software.amazon.jdbc.util.storage

Class ExpirationCache<K,V>

java.lang.Object

software.amazon.jdbc.util.storage.ExpirationCache<K,V>

Type Parameters:

K - the type of the keys in the cache.

V - the type of the values in the cache.

public class ExpirationCache<K,V>
extends java.lang.Object

A cache that can be used to store values that expire after a configured period of time. Entries are disposed when removed from the cache if an ItemDisposalFunc is defined.

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Map<K,CacheItem<V>>	cache
protected static long	DEFAULT_TIME_TO_LIVE_NANOS
protected boolean	isRenewableExpiration
protected ItemDisposalFunc<V>	itemDisposalFunc
protected ShouldDisposeFunc<V>	shouldDisposeFunc
protected long	timeToLiveNanos

Constructor Summary

Constructors

Constructor and Description
ExpirationCache()
ExpirationCache(boolean isRenewableExpiration, long timeToLiveNanos, @Nullable ShouldDisposeFunc<V> shouldDisposeFunc, @Nullable ItemDisposalFunc<V> itemDisposalFunc) Constructs an ExpirationCache instance.

Method Summary

Modifier and Type	Method and Description
void	clear() Removes and disposes of all entries in the cache.
V	computeIfAbsent(K key, java.util.function.Function<? super K,? extends V> mappingFunction) If a value does not exist for the given key or the existing value is expired and non-renewable, stores the value returned by the given mapping function, unless the function returns null, in which case the key will be removed.
boolean	exists(K key) Indicates whether a non-expired value is stored at the given key.
V	get(K key) Retrieves the value stored at the given key.
java.util.Map<K,V>	getEntries() Gets a map copy of all entries in the cache, including expired entries.
V	put(K key, V value) Stores the given value at the given key.
V	remove(K key) Removes and disposes of the value stored at the given key.
protected V	removeAndDispose(K key)
void	removeExpiredEntries() Removes and disposes of all expired entries in the cache.
void	removeIfExpired(K key) Removes and disposes of the item stored at the given key if it is expired and the ShouldDisposeFunc (if defined) returns true for the item.
int	size() Gets the current size of the cache, including expired entries.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_TIME_TO_LIVE_NANOS

protected static final long DEFAULT_TIME_TO_LIVE_NANOS

cache

protected final java.util.Map<K,CacheItem<V>> cache

isRenewableExpiration

protected final boolean isRenewableExpiration

timeToLiveNanos

protected final long timeToLiveNanos

shouldDisposeFunc

protected final ShouldDisposeFunc<V> shouldDisposeFunc

itemDisposalFunc

protected final ItemDisposalFunc<V> itemDisposalFunc

Constructor Detail

ExpirationCache

public ExpirationCache()

ExpirationCache

public ExpirationCache(boolean isRenewableExpiration,
                       long timeToLiveNanos,
                       @Nullable ShouldDisposeFunc<V> shouldDisposeFunc,
                       @Nullable ItemDisposalFunc<V> itemDisposalFunc)

Constructs an ExpirationCache instance.

Parameters:

isRenewableExpiration - controls whether an item's expiration should be renewed when retrieved. If the item is expired when it is retrieved and isRenewableExpiration is true, the item's expiration will be renewed and the item will be returned.

timeToLiveNanos - the duration that the item should sit in the cache before being considered expired, in nanoseconds.

shouldDisposeFunc - a function defining the conditions under which an expired entry should be cleaned up. If null is passed, the entry will always be cleaned up if it is expired.

itemDisposalFunc - a function defining how to dispose of an item when it is removed. If null is passed, the item will be removed without performing any additional operations.

Method Detail

put

public V put(K key,
             V value)

Stores the given value at the given key.

Parameters:

key - the key at which the value should be stored.

value - the value to store.

Returns:

the previous value stored at the given key, or null if there was no previous value. If there was a previous value it will also be disposed.

computeIfAbsent

public V computeIfAbsent(K key,
                         java.util.function.Function<? super K,? extends V> mappingFunction)

If a value does not exist for the given key or the existing value is expired and non-renewable, stores the value returned by the given mapping function, unless the function returns null, in which case the key will be removed.

Parameters:

key - the key for the new or existing value.

mappingFunction - the function to call to compute a new value.

Returns:

the current (existing or computed) value associated with the specified key, or null if the computed value is null.

get

public V get(K key)

Retrieves the value stored at the given key.

Parameters:

key - the key for the value.

Returns:

the value stored at the given key, or null if there is no existing value or the existing value is expired.

exists

public boolean exists(K key)

Indicates whether a non-expired value is stored at the given key.

Parameters:

key - the key for the value.

Returns:

true if there is a non-expired value stored at the given key, otherwise returns false.

remove

public V remove(K key)

Removes and disposes of the value stored at the given key.

Parameters:

key - the key associated with the value to be removed and disposed.

Returns:

the value removed from the cache, or null if the key does not exist in the cache. If the value was expired, it will still be returned.

removeAndDispose

protected V removeAndDispose(K key)

removeExpiredEntries

public void removeExpiredEntries()

Removes and disposes of all expired entries in the cache.

removeIfExpired

public void removeIfExpired(K key)

Removes and disposes of the item stored at the given key if it is expired and the ShouldDisposeFunc (if defined) returns true for the item. Otherwise, does nothing.

Parameters:

key - the key for the value to check for removal.

clear

public void clear()

Removes and disposes of all entries in the cache.

getEntries

public java.util.Map<K,V> getEntries()

Gets a map copy of all entries in the cache, including expired entries.

Returns:

a map copy of all entries in the cache, including expired entries.

size

public int size()

Gets the current size of the cache, including expired entries.

Returns:

the current size of the cache, including expired entries.