org.springframework.boot.context.properties.source.SoftReferenceConfigurationPropertyCache Maven / Gradle / Ivy
/*
* Copyright 2012-2020 the original author or authors.
*
* 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
*
* https://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.springframework.boot.context.properties.source;
import java.lang.ref.SoftReference;
import java.time.Duration;
import java.time.Instant;
import java.util.function.Supplier;
import java.util.function.UnaryOperator;
/**
* Simple cache that uses a {@link SoftReference} to cache a value for as long as
* possible.
*
* @param the value type
* @author Phillip Webb
*/
class SoftReferenceConfigurationPropertyCache implements ConfigurationPropertyCaching {
private static final Duration UNLIMITED = Duration.ZERO;
private final boolean neverExpire;
private volatile Duration timeToLive;
private volatile SoftReference value = new SoftReference<>(null);
private volatile Instant lastAccessed = now();
SoftReferenceConfigurationPropertyCache(boolean neverExpire) {
this.neverExpire = neverExpire;
}
@Override
public void enable() {
this.timeToLive = UNLIMITED;
}
@Override
public void disable() {
this.timeToLive = null;
}
@Override
public void setTimeToLive(Duration timeToLive) {
this.timeToLive = (timeToLive == null || timeToLive.isZero()) ? null : timeToLive;
}
@Override
public void clear() {
this.lastAccessed = null;
}
/**
* Get an value from the cache, creating it if necessary.
* @param factory a factory used to create the item if there is no reference to it.
* @param refreshAction action called to refresh the value if it has expired
* @return the value from the cache
*/
T get(Supplier factory, UnaryOperator refreshAction) {
T value = getValue();
if (value == null) {
value = refreshAction.apply(factory.get());
setValue(value);
}
else if (hasExpired()) {
value = refreshAction.apply(value);
setValue(value);
}
if (!this.neverExpire) {
this.lastAccessed = now();
}
return value;
}
private boolean hasExpired() {
if (this.neverExpire) {
return false;
}
Duration timeToLive = this.timeToLive;
Instant lastAccessed = this.lastAccessed;
if (timeToLive == null || lastAccessed == null) {
return true;
}
return !UNLIMITED.equals(timeToLive) && now().isAfter(lastAccessed.plus(timeToLive));
}
protected Instant now() {
return Instant.now();
}
protected T getValue() {
return this.value.get();
}
protected void setValue(T value) {
this.value = new SoftReference<>(value);
}
}