software.amazon.jdbc.util.storage

Class ExternallyManagedCache<K,V>

java.lang.Object

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

Type Parameters:

K - the type of the keys in the cache.

V - the type of the values in the cache.

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

A cache with expiration functionality that does not automatically remove expired entries. The removal of expired entries is instead handled by an external class. This class is similar to ExpirationCache, but allows users to manually renew item expiration and provides more control over the conditions in which items are removed. Disposal of removed items should be handled outside of this class.

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Map<K,CacheItem<V>>	cache
protected long	timeToLiveNanos

Constructor Summary

Constructors

Constructor and Description
ExternallyManagedCache(long timeToLiveNanos) Constructs an externally managed cache.

Method Summary

Modifier and Type	Method and Description
V	computeIfAbsent(K key, java.util.function.Function<? super K,? extends V> mappingFunction) If a value does not exist for the given key, stores the value returned by the given mapping function, unless the function returns null, in which case the key will be removed.
void	extendExpiration(K key) Extends the expiration of the item stored at the given key, if it exists.
V	get(K key) Get 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 in the cache at the given key.
V	remove(K key) Removes the value stored at the given key from the cache.
V	removeExpiredIf(K key, java.util.function.Predicate<V> predicate) Removes the value stored at the given key if it is expired and the given predicate returns true for the value.
V	removeIf(K key, java.util.function.Predicate<V> predicate) Removes the value stored at the given key if the given predicate returns true for the value.

Methods inherited from class java.lang.Object

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

Field Detail

cache

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

timeToLiveNanos

protected final long timeToLiveNanos

Constructor Detail

ExternallyManagedCache

public ExternallyManagedCache(long timeToLiveNanos)

Constructs an externally managed cache.

Parameters:

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

Method Detail

put

public V put(K key,
             V value)

Stores the given value in the cache at the given key.

Parameters:

key - the key for the value.

value - the value to store.

Returns:

the previous value stored at the key, or null if there was no value stored at the key.

get

public V get(K key)

Get the value stored at the given key. If the value is expired, null will be returned.

Parameters:

key - the key for the value.

Returns:

the value stored at the given key, or null if the key does not exist or the value is expired.

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, 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.

extendExpiration

public void extendExpiration(K key)

Extends the expiration of the item stored at the given key, if it exists.

Parameters:

key - the key for the value whose expiration should be extended.

remove

public V remove(K key)

Removes the value stored at the given key from the cache.

Parameters:

key - the key for the value to be removed.

Returns:

the value that was removed, or null if the key did not exist.

removeIf

public V removeIf(K key,
                  java.util.function.Predicate<V> predicate)

Removes the value stored at the given key if the given predicate returns true for the value. Otherwise, does nothing.

Parameters:

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

predicate - a predicate lambda that defines the condition under which the value should be removed.

Returns:

the removed value, or null if no value was removed.

removeExpiredIf

public V removeExpiredIf(K key,
                         java.util.function.Predicate<V> predicate)

Removes the value stored at the given key if it is expired and the given predicate returns true for the value. Otherwise, does nothing.

Parameters:

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

predicate - a predicate lambda that defines the condition under which the value should be removed if it is also expired.

Returns:

the removed value, or null if no value was removed.

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.