org.springframework.cache.support.AbstractCacheManager Maven / Gradle / Ivy
/*
* Copyright 2002-2015 the original author or 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 org.springframework.cache.support;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.cache.Cache;
import org.springframework.cache.CacheManager;
/**
* Abstract base class implementing the common {@link CacheManager} methods.
* Useful for 'static' environments where the backing caches do not change.
*
* @author Costin Leau
* @author Juergen Hoeller
* @author Stephane Nicoll
* @since 3.1
*/
public abstract class AbstractCacheManager implements CacheManager, InitializingBean {
private final ConcurrentMap cacheMap = new ConcurrentHashMap(16);
private volatile Set cacheNames = Collections.emptySet();
// Early cache initialization on startup
@Override
public void afterPropertiesSet() {
initializeCaches();
}
/**
* Initialize the static configuration of caches.
* Triggered on startup through {@link #afterPropertiesSet()};
* can also be called to re-initialize at runtime.
* @since 4.2.2
* @see #loadCaches()
*/
public void initializeCaches() {
Collection caches = loadCaches();
synchronized (this.cacheMap) {
this.cacheNames = Collections.emptySet();
this.cacheMap.clear();
Set cacheNames = new LinkedHashSet(caches.size());
for (Cache cache : caches) {
String name = cache.getName();
this.cacheMap.put(name, decorateCache(cache));
cacheNames.add(name);
}
this.cacheNames = Collections.unmodifiableSet(cacheNames);
}
}
/**
* Load the initial caches for this cache manager.
* Called by {@link #afterPropertiesSet()} on startup.
* The returned collection may be empty but must not be {@code null}.
*/
protected abstract Collection loadCaches();
// Lazy cache initialization on access
@Override
public Cache getCache(String name) {
Cache cache = this.cacheMap.get(name);
if (cache != null) {
return cache;
}
else {
// Fully synchronize now for missing cache creation...
synchronized (this.cacheMap) {
cache = this.cacheMap.get(name);
if (cache == null) {
cache = getMissingCache(name);
if (cache != null) {
cache = decorateCache(cache);
this.cacheMap.put(name, cache);
updateCacheNames(name);
}
}
return cache;
}
}
}
@Override
public Collection getCacheNames() {
return this.cacheNames;
}
// Common cache initialization delegates for subclasses
/**
* Check for a registered cache of the given name.
* In contrast to {@link #getCache(String)}, this method does not trigger
* the lazy creation of missing caches via {@link #getMissingCache(String)}.
* @param name the cache identifier (must not be {@code null})
* @return the associated Cache instance, or {@code null} if none found
* @since 4.1
* @see #getCache(String)
* @see #getMissingCache(String)
*/
protected final Cache lookupCache(String name) {
return this.cacheMap.get(name);
}
/**
* Dynamically register an additional Cache with this manager.
* @param cache the Cache to register
*/
protected final void addCache(Cache cache) {
String name = cache.getName();
synchronized (this.cacheMap) {
if (this.cacheMap.put(name, decorateCache(cache)) == null) {
updateCacheNames(name);
}
}
}
/**
* Update the exposed {@link #cacheNames} set with the given name.
* This will always be called within a full {@link #cacheMap} lock
* and effectively behaves like a {@code CopyOnWriteArraySet} with
* preserved order but exposed as an unmodifiable reference.
* @param name the name of the cache to be added
*/
private void updateCacheNames(String name) {
Set cacheNames = new LinkedHashSet(this.cacheNames.size() + 1);
cacheNames.addAll(this.cacheNames);
cacheNames.add(name);
this.cacheNames = Collections.unmodifiableSet(cacheNames);
}
// Overridable template methods for cache initialization
/**
* Decorate the given Cache object if necessary.
* @param cache the Cache object to be added to this CacheManager
* @return the decorated Cache object to be used instead,
* or simply the passed-in Cache object by default
*/
protected Cache decorateCache(Cache cache) {
return cache;
}
/**
* Return a missing cache with the specified {@code name} or {@code null} if
* such cache does not exist or could not be created on the fly.
* Some caches may be created at runtime in the native provided. If a lookup
* by name does not yield any result, a subclass gets a chance to register
* such a cache at runtime. The returned cache will be automatically added to
* this instance.
* @param name the name of the cache to retrieve
* @return the missing cache or {@code null} if no such cache exists or could be
* created
* @since 4.1
* @see #getCache(String)
*/
protected Cache getMissingCache(String name) {
return null;
}
}