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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 java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.conqat.lib.commons.cache4j.backend.ICacheBackend;
import org.conqat.lib.commons.error.NeverThrownRuntimeException;
import org.conqat.lib.commons.factory.IParameterizedFactory;
/**
* Implementation of a cache that manages a separate backend for each thread, thus isolating threads
* from each other. Note that accessing this cache from many temporary threads can lead to memory
* leaks (as the cached data is still stored) for certain backends.
*
* @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 ThreadLocalCache implements ICache {
/** The name of this cache (used for reporting). */
private final String name;
/** The factory used to obtain elements. */
private final IParameterizedFactory factory;
/** The backend used. */
private final ICacheBackend backend;
/** Stores all sub caches for reporting. */
private final List> subCaches = Collections
.synchronizedList(new ArrayList>());
/** Manages the individual caches for each thread. */
private final ThreadLocal> localCaches = new ThreadLocal>() {
/** {@inheritDoc} */
@Override
protected BasicCache initialValue() {
BasicCache cache = new BasicCache<>(name + ":" + Thread.currentThread().getId(), factory,
backend.newInstance());
subCaches.add(cache);
return cache;
}
};
/**
* Constructor.
*
* @param factory
* the factory has to either support multi-threaded access or to be synchronized!
*/
public ThreadLocalCache(String name, IParameterizedFactory factory, ICacheBackend backend) {
this.name = name;
this.factory = factory;
this.backend = backend;
}
/** {@inheritDoc} */
@Override
public V obtain(K parameter) throws X {
return localCaches.get().obtain(parameter);
}
/** {@inheritDoc} */
@Override
public void clear(boolean allThreads) {
if (allThreads) {
for (BasicCache cache : subCaches) {
cache.clear(false);
}
} else {
localCaches.get().clear(false);
}
}
/** {@inheritDoc} */
@Override
public String getName() {
return name;
}
/** {@inheritDoc} */
@Override
public int getHits() {
int result = 0;
for (BasicCache cache : subCaches) {
result += cache.getHits();
}
return result;
}
/** {@inheritDoc} */
@Override
public int getMisses() {
int result = 0;
for (BasicCache cache : subCaches) {
result += cache.getMisses();
}
return result;
}
/** {@inheritDoc} */
@Override
public long getMissCostMillis() {
long result = 0;
for (BasicCache cache : subCaches) {
result += cache.getMissCostMillis();
}
return result;
}
}