-cycle method to allow custom resource cleanup for a cache implementation.
boolean	containsKey(java.lang.Object key)
boolean	containsValue(java.lang.Object value)
java.util.Set	entrySet()
int	getCapacity() Get real capacity of this cache.
protected java.lang.Object	getObjectFromCache(java.lang.Object key) Get object currently associated with given key from cache.
int	getTTL() Get real ttl of this cache.
void	initialize(java.util.Properties params) Lyfe-cycle method to allow custom initialization of cache implementations.
boolean	isEmpty()
java.util.Set	keySet()
protected org.castor.util.concurrent.ReadWriteLock	lock() Get reference to the ReadWriteLock of this cache instance.
protected java.lang.Object	putObjectIntoCache(java.lang.Object key, java.lang.Object value) Put given value with given key in cache.
protected java.lang.Object	removeObjectFromCache(java.lang.Object key) Remove any available association for given key.
int	size()
java.util.Collection	values()

Methods inherited from class org.castor.cache.AbstractBaseCache

expire, expireAll, getName, invokeMethod, invokeStaticMethod

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.castor.cache.Cache

getType

Methods inherited from interface java.util.Map

equals, get, hashCode, put, putAll, remove

Field Detail

PARAM_CONTAINERS

public static final java.lang.String PARAM_CONTAINERS

Mapped initialization parameter containers.

See Also:

Constant Field Values

PARAM_CONTAINER_CLASS

public static final java.lang.String PARAM_CONTAINER_CLASS

Mapped initialization parameter container-class.

See Also:

Constant Field Values

PARAM_REAPER_CLASS

public static final java.lang.String PARAM_REAPER_CLASS

Mapped initialization parameter reaper-class.

See Also:

Constant Field Values

PARAM_CAPACITY

public static final java.lang.String PARAM_CAPACITY

Mapped initialization parameter capacity.

See Also:

Constant Field Values

PARAM_TTL

public static final java.lang.String PARAM_TTL

Mapped initialization parameter ttl.

See Also:

Constant Field Values

PARAM_MONITOR

public static final java.lang.String PARAM_MONITOR

Mapped initialization parameter monitor.

See Also:

Constant Field Values

DEFAULT_CONTAINERS

public static final int DEFAULT_CONTAINERS

Default number of containers for cache.

See Also:

Constant Field Values

DEFAULT_CONTAINER_CLASS

public static final java.lang.Class DEFAULT_CONTAINER_CLASS

Default container class.

DEFAULT_REAPER_CLASS

public static final java.lang.Class DEFAULT_REAPER_CLASS

Default reaper class.

DEFAULT_CAPACITY

public static final int DEFAULT_CAPACITY

Default capacity of cache.

See Also:

Constant Field Values

DEFAULT_TTL

public static final int DEFAULT_TTL

Default ttl of cache in seconds.

See Also:

Constant Field Values

DEFAULT_MONITOR

public static final int DEFAULT_MONITOR

Default monitor interval of cache in minutes.

See Also:

Constant Field Values

Constructor Detail

AbstractHashbelt

public AbstractHashbelt()

Method Detail

initialize

public final void initialize(java.util.Properties params)
                      throws CacheAcquireException

Lyfe-cycle method to allow custom initialization of cache implementations.

Specified by:

initialize in interface Cache

Overrides:

initialize in class AbstractBaseCache

Throws:

CacheAcquireException

See Also:

Cache.initialize(java.util.Properties)

close

public final void close()

Life-cycle method to allow custom resource cleanup for a cache implementation.

Specified by:

close in interface Cache

Overrides:

close in class AbstractBaseCache

See Also:

Cache.close()

getCapacity

public final int getCapacity()

Get real capacity of this cache.

Returns:

Real capacity of this cache.

getTTL

public final int getTTL()

Get real ttl of this cache.

Returns:

Real ttl of this cache.

size

public final int size()

See Also:

Map.size()

isEmpty

public final boolean isEmpty()

See Also:

Map.isEmpty()

containsKey

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

See Also:

Map.containsKey(java.lang.Object)

containsValue

public final boolean containsValue(java.lang.Object value)

See Also:

Map.containsValue(java.lang.Object)

clear

public final void clear()

See Also:

Map.clear()

keySet

public final java.util.Set keySet()

See Also:

Map.keySet()

values

public final java.util.Collection values()

See Also:

Map.values()

entrySet

public final java.util.Set entrySet()

See Also:

Map.entrySet()

lock

protected final org.castor.util.concurrent.ReadWriteLock lock()

Get reference to the ReadWriteLock of this cache instance.

Returns:

ReadWriteLock to synchronize access to cache.

getObjectFromCache

protected final java.lang.Object getObjectFromCache(java.lang.Object key)

Get object currently associated with given key from cache. Take care to acquire a read or write lock before calling this method and release the lock thereafter.

Parameters:

key - The key to return the associated object for.

Returns:

The object associated with given key.

putObjectIntoCache

protected final java.lang.Object putObjectIntoCache(java.lang.Object key,
                                                    java.lang.Object value)

Put given value with given key in cache. Return the object previously associated with key. Take care to acquire a write lock before calling this method and release the lock thereafter.

Parameters:

key - The key to associate the given value with.

value - The value to associate with given key.

Returns:

The object previously associated with given key. null will be returned if no value has been associated with key.

removeObjectFromCache

protected final java.lang.Object removeObjectFromCache(java.lang.Object key)

Remove any available association for given key. Take care to acquire a write lock before calling this method and release the lock thereafter.

Parameters:

key - The key to remove any previously associate value for.

Returns:

The object previously associated with given key. null will be returned if no value has been associated with key.