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This is the ehcache core module. Pair it with other modules for added functionality.
/**
* Copyright 2003-2009 Terracotta, Inc.
*
* 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 net.sf.ehcache.management;
import net.sf.ehcache.CacheException;
import net.sf.ehcache.Ehcache;
import net.sf.ehcache.Statistics;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import java.io.Serializable;
/**
* A JMX CacheStatistics decorator for an ehcache Statistics class.
*
* An immutable Cache statistics implementation}
*
* This is like a value object, with the added ability to clear cache statistics on the cache.
* That ability does not survive any Serialization of this class. On deserialization the cache
* can be considered disconnected.
*
* The accuracy of these statistics are determined by the value of {#getStatisticsAccuracy()}
* at the time the statistic was computed. This can be changed by setting {@link net.sf.ehcache.Cache#setStatisticsAccuracy}.
*
* Because this class maintains a reference to an Ehcache, any references held to this class will precent the Ehcache
* from getting garbage collected.
*
* @author Greg Luck
* @version $Id: CacheStatistics.java 1012 2009-08-20 04:23:00Z gregluck $
* @since 1.3
*/
public class CacheStatistics implements CacheStatisticsMBean, Serializable {
private static final long serialVersionUID = 8085302752781762030L;
private transient Ehcache ehcache;
private Statistics statistics;
private ObjectName objectName;
private long lastUpdated;
/**
* Constructs an object from an ehcache statistics object
*
* @param ehcache the backing ehcache
*/
public CacheStatistics(Ehcache ehcache) {
this.ehcache = ehcache;
objectName = createObjectName(ehcache.getCacheManager().getName(),
ehcache.getName());
}
/**
* Creates an object name using the scheme "net.sf.ehcache:type=CacheStatistics,CacheManager=,name="
*/
static ObjectName createObjectName(String cacheManagerName, String cacheName) {
ObjectName objectName;
try {
objectName = new ObjectName("net.sf.ehcache:type=CacheStatistics,CacheManager="
+ cacheManagerName + ",name=" + cacheName);
} catch (MalformedObjectNameException e) {
throw new CacheException(e);
}
return objectName;
}
/**
* Accurately measuring statistics can be expensive. Returns the current accuracy setting used
* in the creation of these statistics.
*
* @return one of {@link Statistics#STATISTICS_ACCURACY_BEST_EFFORT}, {@link Statistics#STATISTICS_ACCURACY_GUARANTEED}, {@link Statistics#STATISTICS_ACCURACY_NONE}
*/
public int getStatisticsAccuracy() {
updateIfNeeded();
return statistics.getStatisticsAccuracy();
}
private void updateIfNeeded() {
if (System.currentTimeMillis() != lastUpdated) {
statistics = ehcache.getStatistics();
lastUpdated = System.currentTimeMillis();
}
}
/**
* Accurately measuring statistics can be expensive. Returns the current accuracy setting.
*
* @return a human readable description of the accuracy setting. One of "None", "Best Effort" or "Guaranteed".
*/
public String getStatisticsAccuracyDescription() {
updateIfNeeded();
return statistics.getStatisticsAccuracyDescription();
}
/**
* @return the name of the Ehcache, or null is there no associated cache
*/
public String getAssociatedCacheName() {
if (statistics == null) {
return null;
} else {
return statistics.getAssociatedCacheName();
}
}
/**
* Clears the statistic counters to 0 for the associated Cache.
*/
public void clearStatistics() {
statistics.clearStatistics();
}
/**
* The number of times a requested item was found in the cache.
*
* Warning. This statistic is recorded as a long. If the statistic is large than Integer#MAX_VALUE
* precision will be lost.
*
* @return the number of times a requested item was found in the cache
*/
public long getCacheHits() {
updateIfNeeded();
return statistics.getCacheHits();
}
/**
* Number of times a requested item was found in the Memory Store.
*
* @return the number of times a requested item was found in memory
*/
public long getInMemoryHits() {
updateIfNeeded();
return statistics.getInMemoryHits();
}
/**
* Number of times a requested item was found in the Disk Store.
*
* @return the number of times a requested item was found on Disk, or 0 if there is no disk storage configured.
*/
public long getOnDiskHits() {
updateIfNeeded();
return statistics.getOnDiskHits();
}
/**
* Warning. This statistic is recorded as a long. If the statistic is large than Integer#MAX_VALUE
* precision will be lost.
*
* @return the number of times a requested element was not found in the cache
*/
public long getCacheMisses() {
updateIfNeeded();
return statistics.getCacheMisses();
}
/**
* Gets the number of elements stored in the cache. Caclulating this can be expensive. Accordingly,
* this method will return three different values, depending on the statistics accuracy setting.
* Best Effort Size
* This result is returned when the statistics accuracy setting is {@link net.sf.ehcache.Statistics#STATISTICS_ACCURACY_BEST_EFFORT}.
*
* The size is the number of {@link net.sf.ehcache.Element}s in the {@link net.sf.ehcache.store.MemoryStore} plus
* the number of {@link net.sf.ehcache.Element}s in the {@link net.sf.ehcache.store.DiskStore}.
*
* This number is the actual number of elements, including expired elements that have
* not been removed. Any duplicates between stores are accounted for.
*
* Expired elements are removed from the the memory store when
* getting an expired element, or when attempting to spool an expired element to
* disk.
*
* Expired elements are removed from the disk store when getting an expired element,
* or when the expiry thread runs, which is once every five minutes.
*
* Guaranteed Accuracy Size
* This result is returned when the statistics accuracy setting is {@link net.sf.ehcache.Statistics#STATISTICS_ACCURACY_GUARANTEED}.
*
* This method accounts for elements which might be expired or duplicated between stores. It take approximately
* 200ms per 1000 elements to execute.
* Fast but non-accurate Size
* This result is returned when the statistics accuracy setting is {@link Statistics#STATISTICS_ACCURACY_NONE}.
*
* The number given may contain expired elements. In addition if the DiskStore is used it may contain some double
* counting of elements. It takes 6ms for 1000 elements to execute. Time to execute is O(log n). 50,000 elements take
* 36ms.
*
* @return the number of elements in the ehcache, with a varying degree of accuracy, depending on accuracy setting.
*/
public long getObjectCount() {
updateIfNeeded();
return statistics.getObjectCount();
}
/**
* Gets the number of objects in the MemoryStore
* @return the MemoryStore size which is always a count unadjusted for duplicates or expiries
*/
public long getMemoryStoreObjectCount() {
updateIfNeeded();
return statistics.getMemoryStoreObjectCount();
}
/**
* Gets the number of objects in the DiskStore
* @return the DiskStore size which is always a count unadjusted for duplicates or expiries
*/
public long getDiskStoreObjectCount() {
updateIfNeeded();
return statistics.getDiskStoreObjectCount();
}
/**
* @return the object name for this MBean
*/
ObjectName getObjectName() {
return objectName;
}
/**
* Return the backing cache.
* @return the backing cache, if one is connected. On Serialization
* the transient Ehcache reference is dropped.
*/
public Ehcache getEhcache() {
return ehcache;
}
}