org.cache2k.operation.TimeReference Maven / Gradle / Ivy
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package org.cache2k.operation;
/*
* #%L
* cache2k API
* %%
* Copyright (C) 2000 - 2021 headissue GmbH, Munich
* %%
* 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.
* #L%
*/
import org.cache2k.CacheEntry;
import org.cache2k.processor.MutableCacheEntry;
/**
* Time reference for a cache. By default the current time is retrieved with
* {@link System#currentTimeMillis()}. Another time reference can be specified
* if the application uses a different time source or when a simulated clock should be used.
*
* An instance may implement {@link AutoCloseable} if resources need to be cleaned up.
*
* @author Jens Wilke
*/
public interface TimeReference {
/**
* Default implementation using {@link System#currentTimeMillis()} as time reference.
*/
final TimeReference DEFAULT = new TimeReference() {
@Override
public long millis() {
return System.currentTimeMillis();
}
@Override
public void sleep(long millis) throws InterruptedException {
Thread.sleep(millis);
}
};
/**
* Returns the milliseconds since epoch. In the simulated clock a call to this method
* would make time pass in small increments.
*
*
It is possible to use other time scales and references (e.g. nano seconds). In
* this case the method {@link #toMillis(long)} needs to be implemented. All times in the
* cache API, e.g. {@link MutableCacheEntry#getExpiryTime()} or in
* {@link org.cache2k.io.AdvancedCacheLoader#load(Object, long, CacheEntry)} are based on the
* time defined here.
*/
long millis();
/**
* Wait for the specified amount of time in milliseconds.
*
*
The value of 0 means that the thread should pause and other processing should be
* done. In a simulated clock this would wait for concurrent processing and, if
* no processing is happening, advance the time to the next event.
*/
void sleep(long millis) throws InterruptedException;
/**
* Convert a value returned by {@link #millis()} to milliseconds since epoch.
* This can be overridden in case another time scale and or reference is used.
* Conversion is needed for correctly scheduling timer task that regularly process
* the expiry tasks.
*/
default long toMillis(long millis) {
return millis;
}
}