org.infinispan.container.MergeOnStore Maven / Gradle / Ivy
package org.infinispan.container;
/**
* This interface is not a public API.
*
* A value implementing this interface is merged with the actual value when storing
* into {@link org.infinispan.container.DataContainer}.
* As the merge operation is synchronized externally, the implementation of this interface does not need to be
* thread-safe. Note that the value in context (last written value) needs to implement {@link MergeOnStore},
* if the cache already containing such instance is overwritten by a non-implementor, the merge does not happen.
*
*
The intended use is when executing a command with {@link org.infinispan.context.Flag#SKIP_LOCKING}; in that case
* we may have two different instances in context at one moment and the writes may be applied in any order, even
* in a different order on different owners. Therefore it's strongly recommended that all operations on such entry
* are commutative (order-independent).
*
*
As the atomicity of load & store into persistence layer cannot be guaranteed, it is recommended to use such values
* only with {@link org.infinispan.context.Flag#SKIP_CACHE_LOAD} and
* {@link org.infinispan.context.Flag#SKIP_CACHE_STORE} or implementing a custom externalizer that will deal with this.
*/
public interface MergeOnStore {
/**
* @param other Actual value stored in the cache, or null if the entry does not exist.
* @return Value that will be stored in the cache, or null if it should be removed.
*/
Object merge(Object other);
}