TimedCachePolicy (JBoss/Common API) - JBoss 3.2.7 common API Documentation 英文版文档

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org.jboss.util
Class TimedCachePolicy

java.lang.Object
  java.util.TimerTask
      org.jboss.util.TimedCachePolicy

All Implemented Interfaces:: CachePolicy, Runnable

public class TimedCachePolicy
extends 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: 1.3.2.2 $
Author:: Scott Stark.

Nested Class Summary

static interface TimedCachePolicy.TimedEntry
          The interface that cache entries support.

Field Summary

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

protected Map entryMap
          The map of cached TimedEntry objects.

protected long now
          The caches notion of the current time

protected int resolution
          The resolution in seconds of the cach current time

protected static Timer resolutionTimer


protected boolean threadSafe
          A flag indicating if entryMap should be synchronized

Constructor Summary

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

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.

Object get(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.

List getValidKeys()
          Get the list of keys for entries that are not expired.

void insert(Object key, Object value)
          Insert a value into the cache.

Object peek(Object key)
          Get the cache value for key.

TimedCachePolicy.TimedEntry peekEntry(Object key)
          Get the raw TimedEntry for key without performing any expiration check.

void remove(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()
          Get the size of the cache.

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

resolutionTimer

protected static Timer resolutionTimer

entryMap

protected 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

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.

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 Object get(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 Object peek(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(Object key,
                   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(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()

Description copied from interface: CachePolicy

Get the size of the cache.

Specified by:: size in interface CachePolicy

getValidKeys

public 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 Runnable

currentTimeMillis

public long currentTimeMillis()

Get the cache time.

Returns:: the cache time last obtained from System.currentTimeMillis()

peekEntry

public TimedCachePolicy.TimedEntry peekEntry(Object key)

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

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

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Nested Class Summary
`static interface`	`TimedCachePolicy.TimedEntry` The interface that cache entries support.

Field Summary
`protected int`	`defaultLifetime` The lifetime in seconds to use for objects inserted that do not implement the TimedEntry interface.
`protected Map`	`entryMap` The map of cached TimedEntry objects.
`protected long`	`now` The caches notion of the current time
`protected int`	`resolution` The resolution in seconds of the cach current time
`protected static Timer`	`resolutionTimer`
`protected boolean`	`threadSafe` A flag indicating if entryMap should be synchronized

Constructor Summary
`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
`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.
`Object`	`get(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.
`List`	`getValidKeys()` Get the list of keys for entries that are not expired.
`void`	`insert(Object key, Object value)` Insert a value into the cache.
`Object`	`peek(Object key)` Get the cache value for key.
`TimedCachePolicy.TimedEntry`	`peekEntry(Object key)` Get the raw TimedEntry for key without performing any expiration check.
`void`	`remove(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()` Get the size of the cache.
`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.

TimedCachePolicy (JBoss/Common API) - JBoss 3.2.7 common API Documentation 英文版文档

org.jboss.util Class TimedCachePolicy

resolutionTimer

entryMap

defaultLifetime

threadSafe

now

resolution

TimedCachePolicy

TimedCachePolicy

TimedCachePolicy

create

start

stop

destroy

get

peek

insert

remove

flush

size

getValidKeys

getDefaultLifetime

setDefaultLifetime

getResolution

setResolution

run

currentTimeMillis

peekEntry

org.jboss.util
Class TimedCachePolicy