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Provides common utility functions
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/*
* Copyright (c) CQSE GmbH
*
* 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.conqat.lib.commons.cache4j;
import org.conqat.lib.commons.cache4j.backend.ICacheBackend;
import org.conqat.lib.commons.error.NeverThrownRuntimeException;
import org.conqat.lib.commons.factory.IParameterizedFactory;
/**
* Basic implementation of a cache.
*
* @param
* the key type. This must have both {@link Object#equals(Object)} and
* {@link Object#hashCode()} correctly implemented.
* @param
* the value type. It is generally recommended to use an immutable type here, but this is
* not required.
* @param
* the type of exception thrown. If no exception will be throws, use
* {@link NeverThrownRuntimeException}.
*/
public class BasicCache implements ICache {
/** The name of this cache (e.g. used for statistics). */
private final String name;
/** The cache backend. */
private ICacheBackend backend;
/** The factory used to create new elements. */
private final IParameterizedFactory factory;
/**
* Counts the number of cache hits. This variable is not synchronized in any way, so multi-threaded
* usage of this class may lead to incorrect results. However, the amount of error is small enough
* to be tolerated, while the performance impact of synchronization is not.
*/
private int hits = 0;
/**
* Counts the number of cache misses. This variable is not synchronized in any way, so
* multi-threaded usage of this class may lead to incorrect results. However, the amount of error is
* small enough to be tolerated, while the performance impact of synchronization is not.
*/
private int misses = 0;
/** Accumulated cost of cache misses in milliseconds. */
private long missCostMillis = 0;
/** Constructor. */
public BasicCache(String name, IParameterizedFactory factory, ICacheBackend backend) {
this.name = name;
this.factory = factory;
this.backend = backend;
}
/** {@inheritDoc} */
@Override
public String getName() {
return name;
}
/** {@inheritDoc} */
@Override
public void clear(boolean allThreads) {
backend = backend.newInstance();
}
/** {@inheritDoc} */
@Override
public V obtain(K key) throws X {
V value = backend.retrieve(key);
if (value != null) {
hits++;
return value;
}
misses++;
long start = System.currentTimeMillis();
value = factory.create(key);
backend.store(key, value);
missCostMillis += System.currentTimeMillis() - start;
return value;
}
/** {@inheritDoc} */
@Override
public int getHits() {
return hits;
}
/** {@inheritDoc} */
@Override
public int getMisses() {
return misses;
}
/** {@inheritDoc} */
@Override
public long getMissCostMillis() {
return missCostMillis;
}
}