org.jivesoftware.util.cache.Cache Maven / Gradle / Ivy
/*
* Copyright (C) 2004-2008 Jive Software. All rights reserved.
*
* 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.jivesoftware.util.cache;
/**
* General purpose cache. It stores objects associated with unique keys in
* memory for fast access. All keys and values added to the cache must
* implement the Serializable interface. Values may implement the Cacheable
* interface, which allows the cache to determine object size much more quickly.
* These restrictions allow a cache to never grow larger than a specified number
* of bytes and to optionally be distributed over a cluster of servers.
*
* If the cache does grow too large, objects will be removed such that those
* that are accessed least frequently are removed first. Because expiration
* happens automatically, the cache makes no guarantee as to how long
* an object will remain in cache after it is put in.
*
* Optionally, a maximum lifetime for all objects can be specified. In that
* case, objects will be deleted from cache after that amount of time, even
* if they are frequently accessed. This feature is useful if objects put in
* cache represent data that should be periodically refreshed; for example,
* information from a database.
*
* All cache operations are thread safe.
*
* Note that neither keys or values can be null; A {@link NullPointerException}
* will be thrown attempting to place or retrieve null values in to the cache.
*
* @see Cacheable
*/
public interface Cache extends java.util.Map {
/**
* Returns the name of the cache.
*
* @return the name of the cache.
*/
String getName();
/**
* Sets the name of the cache
*
* @param name the name of the cache
*/
void setName(String name);
/**
* Returns the maximum size of the cache in bytes. If the cache grows larger
* than the max size, the least frequently used items will be removed. If
* the max cache size is set to -1, there is no size limit.
*
* @return the maximum size of the cache in bytes.
*/
long getMaxCacheSize();
/**
* Sets the maximum size of the cache in bytes. If the cache grows larger
* than the max size, the least frequently used items will be removed. If
* the max cache size is set to -1, there is no size limit.
*
*Note: If using the Hazelcast clustering plugin, this will not take
* effect until the next time the cache is created
*
* @param maxSize the maximum size of the cache in bytes.
*/
void setMaxCacheSize(int maxSize);
/**
* Returns the maximum number of milliseconds that any object can live
* in cache. Once the specified number of milliseconds passes, the object
* will be automatically expired from cache. If the max lifetime is set
* to -1, then objects never expire.
*
* @return the maximum number of milliseconds before objects are expired.
*/
long getMaxLifetime();
/**
* Sets the maximum number of milliseconds that any object can live
* in cache. Once the specified number of milliseconds passes, the object
* will be automatically expired from cache. If the max lifetime is set
* to -1, then objects never expire.
*
*Note: If using the Hazelcast clustering plugin, this will not take
* effect until the next time the cache is created
*
* @param maxLifetime the maximum number of milliseconds before objects are expired.
*/
void setMaxLifetime(long maxLifetime);
/**
* Returns the size of the cache contents in bytes. This value is only a
* rough approximation, so cache users should expect that actual VM
* memory used by the cache could be significantly higher than the value
* reported by this method.
*
* @return the size of the cache contents in bytes.
*/
int getCacheSize();
/**
* Returns the number of cache hits. A cache hit occurs every
* time the get method is called and the cache contains the requested
* object.
*
* Keeping track of cache hits and misses lets one measure how efficient
* the cache is; the higher the percentage of hits, the more efficient.
*
* @return the number of cache hits.
*/
long getCacheHits();
/**
* Returns the number of cache misses. A cache miss occurs every
* time the get method is called and the cache does not contain the
* requested object.
*
* Keeping track of cache hits and misses lets one measure how efficient
* the cache is; the higher the percentage of hits, the more efficient.
*
* @return the number of cache hits.
*/
long getCacheMisses();
}