/*
* Copyright (C) 2009 The Guava Authors
*
* 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://www.apache.org/licenses/LICENSE-2.0
*
* 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 com.google.common.cache;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Ascii;
import com.google.common.base.Equivalence;
import com.google.common.base.MoreObjects;
import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import com.google.common.base.Ticker;
import com.google.common.cache.AbstractCache.SimpleStatsCounter;
import com.google.common.cache.AbstractCache.StatsCounter;
import com.google.common.cache.LocalCache.Strength;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.ConcurrentModificationException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.CheckReturnValue;
/**
* <p>A builder of {@link LoadingCache} and {@link Cache} instances having any combination of the
* following features:
*
* <ul>
* <li>automatic loading of entries into the cache
* <li>least-recently-used eviction when a maximum size is exceeded
* <li>time-based expiration of entries, measured since last access or last write
* <li>keys automatically wrapped in {@linkplain WeakReference weak} references
* <li>values automatically wrapped in {@linkplain WeakReference weak} or
* {@linkplain SoftReference soft} references
* <li>notification of evicted (or otherwise removed) entries
* <li>accumulation of cache access statistics
* </ul>
*
* <p>These features are all optional; caches can be created using all or none of them. By default
* cache instances created by {@code CacheBuilder} will not perform any type of eviction.
*
* <p>Usage example: <pre> {@code
*
* LoadingCache<Key, Graph> graphs = CacheBuilder.newBuilder()
* .maximumSize(10000)
* .expireAfterWrite(10, TimeUnit.MINUTES)
* .removalListener(MY_LISTENER)
* .build(
* new CacheLoader<Key, Graph>() {
* public Graph load(Key key) throws AnyException {
* return createExpensiveGraph(key);
* }
* });}</pre>
*
* <p>Or equivalently, <pre> {@code
*
* // In real life this would come from a command-line flag or config file
* String spec = "maximumSize=10000,expireAfterWrite=10m";
*
* LoadingCache<Key, Graph> graphs = CacheBuilder.from(spec)
* .removalListener(MY_LISTENER)
* .build(
* new CacheLoader<Key, Graph>() {
* public Graph load(Key key) throws AnyException {
* return createExpensiveGraph(key);
* }
* });}</pre>
*
* <p>The returned cache is implemented as a hash table with similar performance characteristics to
* {@link ConcurrentHashMap}. It implements all optional operations of the {@link LoadingCache} and
* {@link Cache} interfaces. The {@code asMap} view (and its collection views) have <i>weakly
* consistent iterators</i>. This means that they are safe for concurrent use, but if other threads
* modify the cache after the iterator is created, it is undefined which of these changes, if any,
* are reflected in that iterator. These iterators never throw {@link
* ConcurrentModificationException}.
*
* <p><b>Note:</b> by default, the returned cache uses equality comparisons (the
* {@link Object#equals equals} method) to determine equality for keys or values. However, if
* {@link #weakKeys} was specified, the cache uses identity ({@code ==})
* comparisons instead for keys. Likewise, if {@link #weakValues} or {@link #softValues} was
* specified, the cache uses identity comparisons for values.
*
* <p>Entries are automatically evicted from the cache when any of
* {@linkplain #maximumSize(long) maximumSize}, {@linkplain #maximumWeight(long) maximumWeight},
* {@linkplain #expireAfterWrite expireAfterWrite},
* {@linkplain #expireAfterAccess expireAfterAccess}, {@linkplain #weakKeys weakKeys},
* {@linkplain #weakValues weakValues}, or {@linkplain #softValues softValues} are requested.
*
* <p>If {@linkplain #maximumSize(long) maximumSize} or
* {@linkplain #maximumWeight(long) maximumWeight} is requested entries may be evicted on each cache
* modification.
*
* <p>If {@linkplain #expireAfterWrite expireAfterWrite} or
* {@linkplain #expireAfterAccess expireAfterAccess} is requested entries may be evicted on each
* cache modification, on occasional cache accesses, or on calls to {@link Cache#cleanUp}. Expired
* entries may be counted by {@link Cache#size}, but will never be visible to read or write
* operations.
*
* <p>If {@linkplain #weakKeys weakKeys}, {@linkplain #weakValues weakValues}, or
* {@linkplain #softValues softValues} are requested, it is possible for a key or value present in
* the cache to be reclaimed by the garbage collector. Entries with reclaimed keys or values may be
* removed from the cache on each cache modification, on occasional cache accesses, or on calls to
* {@link Cache#cleanUp}; such entries may be counted in {@link Cache#size}, but will never be
* visible to read or write operations.
*
* <p>Certain cache configurations will result in the accrual of periodic maintenance tasks which
* will be performed during write operations, or during occasional read operations in the absence of
* writes. The {@link Cache#cleanUp} method of the returned cache will also perform maintenance, but
* calling it should not be necessary with a high throughput cache. Only caches built with
* {@linkplain #removalListener removalListener}, {@linkplain #expireAfterWrite expireAfterWrite},
* {@linkplain #expireAfterAccess expireAfterAccess}, {@linkplain #weakKeys weakKeys},
* {@linkplain #weakValues weakValues}, or {@linkplain #softValues softValues} perform periodic
* maintenance.
*
* <p>The caches produced by {@code CacheBuilder} are serializable, and the deserialized caches
* retain all the configuration properties of the original cache. Note that the serialized form does
* <i>not</i> include cache contents, but only configuration.
*
* <p>See the Guava User Guide article on <a href=
* "http://code.google.com/p/guava-libraries/wiki/CachesExplained">caching</a> for a higher-level
* explanation.
*
* @param <K> the base key type for all caches created by this builder
* @param <V> the base value type for all caches created by this builder
* @author Charles Fry
* @author Kevin Bourrillion
* @since 10.0
*/
@GwtCompatible(emulated = true)
public final class CacheBuilder<K, V> {
private static final int DEFAULT_INITIAL_CAPACITY = 16;
private static final int DEFAULT_CONCURRENCY_LEVEL = 4;
private static final int DEFAULT_EXPIRATION_NANOS = 0;
private static final int DEFAULT_REFRESH_NANOS = 0;
static final Supplier<? extends StatsCounter> NULL_STATS_COUNTER = Suppliers.ofInstance(
new StatsCounter() {
@Override
public void recordHits(int count) {}
@Override
public void recordMisses(int count) {}
@Override
public void recordLoadSuccess(long loadTime) {}
@Override
public void recordLoadException(long loadTime) {}
@Override
public void recordEviction() {}
@Override
public CacheStats snapshot() {
return EMPTY_STATS;
}
});
static final CacheStats EMPTY_STATS = new CacheStats(0, 0, 0, 0, 0, 0);
static final Supplier<StatsCounter> CACHE_STATS_COUNTER =
new Supplier<StatsCounter>() {
@Override
public StatsCounter get() {
return new SimpleStatsCounter();
}
};
enum NullListener implements RemovalListener<Object, Object> {
INSTANCE;
@Override
public void onRemoval(RemovalNotification<Object, Object> notification) {}
}
enum OneWeigher implements Weigher<Object, Object> {
INSTANCE;
@Override
public int weigh(Object key, Object value) {
return 1;
}
}
static final Ticker NULL_TICKER = new Ticker() {
@Override
public long read() {
return 0;
}
};
private static final Logger logger = Logger.getLogger(CacheBuilder.class.getName());
static final int UNSET_INT = -1;
boolean strictParsing = true;
int initialCapacity = UNSET_INT;
int concurrencyLevel = UNSET_INT;
long maximumSize = UNSET_INT;
long maximumWeight = UNSET_INT;
Weigher<? super K, ? super V> weigher;
Strength keyStrength;
Strength valueStrength;
long expireAfterWriteNanos = UNSET_INT;
long expireAfterAccessNanos = UNSET_INT;
long refreshNanos = UNSET_INT;
Equivalence<Object> keyEquivalence;
Equivalence<Object> valueEquivalence;
RemovalListener<? super K, ? super V> removalListener;
Ticker ticker;
Supplier<? extends StatsCounter> statsCounterSupplier = NULL_STATS_COUNTER;
// TODO(fry): make constructor private and update tests to use newBuilder
CacheBuilder() {}
/**
* Constructs a new {@code CacheBuilder} instance with default settings, including strong keys,
* strong values, and no automatic eviction of any kind.
*/
public static CacheBuilder<Object, Object> newBuilder() {
return new CacheBuilder<Object, Object>();
}
/**
* Constructs a new {@code CacheBuilder} instance with the settings specified in {@code spec}.
*
* @since 12.0
*/
@Beta
@GwtIncompatible("To be supported")
public static CacheBuilder<Object, Object> from(CacheBuilderSpec spec) {
return spec.toCacheBuilder()
.lenientParsing();
}
/**
* Constructs a new {@code CacheBuilder} instance with the settings specified in {@code spec}.
* This is especially useful for command-line configuration of a {@code CacheBuilder}.
*
* @param spec a String in the format specified by {@link CacheBuilderSpec}
* @since 12.0
*/
@Beta
@GwtIncompatible("To be supported")
public static CacheBuilder<Object, Object> from(String spec) {
return from(CacheBuilderSpec.parse(spec));
}
/**
* Enables lenient parsing. Useful for tests and spec parsing.
*/
@GwtIncompatible("To be supported")
CacheBuilder<K, V> lenientParsing() {
strictParsing = false;
return this;
}
/**
* Sets a custom {@code Equivalence} strategy for comparing keys.
*
* <p>By default, the cache uses {@link Equivalence#identity} to determine key equality when
* {@link #weakKeys} is specified, and {@link Equivalence#equals()} otherwise.
*/
@GwtIncompatible("To be supported")
CacheBuilder<K, V> keyEquivalence(Equivalence<Object> equivalence) {
checkState(keyEquivalence == null, "key equivalence was already set to %s", keyEquivalence);
keyEquivalence = checkNotNull(equivalence);
return this;
}
Equivalence<Object> getKeyEquivalence() {
return MoreObjects.firstNonNull(keyEquivalence, getKeyStrength().defaultEquivalence());
}
/**
* Sets a custom {@code Equivalence} strategy for comparing values.
*
* <p>By default, the cache uses {@link Equivalence#identity} to determine value equality when
* {@link #weakValues} or {@link #softValues} is specified, and {@link Equivalence#equals()}
* otherwise.
*/
@GwtIncompatible("To be supported")
CacheBuilder<K, V> valueEquivalence(Equivalence<Object> equivalence) {
checkState(valueEquivalence == null,
"value equivalence was already set to %s", valueEquivalence);
this.valueEquivalence = checkNotNull(equivalence);
return this;
}
Equivalence<Object> getValueEquivalence() {
return MoreObjects.firstNonNull(valueEquivalence, getValueStrength().defaultEquivalence());
}
/**
* Sets the minimum total size for the internal hash tables. For example, if the initial capacity
* is {@code 60}, and the concurrency level is {@code 8}, then eight segments are created, each
* having a hash table of size eight. Providing a large enough estimate at construction time
* avoids the need for expensive resizing operations later, but setting this value unnecessarily
* high wastes memory.
*
* @throws IllegalArgumentException if {@code initialCapacity} is negative
* @throws IllegalStateException if an initial capacity was already set
*/
public CacheBuilder<K, V> initialCapacity(int initialCapacity) {
checkState(this.initialCapacity == UNSET_INT, "initial capacity was already set to %s",
this.initialCapacity);
checkArgument(initialCapacity >= 0);
this.initialCapacity = initialCapacity;
return this;
}
int getInitialCapacity() {
return (initialCapacity == UNSET_INT) ? DEFAULT_INITIAL_CAPACITY : initialCapacity;
}
/**
* Guides the allowed concurrency among update operations. Used as a hint for internal sizing. The
* table is internally partitioned to try to permit the indicated number of concurrent updates
* without contention. Because assignment of entries to these partitions is not necessarily
* uniform, the actual concurrency observed may vary. Ideally, you should choose a value to
* accommodate as many threads as will ever concurrently modify the table. Using a significantly
* higher value than you need can waste space and time, and a significantly lower value can lead
* to thread contention. But overestimates and underestimates within an order of magnitude do not
* usually have much noticeable impact. A value of one permits only one thread to modify the cache
* at a time, but since read operations and cache loading computations can proceed concurrently,
* this still yields higher concurrency than full synchronization.
*
* <p> Defaults to 4. <b>Note:</b>The default may change in the future. If you care about this
* value, you should always choose it explicitly.
*
* <p>The current implementation uses the concurrency level to create a fixed number of hashtable
* segments, each governed by its own write lock. The segment lock is taken once for each explicit
* write, and twice for each cache loading computation (once prior to loading the new value,
* and once after loading completes). Much internal cache management is performed at the segment
* granularity. For example, access queues and write queues are kept per segment when they are
* required by the selected eviction algorithm. As such, when writing unit tests it is not
* uncommon to specify {@code concurrencyLevel(1)} in order to achieve more deterministic eviction
* behavior.
*
* <p>Note that future implementations may abandon segment locking in favor of more advanced
* concurrency controls.
*
* @throws IllegalArgumentException if {@code concurrencyLevel} is nonpositive
* @throws IllegalStateException if a concurrency level was already set
*/
public CacheBuilder<K, V> concurrencyLevel(int concurrencyLevel) {
checkState(this.concurrencyLevel == UNSET_INT, "concurrency level was already set to %s",
this.concurrencyLevel);
checkArgument(concurrencyLevel > 0);
this.concurrencyLevel = concurrencyLevel;
return this;
}
int getConcurrencyLevel() {
return (concurrencyLevel == UNSET_INT) ? DEFAULT_CONCURRENCY_LEVEL : concurrencyLevel;
}
/**
* Specifies the maximum number of entries the cache may contain. Note that the cache <b>may evict
* an entry before this limit is exceeded</b>. As the cache size grows close to the maximum, the
* cache evicts entries that are less likely to be used again. For example, the cache may evict an
* entry because it hasn't been used recently or very often.
*
* <p>When {@code size} is zero, elements will be evicted immediately after being loaded into the
* cache. This can be useful in testing, or to disable caching temporarily without a code change.
*
* <p>This feature cannot be used in conjunction with {@link #maximumWeight}.
*
* @param size the maximum size of the cache
* @throws IllegalArgumentException if {@code size} is negative
* @throws IllegalStateException if a maximum size or weight was already set
*/
public CacheBuilder<K, V> maximumSize(long size) {
checkState(this.maximumSize == UNSET_INT, "maximum size was already set to %s",
this.maximumSize);
checkState(this.maximumWeight == UNSET_INT, "maximum weight was already set to %s",
this.maximumWeight);
checkState(this.weigher == null, "maximum size can not be combined with weigher");
checkArgument(size >= 0, "maximum size must not be negative");
this.maximumSize = size;
return this;
}
/**
* Specifies the maximum weight of entries the cache may contain. Weight is determined using the
* {@link Weigher} specified with {@link #weigher}, and use of this method requires a
* corresponding call to {@link #weigher} prior to calling {@link #build}.
*
* <p>Note that the cache <b>may evict an entry before this limit is exceeded</b>. As the cache
* size grows close to the maximum, the cache evicts entries that are less likely to be used
* again. For example, the cache may evict an entry because it hasn't been used recently or very
* often.
*
* <p>When {@code weight} is zero, elements will be evicted immediately after being loaded into
* cache. This can be useful in testing, or to disable caching temporarily without a code
* change.
*
* <p>Note that weight is only used to determine whether the cache is over capacity; it has no
* effect on selecting which entry should be evicted next.
*
* <p>This feature cannot be used in conjunction with {@link #maximumSize}.
*
* @param weight the maximum total weight of entries the cache may contain
* @throws IllegalArgumentException if {@code weight} is negative
* @throws IllegalStateException if a maximum weight or size was already set
* @since 11.0
*/
@GwtIncompatible("To be supported")
public CacheBuilder<K, V> maximumWeight(long weight) {
checkState(this.maximumWeight == UNSET_INT, "maximum weight was already set to %s",
this.maximumWeight);
checkState(this.maximumSize == UNSET_INT, "maximum size was already set to %s",
this.maximumSize);
this.maximumWeight = weight;
checkArgument(weight >= 0, "maximum weight must not be negative");
return this;
}
/**
* Specifies the weigher to use in determining the weight of entries. Entry weight is taken
* into consideration by {@link #maximumWeight(long)} when determining which entries to evict, and
* use of this method requires a corresponding call to {@link #maximumWeight(long)} prior to
* calling {@link #build}. Weights are measured and recorded when entries are inserted into the
* cache, and are thus effectively static during the lifetime of a cache entry.
*
* <p>When the weight of an entry is zero it will not be considered for size-based eviction
* (though it still may be evicted by other means).
*
* <p><b>Important note:</b> Instead of returning <em>this</em> as a {@code CacheBuilder}
* instance, this method returns {@code CacheBuilder<K1, V1>}. From this point on, either the
* original reference or the returned reference may be used to complete configuration and build
* the cache, but only the "generic" one is type-safe. That is, it will properly prevent you from
* building caches whose key or value types are incompatible with the types accepted by the
* weigher already provided; the {@code CacheBuilder} type cannot do this. For best results,
* simply use the standard method-chaining idiom, as illustrated in the documentation at top,
* configuring a {@code CacheBuilder} and building your {@link Cache} all in a single statement.
*
* <p><b>Warning:</b> if you ignore the above advice, and use this {@code CacheBuilder} to build
* a cache whose key or value type is incompatible with the weigher, you will likely experience
* a {@link ClassCastException} at some <i>undefined</i> point in the future.
*
* @param weigher the weigher to use in calculating the weight of cache entries
* @throws IllegalArgumentException if {@code size} is negative
* @throws IllegalStateException if a maximum size was already set
* @since 11.0
*/
@GwtIncompatible("To be supported")
public <K1 extends K, V1 extends V> CacheBuilder<K1, V1> weigher(
Weigher<? super K1, ? super V1> weigher) {
checkState(this.weigher == null);
if (strictParsing) {
checkState(this.maximumSize == UNSET_INT, "weigher can not be combined with maximum size",
this.maximumSize);
}
// safely limiting the kinds of caches this can produce
@SuppressWarnings("unchecked")
CacheBuilder<K1, V1> me = (CacheBuilder<K1, V1>) this;
me.weigher = checkNotNull(weigher);
return me;
}
long getMaximumWeight() {
if (expireAfterWriteNanos == 0 || expireAfterAccessNanos == 0) {
return 0;
}
return (weigher == null) ? maximumSize : maximumWeight;
}
// Make a safe contravariant cast now so we don't have to do it over and over.
@SuppressWarnings("unchecked")
<K1 extends K, V1 extends V> Weigher<K1, V1> getWeigher() {
return (Weigher<K1, V1>) MoreObjects.firstNonNull(weigher, OneWeigher.INSTANCE);
}
/**
* Specifies that each key (not value) stored in the cache should be wrapped in a {@link
* WeakReference} (by default, strong references are used).
*
* <p><b>Warning:</b> when this method is used, the resulting cache will use identity ({@code ==})
* comparison to determine equality of keys.
*
* <p>Entries with keys that have been garbage collected may be counted in {@link Cache#size},
* but will never be visible to read or write operations; such entries are cleaned up as part of
* the routine maintenance described in the class javadoc.
*
* @throws IllegalStateException if the key strength was already set
*/
@GwtIncompatible("java.lang.ref.WeakReference")
public CacheBuilder<K, V> weakKeys() {
return setKeyStrength(Strength.WEAK);
}
CacheBuilder<K, V> setKeyStrength(Strength strength) {
checkState(keyStrength == null, "Key strength was already set to %s", keyStrength);
keyStrength = checkNotNull(strength);
return this;
}
Strength getKeyStrength() {
return MoreObjects.firstNonNull(keyStrength, Strength.STRONG);
}
/**
* Specifies that each value (not key) stored in the cache should be wrapped in a
* {@link WeakReference} (by default, strong references are used).
*
* <p>Weak values will be garbage collected once they are weakly reachable. This makes them a poor
* candidate for caching; consider {@link #softValues} instead.
*
* <p><b>Note:</b> when this method is used, the resulting cache will use identity ({@code ==})
* comparison to determine equality of values.
*
* <p>Entries with values that have been garbage collected may be counted in {@link Cache#size},
* but will never be visible to read or write operations; such entries are cleaned up as part of
* the routine maintenance described in the class javadoc.
*
* @throws IllegalStateException if the value strength was already set
*/
@GwtIncompatible("java.lang.ref.WeakReference")
public CacheBuilder<K, V> weakValues() {
return setValueStrength(Strength.WEAK);
}
/**
* Specifies that each value (not key) stored in the cache should be wrapped in a
* {@link SoftReference} (by default, strong references are used). Softly-referenced objects will
* be garbage-collected in a <i>globally</i> least-recently-used manner, in response to memory
* demand.
*
* <p><b>Warning:</b> in most circumstances it is better to set a per-cache {@linkplain
* #maximumSize(long) maximum size} instead of using soft references. You should only use this
* method if you are well familiar with the practical consequences of soft references.
*
* <p><b>Note:</b> when this method is used, the resulting cache will use identity ({@code ==})
* comparison to determine equality of values.
*
* <p>Entries with values that have been garbage collected may be counted in {@link Cache#size},
* but will never be visible to read or write operations; such entries are cleaned up as part of
* the routine maintenance described in the class javadoc.
*
* @throws IllegalStateException if the value strength was already set
*/
@GwtIncompatible("java.lang.ref.SoftReference")
public CacheBuilder<K, V> softValues() {
return setValueStrength(Strength.SOFT);
}
CacheBuilder<K, V> setValueStrength(Strength strength) {
checkState(valueStrength == null, "Value strength was already set to %s", valueStrength);
valueStrength = checkNotNull(strength);
return this;
}
Strength getValueStrength() {
return MoreObjects.firstNonNull(valueStrength, Strength.STRONG);
}
/**
* Specifies that each entry should be automatically removed from the cache once a fixed duration
* has elapsed after the entry's creation, or the most recent replacement of its value.
*
* <p>When {@code duration} is zero, this method hands off to
* {@link #maximumSize(long) maximumSize}{@code (0)}, ignoring any otherwise-specificed maximum
* size or weight. This can be useful in testing, or to disable caching temporarily without a code
* change.
*
* <p>Expired entries may be counted in {@link Cache#size}, but will never be visible to read or
* write operations. Expired entries are cleaned up as part of the routine maintenance described
* in the class javadoc.
*
* @param duration the length of time after an entry is created that it should be automatically
* removed
* @param unit the unit that {@code duration} is expressed in
* @throws IllegalArgumentException if {@code duration} is negative
* @throws IllegalStateException if the time to live or time to idle was already set
*/
public CacheBuilder<K, V> expireAfterWrite(long duration, TimeUnit unit) {
checkState(expireAfterWriteNanos == UNSET_INT, "expireAfterWrite was already set to %s ns",
expireAfterWriteNanos);
checkArgument(duration >= 0, "duration cannot be negative: %s %s", duration, unit);
this.expireAfterWriteNanos = unit.toNanos(duration);
return this;
}
long getExpireAfterWriteNanos() {
return (expireAfterWriteNanos == UNSET_INT) ? DEFAULT_EXPIRATION_NANOS : expireAfterWriteNanos;
}
/**
* Specifies that each entry should be automatically removed from the cache once a fixed duration
* has elapsed after the entry's creation, the most recent replacement of its value, or its last
* access. Access time is reset by all cache read and write operations (including
* {@code Cache.asMap().get(Object)} and {@code Cache.asMap().put(K, V)}), but not by operations
* on the collection-views of {@link Cache#asMap}.
*
* <p>When {@code duration} is zero, this method hands off to
* {@link #maximumSize(long) maximumSize}{@code (0)}, ignoring any otherwise-specificed maximum
* size or weight. This can be useful in testing, or to disable caching temporarily without a code
* change.
*
* <p>Expired entries may be counted in {@link Cache#size}, but will never be visible to read or
* write operations. Expired entries are cleaned up as part of the routine maintenance described
* in the class javadoc.
*
* @param duration the length of time after an entry is last accessed that it should be
* automatically removed
* @param unit the unit that {@code duration} is expressed in
* @throws IllegalArgumentException if {@code duration} is negative
* @throws IllegalStateException if the time to idle or time to live was already set
*/
public CacheBuilder<K, V> expireAfterAccess(long duration, TimeUnit unit) {
checkState(expireAfterAccessNanos == UNSET_INT, "expireAfterAccess was already set to %s ns",
expireAfterAccessNanos);
checkArgument(duration >= 0, "duration cannot be negative: %s %s", duration, unit);
this.expireAfterAccessNanos = unit.toNanos(duration);
return this;
}
long getExpireAfterAccessNanos() {
return (expireAfterAccessNanos == UNSET_INT)
? DEFAULT_EXPIRATION_NANOS : expireAfterAccessNanos;
}
/**
* Specifies that active entries are eligible for automatic refresh once a fixed duration has
* elapsed after the entry's creation, or the most recent replacement of its value. The semantics
* of refreshes are specified in {@link LoadingCache#refresh}, and are performed by calling
* {@link CacheLoader#reload}.
*
* <p>As the default implementation of {@link CacheLoader#reload} is synchronous, it is
* recommended that users of this method override {@link CacheLoader#reload} with an asynchronous
* implementation; otherwise refreshes will be performed during unrelated cache read and write
* operations.
*
* <p>Currently automatic refreshes are performed when the first stale request for an entry
* occurs. The request triggering refresh will make a blocking call to {@link CacheLoader#reload}
* and immediately return the new value if the returned future is complete, and the old value
* otherwise.
*
* <p><b>Note:</b> <i>all exceptions thrown during refresh will be logged and then swallowed</i>.
*
* @param duration the length of time after an entry is created that it should be considered
* stale, and thus eligible for refresh
* @param unit the unit that {@code duration} is expressed in
* @throws IllegalArgumentException if {@code duration} is negative
* @throws IllegalStateException if the refresh interval was already set
* @since 11.0
*/
@Beta
@GwtIncompatible("To be supported (synchronously).")
public CacheBuilder<K, V> refreshAfterWrite(long duration, TimeUnit unit) {
checkNotNull(unit);
checkState(refreshNanos == UNSET_INT, "refresh was already set to %s ns", refreshNanos);
checkArgument(duration > 0, "duration must be positive: %s %s", duration, unit);
this.refreshNanos = unit.toNanos(duration);
return this;
}
long getRefreshNanos() {
return (refreshNanos == UNSET_INT) ? DEFAULT_REFRESH_NANOS : refreshNanos;
}
/**
* Specifies a nanosecond-precision time source for this cache. By default,
* {@link System#nanoTime} is used.
*
* <p>The primary intent of this method is to facilitate testing of caches with a fake or mock
* time source.
*
* @throws IllegalStateException if a ticker was already set
*/
public CacheBuilder<K, V> ticker(Ticker ticker) {
checkState(this.ticker == null);
this.ticker = checkNotNull(ticker);
return this;
}
Ticker getTicker(boolean recordsTime) {
if (ticker != null) {
return ticker;
}
return recordsTime ? Ticker.systemTicker() : NULL_TICKER;
}
/**
* Specifies a listener instance that caches should notify each time an entry is removed for any
* {@linkplain RemovalCause reason}. Each cache created by this builder will invoke this listener
* as part of the routine maintenance described in the class documentation above.
*
* <p><b>Warning:</b> after invoking this method, do not continue to use <i>this</i> cache
* builder reference; instead use the reference this method <i>returns</i>. At runtime, these
* point to the same instance, but only the returned reference has the correct generic type
* information so as to ensure type safety. For best results, use the standard method-chaining
* idiom illustrated in the class documentation above, configuring a builder and building your
* cache in a single statement. Failure to heed this advice can result in a {@link
* ClassCastException} being thrown by a cache operation at some <i>undefined</i> point in the
* future.
*
* <p><b>Warning:</b> any exception thrown by {@code listener} will <i>not</i> be propagated to
* the {@code Cache} user, only logged via a {@link Logger}.
*
* @return the cache builder reference that should be used instead of {@code this} for any
* remaining configuration and cache building
* @throws IllegalStateException if a removal listener was already set
*/
@CheckReturnValue
public <K1 extends K, V1 extends V> CacheBuilder<K1, V1> removalListener(
RemovalListener<? super K1, ? super V1> listener) {
checkState(this.removalListener == null);
// safely limiting the kinds of caches this can produce
@SuppressWarnings("unchecked")
CacheBuilder<K1, V1> me = (CacheBuilder<K1, V1>) this;
me.removalListener = checkNotNull(listener);
return me;
}
// Make a safe contravariant cast now so we don't have to do it over and over.
@SuppressWarnings("unchecked")
<K1 extends K, V1 extends V> RemovalListener<K1, V1> getRemovalListener() {
return (RemovalListener<K1, V1>)
MoreObjects.firstNonNull(removalListener, NullListener.INSTANCE);
}
/**
* Enable the accumulation of {@link CacheStats} during the operation of the cache. Without this
* {@link Cache#stats} will return zero for all statistics. Note that recording stats requires
* bookkeeping to be performed with each operation, and thus imposes a performance penalty on
* cache operation.
*
* @since 12.0 (previously, stats collection was automatic)
*/
public CacheBuilder<K, V> recordStats() {
statsCounterSupplier = CACHE_STATS_COUNTER;
return this;
}
boolean isRecordingStats() {
return statsCounterSupplier == CACHE_STATS_COUNTER;
}
Supplier<? extends StatsCounter> getStatsCounterSupplier() {
return statsCounterSupplier;
}
/**
* Builds a cache, which either returns an already-loaded value for a given key or atomically
* computes or retrieves it using the supplied {@code CacheLoader}. If another thread is currently
* loading the value for this key, simply waits for that thread to finish and returns its
* loaded value. Note that multiple threads can concurrently load values for distinct keys.
*
* <p>This method does not alter the state of this {@code CacheBuilder} instance, so it can be
* invoked again to create multiple independent caches.
*
* @param loader the cache loader used to obtain new values
* @return a cache having the requested features
*/
public <K1 extends K, V1 extends V> LoadingCache<K1, V1> build(
CacheLoader<? super K1, V1> loader) {
checkWeightWithWeigher();
return new LocalCache.LocalLoadingCache<K1, V1>(this, loader);
}
/**
* Builds a cache which does not automatically load values when keys are requested.
*
* <p>Consider {@link #build(CacheLoader)} instead, if it is feasible to implement a
* {@code CacheLoader}.
*
* <p>This method does not alter the state of this {@code CacheBuilder} instance, so it can be
* invoked again to create multiple independent caches.
*
* @return a cache having the requested features
* @since 11.0
*/
public <K1 extends K, V1 extends V> Cache<K1, V1> build() {
checkWeightWithWeigher();
checkNonLoadingCache();
return new LocalCache.LocalManualCache<K1, V1>(this);
}
private void checkNonLoadingCache() {
checkState(refreshNanos == UNSET_INT, "refreshAfterWrite requires a LoadingCache");
}
private void checkWeightWithWeigher() {
if (weigher == null) {
checkState(maximumWeight == UNSET_INT, "maximumWeight requires weigher");
} else {
if (strictParsing) {
checkState(maximumWeight != UNSET_INT, "weigher requires maximumWeight");
} else {
if (maximumWeight == UNSET_INT) {
logger.log(Level.WARNING, "ignoring weigher specified without maximumWeight");
}
}
}
}
/**
* Returns a string representation for this CacheBuilder instance. The exact form of the returned
* string is not specified.
*/
@Override
public String toString() {
MoreObjects.ToStringHelper s = MoreObjects.toStringHelper(this);
if (initialCapacity != UNSET_INT) {
s.add("initialCapacity", initialCapacity);
}
if (concurrencyLevel != UNSET_INT) {
s.add("concurrencyLevel", concurrencyLevel);
}
if (maximumSize != UNSET_INT) {
s.add("maximumSize", maximumSize);
}
if (maximumWeight != UNSET_INT) {
s.add("maximumWeight", maximumWeight);
}
if (expireAfterWriteNanos != UNSET_INT) {
s.add("expireAfterWrite", expireAfterWriteNanos + "ns");
}
if (expireAfterAccessNanos != UNSET_INT) {
s.add("expireAfterAccess", expireAfterAccessNanos + "ns");
}
if (keyStrength != null) {
s.add("keyStrength", Ascii.toLowerCase(keyStrength.toString()));
}
if (valueStrength != null) {
s.add("valueStrength", Ascii.toLowerCase(valueStrength.toString()));
}
if (keyEquivalence != null) {
s.addValue("keyEquivalence");
}
if (valueEquivalence != null) {
s.addValue("valueEquivalence");
}
if (removalListener != null) {
s.addValue("removalListener");
}
return s.toString();
}
}