com.aoindustries.cache

Class BackgroundCache<K,V,E extends Exception>

java.lang.Object

com.aoindustries.cache.BackgroundCache<K,V,E>

public class BackgroundCache<K,V,E extends Exception>
extends Object

A cache that is refreshed in the background, implementing only get, put, and size. There is no remove; background cleaning is performed on the underlying map.

When the system is sitting idle, all cache entries are expired and there is zero overhead. Background refreshes only happen on recently used keys.

Author:

AO Industries, Inc.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	BackgroundCache.Refresher<K,V,E extends Exception> A callable used to refresh the cache.
static class	BackgroundCache.Result<V,E extends Exception> The result of a refresh.

Constructor Summary

Constructors

Constructor and Description
BackgroundCache(String name, Class<E> exceptionClass, long refreshInterval, long expirationAge) Uses the default logger.
BackgroundCache(String name, Class<E> exceptionClass, long refreshInterval, long expirationAge, Logger logger)

Method Summary

Modifier and Type	Method and Description
BackgroundCache.Result<V,E>	get(K key) Gets a cached result for the given key, null if not cached.
BackgroundCache.Result<V,E>	get(K key, BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher) Gets the value if currently in the cache.
BackgroundCache.Result<V,E>	put(K key, BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher) Runs the refresher immediately to obtain the result, then places an entry into the cache, replacing any existing entry under this key.
void	put(K key, BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher, E exception) Places a result into the cache, replacing any existing entry under this key.
void	put(K key, BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher, V value) Places a result into the cache, replacing any existing entry under this key.
int	size() Gets the current size of the cache.
void	stop() Stops this cache.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

BackgroundCache

public BackgroundCache(String name,
                       Class<E> exceptionClass,
                       long refreshInterval,
                       long expirationAge,
                       Logger logger)

Parameters:

name - The name resources are based on, such as background thread names.

exceptionClass - The class object used to verify exception types are runtime

refreshInterval - The time between cache entry refreshes

expirationAge - The time the a cache entry will expire if it has not been accessed, the actual expiration may happen after this time as it is only checked during refreshes.

BackgroundCache

public BackgroundCache(String name,
                       Class<E> exceptionClass,
                       long refreshInterval,
                       long expirationAge)

Uses the default logger.

See Also:

BackgroundCache(java.lang.String, java.lang.Class, long, long, java.util.logging.Logger)

Method Detail

toString

public String toString()

Overrides:

toString in class Object

stop

public void stop()

Stops this cache. This cache should not be used after this is called. Repeated calls to stop are allowed.

get

public BackgroundCache.Result<V,E> get(K key,
                                       BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher)

Gets the value if currently in the cache. If not, Runs the refresher immediately to obtain the result, then places an entry into the cache.

Returns:

The result obtained from either the cache or this refresher

See Also:

get(java.lang.Object), put(java.lang.Object, com.aoindustries.cache.BackgroundCache.Refresher)

get

public BackgroundCache.Result<V,E> get(K key)

Gets a cached result for the given key, null if not cached. Extends the expiration of the cache entry.

put

public BackgroundCache.Result<V,E> put(K key,
                                       BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher)

Runs the refresher immediately to obtain the result, then places an entry into the cache, replacing any existing entry under this key.

Returns:

The result obtained from this refresher

put

public void put(K key,
                BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher,
                V value)

Places a result into the cache, replacing any existing entry under this key.

put

public void put(K key,
                BackgroundCache.Refresher<? super K,? extends V,? extends E> refresher,
                E exception)

Places a result into the cache, replacing any existing entry under this key.

size

public int size()

Gets the current size of the cache.