How to get evicted value from org.apache.cayenne.util.concurrentlinkedhashmap?

Question

I am using org.apache.cayenne.util.concurrentlinkedhashmap and setting cache capacity by using maximumWeightedCpacity(3000) method once cache reached to its threshold limit it starts evicting the old entries. I need that entries which is getting evicted. How Can I get those entries using listener?

Answer 1

That is an embedded copy of the ConcurrentLinkedHashMap library. The tutorial provides an example using an EvictionListener and can be written as,

ConcurrentMap<K, V> cache = new ConcurrentLinkedHashMap.Builder<K, V>()
    .maximumWeightedCapacity(3_000)
    .listener((key, value) ->
        System.out.printf("Evicted key=%s, value=%s%n", key, value))
    .build();

While this library is small and nibble, it was written in the Java 5 timeframe. It is still excellent for embedded cases to minimize the jar size, but general purpose usages should prefer Caffeine instead. That library provides a richer feature set and additional performance improvements.

Cache<K, V> graphs = Caffeine.newBuilder()
    .maximumSize(3_000)
    .removalListener((K key, V value, RemovalCause cause) ->
        System.out.printf("%s: key=%s, value=%s%n", cause, key, value))
    .build();