javax.cache.ExpiryPolicy Maven / Gradle / Ivy
/**
* Copyright (c) 2011 Terracotta, Inc.
* Copyright (c) 2011 Oracle and/or its affiliates.
*
* All rights reserved. Use is subject to license terms.
*/
package javax.cache;
import javax.cache.Cache.Entry;
import javax.cache.Configuration.Duration;
/**
* Defines functions to determine when cache entries will expire based on
* creation, access and modification operations.
*
* Each of the functions return a {@link Duration} that of which specifies the
* amount of time that must pass before a cache entry is considered expired.
* This {@link Duration} is often called a "time-to-live", commonly abbreviated
* to simply "TTL".
*
* @param the type of keys
* @param the type of values
*
* @author Brian Oliver
*/
public interface ExpiryPolicy {
/**
* Gets the time-to-live before the newly Cache.Entry is considered expired.
*
* This method is called after a Cache.Entry is created, but before the said
* entry is added to a cache, to determine the {@link Duration} before the
* said entry expires. If a {@link Duration#ZERO} is returned the Cache.Entry is
* considered to be already expired and will not be added to the Cache.
*
* @param entry the cache entry that was created
* @return the duration until the entry expires
*/
Duration getTTLForCreatedEntry(Entry entry);
/**
* Gets the time-to-live before the accessed Cache.Entry is considered expired.
*
* This method is called after a Cache.Entry is accessed to determine the
* {@link Duration} before the said entry expires in the future. If a
* {@link Duration#ZERO} is returned the Cache.Entry will be considered
* expired for future access.
*
* @param entry the cache entry that was accessed
* @param duration the current {@link Duration} before the entry expires
* @return the duration until the entry expires
*/
Duration getTTLForAccessedEntry(Entry entry, Duration duration);
/**
* Gets the time-to-live before the modified Cache.Entry is considered expired.
*
* This method is called after a Cache.Entry is modified to determine the
* {@link Duration} before the updated entry expires. If a
* {@link Duration#ZERO} is returned the Cache.Entry is considered already
* expired.
*
* @param entry the cache entry that was modified
* @param duration the current {@link Duration} before the updated entry expires
* @return the duration until the entry expires
*/
Duration getTTLForModifiedEntry(Entry entry, Duration duration);
/**
* A {@link ExpiryPolicy} that defines the expiry {@link Duration}
* of a Cache Entry based on the last time it was accessed.
*
* @param the type of cache keys
* @param the type of cache values
*/
public static final class Accessed implements ExpiryPolicy {
/**
* The {@link Duration} a Cache Entry should be available before it expires.
*/
private Duration expiryDuration;
/**
* Constructs an {@link Accessed} {@link ExpiryPolicy}.
*
* @param expiryDuration the {@link Duration} a Cache Entry should exist be
* before it expires after being accessed
*/
public Accessed(Duration expiryDuration) {
this.expiryDuration = expiryDuration;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForCreatedEntry(Entry entry) {
//for newly created entries we use the specified expiry duration
return expiryDuration;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForAccessedEntry(Entry entry, Duration duration) {
//when a cache entry is accessed, we return the specified expiry duration,
//ignoring the current expiry duration
return expiryDuration;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForModifiedEntry(Entry entry, Duration duration) {
//modifying a cache entry has no affect on the current expiry duration
return duration;
}
/**
* {@inheritDoc}
*/
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((expiryDuration == null) ? 0 : expiryDuration.hashCode());
return result;
}
/**
* {@inheritDoc}
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (!(obj instanceof Accessed)) {
return false;
}
Accessed other = (Accessed) obj;
if (expiryDuration == null) {
if (other.expiryDuration != null) {
return false;
}
} else if (!expiryDuration.equals(other.expiryDuration)) {
return false;
}
return true;
}
}
/**
* A {@link ExpiryPolicy} that defines the expiry {@link Duration}
* of a Cache Entry based on the last time it was modified.
*
* @param the type of cache keys
* @param the type of cache values
*/
public static final class Modified implements ExpiryPolicy {
/**
* The {@link Duration} a Cache Entry should be available before it expires.
*/
private Duration expiryDuration;
/**
* Constructs an {@link Modified} {@link ExpiryPolicy}.
*
* @param expiryDuration the {@link Duration} a Cache Entry should exist be
* before it expires after being modified
*/
public Modified(Duration expiryDuration) {
this.expiryDuration = expiryDuration;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForCreatedEntry(Entry entry) {
//for newly created entries we use the specified expiry duration
return expiryDuration;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForAccessedEntry(Entry entry, Duration duration) {
//accessing a cache entry has no affect on the current expiry duration
return duration;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForModifiedEntry(Entry entry, Duration duration) {
//when a cache entry is modified, we return the specified expiry duration,
//ignoring the current expiry duration
return expiryDuration;
}
/**
* {@inheritDoc}
*/
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((expiryDuration == null) ? 0 : expiryDuration.hashCode());
return result;
}
/**
* {@inheritDoc}
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (!(obj instanceof Modified)) {
return false;
}
Modified other = (Modified) obj;
if (expiryDuration == null) {
if (other.expiryDuration != null) {
return false;
}
} else if (!expiryDuration.equals(other.expiryDuration)) {
return false;
}
return true;
}
}
/**
* The default {@link ExpiryPolicy} specifies that Cache Entries
* won't expire. This however doesn't mean they won't be expired if an
* underlying implementation needs to free-up resources where by it may
* choose to expire entries that are not due to expire.
*/
public static final class Default implements ExpiryPolicy {
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForCreatedEntry(Entry entry) {
return Duration.ETERNAL;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForAccessedEntry(Entry entry, Duration duration) {
return duration;
}
/**
* {@inheritDoc}
*/
@Override
public Duration getTTLForModifiedEntry(Entry entry, Duration duration) {
return duration;
}
/**
* {@inheritDoc}
*/
@Override
public int hashCode() {
return Default.class.hashCode();
}
/**
* {@inheritDoc}
*/
@Override
public boolean equals(Object other) {
return other instanceof Default;
}
}
}
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