org.apache.juneau.internal.Cache Maven / Gradle / Ivy
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// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance *
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// * *
// * http://www.apache.org/licenses/LICENSE-2.0 *
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package org.apache.juneau.internal;
import java.util.concurrent.*;
/**
* Simple in-memory cache of objects.
*
*
* Essentially just a wrapper around a ConcurrentHashMap.
*
* @param The key type.
* @param The value type.
*/
public class Cache {
private final boolean nocache;
private final int maxSize;
private final ConcurrentHashMap cache;
/**
* Constructor.
*
* @param disabled If true then the cache is disabled.
* @param maxSize The maximum size of the cache. If this threshold is reached, the cache is flushed.
*/
public Cache(boolean disabled, int maxSize) {
this.nocache = disabled;
this.maxSize = maxSize;
if (! nocache)
cache = new ConcurrentHashMap<>();
else
cache = null;
}
/**
* Retrieves the value with the specified key from this cache.
*
* @param key The key.
* @return The value, or null if the value is not in the cache, or the cache is disabled.
*/
public V get(K key) {
if (nocache)
return null;
return cache.get(key);
}
/**
* Adds the value with the specified key to this cache.
*
* @param key The key.
* @param value The value.
* @return
* Either the value already in the cache if it already exists, or the same value passed in.
* Always returns the same value if the cache is disabled.
*/
public V put(K key, V value) {
if (nocache)
return value;
// Prevent OOM in case of DDOS
if (cache.size() > maxSize)
cache.clear();
while (true) {
V v = cache.get(key);
if (v != null)
return v;
cache.putIfAbsent(key, value);
return value;
}
}
}