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This library contains class that are used across all Cake projects
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/*
* Copyright 2008 Kasper Nielsen.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://cake.codehaus.org/LICENSE
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package org.codehaus.cake.cache;
import java.io.Serializable;
import java.util.AbstractMap;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import org.codehaus.cake.attribute.AttributeMap;
import org.codehaus.cake.attribute.Attributes;
import org.codehaus.cake.attribute.DoubleAttribute;
import org.codehaus.cake.attribute.LongAttribute;
import org.codehaus.cake.attribute.common.TimeInstanceAttribute;
import org.codehaus.cake.internal.util.CollectionUtils;
/**
* Various Factory and utility methods.
*
* @author Kasper Nielsen
* @version $Id: CacheServices.java 469 2007-11-17 14:32:25Z kasper $
*/
public final class Caches {
/**
* The empty cache (immutable). This cache is serializable.
*
* @see #emptyCache()
*/
static final Cache EMPTY_CACHE = new EmptyCache();
// /CLOVER:OFF
/** Cannot instantiate. */
private Caches() {}
// /CLOVER:ON
/**
* Returns a Runnable that when executed will call the clear method on the specified cache.
*
* The following example shows how this can be used to clear the cache every hour.
*
*
* Cache c = somecache;
* ScheduledExecutorService ses = c.with().executors().getScheduledExecutorService();
* ses.scheduleAtFixedRate(Caches.clearAsRunnable(c), 0, 60 * 60, TimeUnit.SECONDS);
*
*
*
* @param cache
* the cache on which to call evict
* @return a runnable where invocation of the run method will clear the specified cache
* @throws NullPointerException
* if the specified cache is null.
*/
public static Runnable clearAsRunnable(Cache cache) {
return new ClearRunnable(cache);
}
/**
* Returns the empty cache (immutable). This cache is serializable.
*
* This example illustrates the type-safe way to obtain an empty cache:
*
*
* Cache<Integer, String> c = Caches.emptyCache();
*
*
* Implementation note: Implementations of this method need not create a separate Cache object for each
* call. Using this method is likely to have comparable cost to using the like-named field. (Unlike this method, the
* field does not provide type safety.)
*
* @see #EMPTY_CACHE
*/
@SuppressWarnings("unchecked")
public static Cache emptyCache() {
return EMPTY_CACHE;
}
/**
* A runnable used for calling clear on a cache.
*/
static class ClearRunnable implements Runnable {
/** The cache to call clear on. */
private final Cache cache;
/**
* Creates a new ClearRunnable.
*
* @param cache
* the cache to call clear on
*/
ClearRunnable(Cache cache) {
if (cache == null) {
throw new NullPointerException("cache is null");
}
this.cache = cache;
}
/** {@inheritDoc} */
public void run() {
cache.clear();
}
}
static final class CostAttribute extends DoubleAttribute {
/** serialVersionUID. */
private static final long serialVersionUID = -2353351535602223603L;
/** Creates a new CostAttribute. */
CostAttribute() {
super("Cost", 1.0);
}
/** @return Preserves singleton property */
private Object readResolve() {
return CacheEntry.COST;
}
}
/**
* The empty cache.
*/
static class EmptyCache extends AbstractMap implements Cache, Serializable {
/** serialVersionUID. */
private static final long serialVersionUID = -5245003832315997155L;
/** {@inheritDoc} */
public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
return false;
}
/** {@inheritDoc} */
@SuppressWarnings("unchecked")
@Override
public Set> entrySet() {
return Collections.EMPTY_MAP.entrySet();
}
/** {@inheritDoc} */
public Map getAll(Collection keys) {
CollectionUtils.checkCollectionForNulls(keys);
Map result = new HashMap(keys.size());
for (K key : keys) {
result.put(key, null);
}
return result;
}
/** {@inheritDoc} */
public Set> serviceKeySet() {
return Collections.EMPTY_SET;
}
/** {@inheritDoc} */
public CacheEntry getEntry(K key) {
return null;
}
/** {@inheritDoc} */
public String getName() {
return "emptymap";
}
/** {@inheritDoc} */
public T getService(Class serviceType) {
return getService(serviceType, Attributes.EMPTY_ATTRIBUTE_MAP);
}
/** {@inheritDoc} */
public T getService(Class serviceType, AttributeMap attributes) {
if (serviceType == null) {
throw new NullPointerException("serviceType is null");
} else if (attributes == null) {
throw new NullPointerException("attributes is null");
}
throw new UnsupportedOperationException("Unknown service " + serviceType);
}
/** {@inheritDoc} */
public boolean hasService(Class serviceType) {
return false;
}
/** {@inheritDoc} */
public boolean isShutdown() {
return false;
}
/** {@inheritDoc} */
public boolean isStarted() {
return false;
}
/** {@inheritDoc} */
public boolean isTerminated() {
return false;
}
/** {@inheritDoc} */
public V peek(K key) {
return null;
}
/** {@inheritDoc} */
public CacheEntry peekEntry(K key) {
return null;
}
/** {@inheritDoc} */
public V putIfAbsent(K key, V value) {
throw new UnsupportedOperationException();
}
/** @return Preserves singleton property */
private Object readResolve() {
return EMPTY_CACHE;
}
/** {@inheritDoc} */
public boolean remove(Object key, Object value) {
return false;
}
/** {@inheritDoc} */
public void removeAll(Collection keys) {}
/** {@inheritDoc} */
public V replace(K key, V value) {
throw new UnsupportedOperationException();// ??
}
/** {@inheritDoc} */
public boolean replace(K key, V oldValue, V newValue) {
return false;
}
/** {@inheritDoc} */
public void shutdown() {}
/** {@inheritDoc} */
public void shutdownNow() {}
/** {@inheritDoc} */
public CacheServices with() {
return new CacheServices(this);
}
}
/**
* The Hits attribute indicates the number of hits for a cache element. The mapped value must be of a
* type long between 0 and {@link Long#MAX_VALUE}.
*/
static final class HitsAttribute extends LongAttribute {
/** serialVersionUID. */
private static final long serialVersionUID = -2353351535602223603L;
/** Creates a new SizeAttribute. */
HitsAttribute() {
super("Hits");
}
/** {@inheritDoc} */
@Override
public boolean isValid(long hits) {
return hits >= 0;
}
/** @return Preserves singleton property */
private Object readResolve() {
return CacheEntry.HITS;
}
}
static final class SizeAttribute extends LongAttribute {
/** serialVersionUID. */
private static final long serialVersionUID = -2353351535602223603L;
/** Creates a new SizeAttribute. */
SizeAttribute() {
super("Size", 1);
}
/** {@inheritDoc} */
@Override
public void checkValid(long value) {
if (value < 0) {
throw new IllegalArgumentException("invalid size (size = " + value + ")");
}
}
/** {@inheritDoc} */
@Override
public boolean isValid(long value) {
return value >= 0;
}
/** @return Preserves singleton property */
private Object readResolve() {
return CacheEntry.SIZE;
}
}
static final class TimeAccessedAttribute extends TimeInstanceAttribute {
/** serialVersionUID. */
private static final long serialVersionUID = -2353351535602223603L;
/** Creates a new DateCreatedAttribute. */
TimeAccessedAttribute() {
super("AccessTime");
}
/** @return Preserves singleton property */
private Object readResolve() {
return CacheEntry.TIME_ACCESSED;
}
}
static final class TimeCreatedAttribute extends TimeInstanceAttribute {
/** serialVersionUID. */
private static final long serialVersionUID = -2353351535602223603L;
/** Creates a new DateCreatedAttribute. */
TimeCreatedAttribute() {
super("CreationTime");
}
/** @return Preserves singleton property */
private Object readResolve() {
return CacheEntry.TIME_CREATED;
}
}
static final class TimeModificedAttribute extends TimeInstanceAttribute {
/** serialVersionUID. */
private static final long serialVersionUID = -2353351535602223603L;
/** Creates a new DateCreatedAttribute. */
TimeModificedAttribute() {
super("ModificationTime");
}
/** @return Preserves singleton property */
private Object readResolve() {
return CacheEntry.TIME_MODIFIED;
}
}
/**
* This key can be used to indicate how long time an object should live. The time-to-live value should be a long
* between 1 and {@link Long#MAX_VALUE} measured in nanoseconds. Use {@link java.util.concurrent.TimeUnit} to
* convert between different time units.
*
*/
// static final class TimeToLiveAttribute extends DurationAttribute {
//
// /** serialVersionUID. */
// private static final long serialVersionUID = -2353351535602223603L;
//
// /** The singleton instance of this attribute. */
// public static final TimeToLiveAttribute TIME_TO_LIVE = new TimeToLiveAttribute();
//
// /** Creates a new TimeToLiveAttribute. */
// TimeToLiveAttribute() {
// super("TimeToLive");
// }
//
// /** @return Preserves singleton property */
// private Object readResolve() {
// return TIME_TO_LIVE;
// }
// }
/**
* The Version attribute indicates the number of hits for a cache element. The mapped value must be of a
* type long between 0 and {@link Long#MAX_VALUE}.
*/
static final class VersionAttribute extends LongAttribute {
/** serialVersionUID. */
private static final long serialVersionUID = -235335135602223603L;
/** Creates a new SizeAttribute. */
VersionAttribute() {
super("Version", 1);
}
/** {@inheritDoc} */
@Override
public boolean isValid(long hits) {
return hits > 0;
}
/** @return Preserves singleton property */
private Object readResolve() {
return CacheEntry.VERSION;
}
}
}
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