Package org.apache.fulcrum.cache.impl

Class DefaultGlobalCacheService

java.lang.Object

org.apache.avalon.framework.logger.AbstractLogEnabled

org.apache.fulcrum.cache.impl.DefaultGlobalCacheService

All Implemented Interfaces:

Runnable, org.apache.avalon.framework.activity.Disposable, org.apache.avalon.framework.activity.Initializable, org.apache.avalon.framework.configuration.Configurable, org.apache.avalon.framework.logger.LogEnabled, org.apache.avalon.framework.thread.ThreadSafe, GlobalCacheService

public class DefaultGlobalCacheService
extends org.apache.avalon.framework.logger.AbstractLogEnabled
implements GlobalCacheService, Runnable, org.apache.avalon.framework.configuration.Configurable, org.apache.avalon.framework.activity.Initializable, org.apache.avalon.framework.activity.Disposable, org.apache.avalon.framework.thread.ThreadSafe

This Service functions as a Global Cache. A global cache is a good place to store items that you may need to access often but don't necessarily need (or want) to fetch from the database everytime. A good example would be a look up table of States that you store in a database and use throughout your application. Since information about States doesn't change very often, you could store this information in the Global Cache and decrease the overhead of hitting the database everytime you need State information.

Version:

$Id$

Author:

Dave Bryson, Jon S. Stevens, John Thorhauer, Henning P. Schmiedehausen, Eric Pugh, Peter CourefreshableCachedObjectux

Field Summary

Fields

Modifier and Type	Field	Description
protected ConcurrentHashMap<String,CachedObject<?>>	cache	The cache.
static String	CACHE_CHECK_FREQUENCY	The property for the Cache check frequency
static long	DEFAULT_CACHE_CHECK_FREQUENCY	Cache check frequency in Millis (1000 Millis = 1 second).
static int	DEFAULT_INITIAL_CACHE_SIZE	Initial size of hash table Value must be > 0.
static String	INITIAL_CACHE_SIZE	The property for the InitalCacheSize

Fields inherited from interface org.apache.fulcrum.cache.GlobalCacheService

ROLE

Constructor Summary

Constructors

Constructor	Description
DefaultGlobalCacheService()

Method Summary

Modifier and Type	Method	Description
<T> void	addObject(String objectId, CachedObject<T> object)	Adds an object to the cache.
void	clearCache()	Iterate through the cache and remove or refresh stale objects.
void	configure(org.apache.avalon.framework.configuration.Configuration conf)	Avalon component lifecycle method
void	dispose()	Avalon component lifecycle method
void	flushCache()	Flush the cache of all objects.
long	getCacheCheckFrequency()	Get the Cache Check Frequency in milliseconds
List<CachedObject<?>>	getCachedObjects()	Returns a copy of the non-expired CachedObjects in the cache as a list.
int	getCacheSize()	Returns the current size of the cache.
List<String>	getKeys()	Returns a copy of keys to objects in the cache as a list.
int	getNumberOfObjects()	Returns the number of objects currently stored in the cache
<T> CachedObject<T>	getObject(String objectId)	Returns an item from the cache. /** Returns an item from the cache.
void	initialize()	Avalon component lifecycle method
void	removeObject(String objectId)	Removes an object from the cache.
void	run()	Circle through the cache and remove stale objects.

Methods inherited from class org.apache.avalon.framework.logger.AbstractLogEnabled

enableLogging, getLogger, setupLogger, setupLogger, setupLogger

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_INITIAL_CACHE_SIZE

public static final int DEFAULT_INITIAL_CACHE_SIZE

Initial size of hash table Value must be > 0. Default = 20

See Also:

Constant Field Values

INITIAL_CACHE_SIZE

public static final String INITIAL_CACHE_SIZE

The property for the InitalCacheSize

See Also:

Constant Field Values

CACHE_CHECK_FREQUENCY

public static final String CACHE_CHECK_FREQUENCY

The property for the Cache check frequency

See Also:

Constant Field Values

DEFAULT_CACHE_CHECK_FREQUENCY

public static final long DEFAULT_CACHE_CHECK_FREQUENCY

Cache check frequency in Millis (1000 Millis = 1 second). Value must be > 0. Default = 5 seconds

See Also:

Constant Field Values

cache

protected transient ConcurrentHashMap<String,CachedObject<?>> cache

The cache.

Constructor Detail

DefaultGlobalCacheService

public DefaultGlobalCacheService()

Method Detail

getCacheCheckFrequency

public long getCacheCheckFrequency()

Get the Cache Check Frequency in milliseconds

Returns:

the time between two cache check runs in milliseconds

getObject

public <T> CachedObject<T> getObject(String objectId)
                              throws ObjectExpiredException

Returns an item from the cache. /** Returns an item from the cache. RefreshableCachedObject will be refreshed if it is expired and not untouched.

Specified by:

getObject in interface GlobalCacheService

Type Parameters:

T - type of object to return

Parameters:

objectId - The key of the stored object.

Returns:

The object from the cache.

Throws:

ObjectExpiredException - when either the object is not in the cache or it has expired.

addObject

public <T> void addObject(String objectId,
                          CachedObject<T> object)

Adds an object to the cache.

Specified by:

addObject in interface GlobalCacheService

Type Parameters:

T - type of object to add

Parameters:

objectId - The key to store the object by.

object - The object to cache.

removeObject

public void removeObject(String objectId)

Removes an object from the cache.

Specified by:

removeObject in interface GlobalCacheService

Parameters:

objectId - The String id for the object.

getKeys

public List<String> getKeys()

Returns a copy of keys to objects in the cache as a list. Note that keys to expired objects are not returned.

Specified by:

getKeys in interface GlobalCacheService

Returns:

A List of String's representing the keys to objects in the cache.

getCachedObjects

public List<CachedObject<?>> getCachedObjects()

Returns a copy of the non-expired CachedObjects in the cache as a list.

Specified by:

getCachedObjects in interface GlobalCacheService

Returns:

A List of CachedObject objects held in the cache

run

public void run()

Circle through the cache and remove stale objects. Frequency is determined by the cacheCheckFrequency property.

Specified by:

run in interface Runnable

clearCache

public void clearCache()

Iterate through the cache and remove or refresh stale objects.

getNumberOfObjects

public int getNumberOfObjects()

Returns the number of objects currently stored in the cache

Specified by:

getNumberOfObjects in interface GlobalCacheService

Returns:

int number of object in the cache

getCacheSize

public int getCacheSize()
                 throws IOException

Returns the current size of the cache.

Specified by:

getCacheSize in interface GlobalCacheService

Returns:

int representing current cache size in number of bytes

Throws:

IOException - if unable to return cache size

flushCache

public void flushCache()

Flush the cache of all objects.

Specified by:

flushCache in interface GlobalCacheService

configure

public void configure(org.apache.avalon.framework.configuration.Configuration conf)
               throws org.apache.avalon.framework.configuration.ConfigurationException

Avalon component lifecycle method

Specified by:

configure in interface org.apache.avalon.framework.configuration.Configurable

Throws:

org.apache.avalon.framework.configuration.ConfigurationException

initialize

public void initialize()
                throws Exception

Avalon component lifecycle method

Specified by:

initialize in interface org.apache.avalon.framework.activity.Initializable

Throws:

Exception

dispose

public void dispose()

Avalon component lifecycle method

Specified by:

dispose in interface org.apache.avalon.framework.activity.Disposable