Class PutIfAbsentMergePolicy<K,V>

java.lang.Object

com.loomcache.server.wan.merge.PutIfAbsentMergePolicy<K,V>

Type Parameters:

K - key type

V - value type

All Implemented Interfaces:

MergePolicy<K,V>

public final class PutIfAbsentMergePolicy<K,V>
extends Object
implements MergePolicy<K,V>

Insert-only merge policy.

Accepts the incoming value only if no existing local value is present. Existing values are never overwritten by incoming WAN events under this policy — useful for immutable caches (e.g., content-addressable storage, precomputed results) where overwrites indicate a bug.

Since:

2.0

Nested Class Summary

Nested classes/interfaces inherited from interface MergePolicy

MergePolicy.MergeEntry<V>

Field Summary

Fields inherited from interface MergePolicy

NO_EXPIRATION_TIME_MILLIS

Constructor Summary

Constructors

Constructor	Description
PutIfAbsentMergePolicy()

Method Summary

Modifier and Type	Method	Description
static <K,V> @NonNull PutIfAbsentMergePolicy<K,V>	instance()	Return the shared instance of this stateless policy.
@NonNull Optional<V>	merge(@NonNull K key, @NonNull MergePolicy.MergeEntry<V> incoming, @Nullable MergePolicy.MergeEntry<V> existing)	Merge an incoming replication entry against the existing local entry.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

PutIfAbsentMergePolicy

public PutIfAbsentMergePolicy()

Method Details

instance

public static <K,V>
@NonNull PutIfAbsentMergePolicy<K,V> instance()

Return the shared instance of this stateless policy.

Type Parameters:

K - key type

V - value type

Returns:

a shared PutIfAbsentMergePolicy instance

merge

public @NonNull Optional<V> merge(@NonNull K key,
 @NonNull MergePolicy.MergeEntry<V> incoming,
 @Nullable MergePolicy.MergeEntry<V> existing)

Description copied from interface: MergePolicy

Merge an incoming replication entry against the existing local entry.

Specified by:

merge in interface MergePolicy<K,V>

Parameters:

key - the key being replicated (non-null)

incoming - the incoming entry from the remote cluster (non-null)

existing - the current local entry, or null if the key has no local value

Returns:

the value to keep (non-empty to apply, empty to reject the incoming)