org.jboss.util

Class TimedCachePolicy

java.lang.Object

java.util.TimerTask

org.jboss.util.TimedCachePolicy

All Implemented Interfaces:

java.lang.Runnable, CachePolicy

public class TimedCachePolicy
extends java.util.TimerTask
implements CachePolicy

An implementation of a timed cache. This is a cache whose entries have a limited lifetime with the ability to refresh their lifetime. The entries managed by the cache implement the TimedCachePolicy.TimedEntry interface. If an object inserted into the cache does not implement this interface, it will be wrapped in a DefaultTimedEntry and will expire without the possibility of refresh after getDefaultLifetime() seconds. This is a lazy cache policy in that objects are not checked for expiration until they are accessed.

Version:

$Revision$

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	TimedCachePolicy.DefaultTimedEntry The default implementation of TimedEntry used to wrap non-TimedEntry objects inserted into the cache.
private class	TimedCachePolicy.ResolutionTimer
static interface	TimedCachePolicy.TimedEntry The interface that cache entries support.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	defaultLifetime The lifetime in seconds to use for objects inserted that do not implement the TimedEntry interface.
protected java.util.Map	entryMap The map of cached TimedEntry objects.
private static org.jboss.logging.Logger	log
protected long	now The caches notion of the current time
protected int	resolution The resolution in seconds of the cach current time
protected static java.util.Timer	resolutionTimer
protected TimedCachePolicy.ResolutionTimer	theTimer
protected boolean	threadSafe A flag indicating if entryMap should be synchronized
static java.lang.String	TIMER_CLASSLOADER_CONTEXT Value for TIMER_CLASSLOADER_PROPERTY indicating the thread context classloader in effect when this class is loaded should be used.
static java.lang.String	TIMER_CLASSLOADER_CURRENT Value for TIMER_CLASSLOADER_PROPERTY indicating the classloader that loaded this class should be used.
static java.lang.String	TIMER_CLASSLOADER_PROPERTY Name of system property that this class consults to determine what classloader to assign to its static Timer's thread.
static java.lang.String	TIMER_CLASSLOADER_SYSTEM Value for TIMER_CLASSLOADER_PROPERTY indicating the system classloader should be used.

Constructor Summary

Constructors

Constructor and Description
TimedCachePolicy() Creates a new TimedCachePolicy with a default entry lifetime of 30 mins that does not synchronized access to its policy store and uses a 60 second resolution.
TimedCachePolicy(int defaultLifetime) Creates a new TimedCachePolicy with the given default entry lifetime that does not synchronized access to its policy store and uses a 60 second resolution.
TimedCachePolicy(int defaultLifetime, boolean threadSafe, int resolution) Creates a new TimedCachePolicy with the given default entry lifetime that does/does not synchronized access to its policy store depending on the value of threadSafe.

Method Summary

Modifier and Type	Method and Description
void	create() Initializes the cache for use.
long	currentTimeMillis() Get the cache time.
void	destroy() Clears the cache of all entries.
void	flush() Remove all entries from the cache.
java.lang.Object	get(java.lang.Object key) Get the cache value for key if it has not expired.
int	getDefaultLifetime() Get the default lifetime of cache entries.
int	getResolution() Get the frequency of the current time snapshot.
java.util.List	getValidKeys() Get the list of keys for entries that are not expired.
void	insert(java.lang.Object key, java.lang.Object value) Insert a value into the cache.
java.lang.Object	peek(java.lang.Object key) Get the cache value for key.
TimedCachePolicy.TimedEntry	peekEntry(java.lang.Object key) Get the raw TimedEntry for key without performing any expiration check.
void	remove(java.lang.Object key) Remove the entry associated with key and call destroy on the entry if found.
void	run() The TimerTask run method.
void	setDefaultLifetime(int defaultLifetime) Set the default lifetime of cache entries for new values added to the cache.
void	setResolution(int resolution) Set the cache timer resolution
int	size()
void	start() Schedules this with the class resolutionTimer Timer object for execution every resolution seconds.
void	stop() Stop cancels the resolution timer and flush()es the cache.

Methods inherited from class java.util.TimerTask

cancel, scheduledExecutionTime

Methods inherited from class java.lang.Object

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

Field Detail

TIMER_CLASSLOADER_PROPERTY

public static final java.lang.String TIMER_CLASSLOADER_PROPERTY

Name of system property that this class consults to determine what classloader to assign to its static Timer's thread.

See Also:

Constant Field Values

TIMER_CLASSLOADER_SYSTEM

public static final java.lang.String TIMER_CLASSLOADER_SYSTEM

Value for TIMER_CLASSLOADER_PROPERTY indicating the system classloader should be used. This is the default value if the system property is not set.

See Also:

Constant Field Values

TIMER_CLASSLOADER_CURRENT

public static final java.lang.String TIMER_CLASSLOADER_CURRENT

Value for TIMER_CLASSLOADER_PROPERTY indicating the classloader that loaded this class should be used.

See Also:

Constant Field Values

TIMER_CLASSLOADER_CONTEXT

public static final java.lang.String TIMER_CLASSLOADER_CONTEXT

Value for TIMER_CLASSLOADER_PROPERTY indicating the thread context classloader in effect when this class is loaded should be used.

See Also:

Constant Field Values

log

private static final org.jboss.logging.Logger log

resolutionTimer

protected static java.util.Timer resolutionTimer

entryMap

protected java.util.Map entryMap

The map of cached TimedEntry objects.

defaultLifetime

protected int defaultLifetime

The lifetime in seconds to use for objects inserted that do not implement the TimedEntry interface.

threadSafe

protected boolean threadSafe

A flag indicating if entryMap should be synchronized

now

protected long now

The caches notion of the current time

resolution

protected int resolution

The resolution in seconds of the cach current time

theTimer

protected TimedCachePolicy.ResolutionTimer theTimer

Constructor Detail

TimedCachePolicy

public TimedCachePolicy()

Creates a new TimedCachePolicy with a default entry lifetime of 30 mins that does not synchronized access to its policy store and uses a 60 second resolution.

TimedCachePolicy

public TimedCachePolicy(int defaultLifetime)

Creates a new TimedCachePolicy with the given default entry lifetime that does not synchronized access to its policy store and uses a 60 second resolution.

Parameters:

defaultLifetime -

TimedCachePolicy

public TimedCachePolicy(int defaultLifetime,
                        boolean threadSafe,
                        int resolution)

Creates a new TimedCachePolicy with the given default entry lifetime that does/does not synchronized access to its policy store depending on the value of threadSafe.

Parameters:

defaultLifetime - - the lifetime in seconds to use for objects inserted that do not implement the TimedEntry interface.

threadSafe - - a flag indicating if the cach store should be synchronized to allow correct operation under multi-threaded access. If true, the cache store is synchronized. If false the cache store is unsynchronized and the cache is not thread safe.

resolution - - the resolution in seconds of the cache timer. A cache does not query the system time on every get() invocation. Rather the cache updates its notion of the current time every 'resolution' seconds.

Method Detail

create

public void create()

Initializes the cache for use. Prior to this the cache has no store.

Specified by:

create in interface CachePolicy

start

public void start()

Schedules this with the class resolutionTimer Timer object for execution every resolution seconds.

Specified by:

start in interface CachePolicy

stop

public void stop()

Stop cancels the resolution timer and flush()es the cache.

Specified by:

stop in interface CachePolicy

destroy

public void destroy()

Clears the cache of all entries.

Specified by:

destroy in interface CachePolicy

get

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

Get the cache value for key if it has not expired. If the TimedEntry is expired its destroy method is called and then removed from the cache.

Specified by:

get in interface CachePolicy

Parameters:

key - the key paired with the object

Returns:

the TimedEntry value or the original value if it was not an instance of TimedEntry if key is in the cache, null otherwise.

See Also:

CachePolicy.peek(java.lang.Object)

peek

public java.lang.Object peek(java.lang.Object key)

Get the cache value for key. This method does not check to see if the entry has expired.

Specified by:

peek in interface CachePolicy

Parameters:

key - the key paired with the object

Returns:

the TimedEntry value or the original value if it was not an instancee of TimedEntry if key is in the cache, null otherwise.

See Also:

CachePolicy.get(java.lang.Object)

insert

public void insert(java.lang.Object key,
                   java.lang.Object value)

Insert a value into the cache. In order to have the cache entry reshresh itself value would have to implement TimedEntry and implement the required refresh() method logic.

Specified by:

insert in interface CachePolicy

Parameters:

key - - the key for the cache entry

value - - Either an instance of TimedEntry that will be inserted without change, or an abitrary value that will be wrapped in a non-refreshing TimedEntry.

See Also:

CachePolicy.remove(java.lang.Object)

remove

public void remove(java.lang.Object key)

Remove the entry associated with key and call destroy on the entry if found.

Specified by:

remove in interface CachePolicy

Parameters:

key - the key paired with the object

See Also:

CachePolicy.insert(java.lang.Object, java.lang.Object)

flush

public void flush()

Remove all entries from the cache.

Specified by:

flush in interface CachePolicy

size

public int size()

Specified by:

size in interface CachePolicy

Returns:

the size of the cache

getValidKeys

public java.util.List getValidKeys()

Get the list of keys for entries that are not expired.

Returns:

A List of the keys corresponding to valid entries

getDefaultLifetime

public int getDefaultLifetime()

Get the default lifetime of cache entries.

Returns:

default lifetime in seconds of cache entries.

setDefaultLifetime

public void setDefaultLifetime(int defaultLifetime)

Set the default lifetime of cache entries for new values added to the cache.

Parameters:

defaultLifetime - - lifetime in seconds of cache values that do not implement TimedEntry.

getResolution

public int getResolution()

Get the frequency of the current time snapshot.

Returns:

the current timer resolution in seconds.

setResolution

public void setResolution(int resolution)

Set the cache timer resolution

Parameters:

resolution - - the resolution in seconds of the cache timer. A cache does not query the system time on every get() invocation. Rather the cache updates its notion of the current time every 'resolution' seconds.

run

public void run()

The TimerTask run method. It updates the cache time to the current system time.

Specified by:

run in interface java.lang.Runnable

Specified by:

run in class java.util.TimerTask

currentTimeMillis

public long currentTimeMillis()

Get the cache time.

Returns:

the cache time last obtained from System.currentTimeMillis()

peekEntry

public TimedCachePolicy.TimedEntry peekEntry(java.lang.Object key)

Get the raw TimedEntry for key without performing any expiration check.

Parameters:

key -

Returns:

the TimedEntry value associated with key if one exists, null otherwise.