org.apache.pulsar.client.util.ObjectCache Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.pulsar.client.util;
import java.time.Clock;
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;
public class ObjectCache implements Supplier {
private final Supplier supplier;
private T cachedInstance;
private final long cacheDurationMillis;
private long lastRefreshTimestamp;
private final Clock clock;
public ObjectCache(Supplier supplier, long cacheDuration, TimeUnit unit) {
this(supplier, cacheDuration, unit, Clock.systemUTC());
}
ObjectCache(Supplier supplier, long cacheDuration, TimeUnit unit, Clock clock) {
this.supplier = supplier;
this.cachedInstance = null;
this.cacheDurationMillis = unit.toMillis(cacheDuration);
this.clock = clock;
}
public synchronized T get() {
long now = clock.millis();
if (cachedInstance == null || (now - lastRefreshTimestamp) >= cacheDurationMillis) {
cachedInstance = supplier.get();
lastRefreshTimestamp = now;
}
return cachedInstance;
}
}