Package com.opencqrs.framework.command.cache

Interface StateRebuildingCache

All Known Implementing Classes:

LruInMemoryStateRebuildingCache, NoStateRebuildingCache

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface StateRebuildingCache

Interface specifying operations to cache event-sourced instance state to reduce the number of fetched events prior to executing a CommandHandler.

See Also:

• fetchAndMerge(CacheKey, Function)

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static final record	StateRebuildingCache.CacheKey<I>	Represents the cache key, whose equality determines, which StateRebuildingCache.CacheValue to fetch.
static final record	StateRebuildingCache.CacheValue<I>	Represents the cache value.

Method Summary

Modifier and Type	Method	Description
<I> StateRebuildingCache.CacheValue<I>	fetchAndMerge(StateRebuildingCache.CacheKey<I> key, Function<StateRebuildingCache.CacheValue<I>,StateRebuildingCache.CacheValue<I>> mergeFunction)	Method supposed to fetch a StateRebuildingCache.CacheValue from the underlying cache based on the given StateRebuildingCache.CacheKey.

Method Details

fetchAndMerge

<I> StateRebuildingCache.CacheValue<I> fetchAndMerge(StateRebuildingCache.CacheKey<I> key,
 Function<StateRebuildingCache.CacheValue<I>,StateRebuildingCache.CacheValue<I>> mergeFunction)

Method supposed to fetch a StateRebuildingCache.CacheValue from the underlying cache based on the given StateRebuildingCache.CacheKey. The cached value is applied to the given mergeFunction, the underlying cache updated with the merged StateRebuildingCache.CacheValue, before it is returned to the caller. Implementations may choose to return an even newer StateRebuildingCache.CacheValue, if concurrent merges occur.

Type Parameters:

I - the generic instance type being cached

Parameters:

key - the cache key

mergeFunction - a merge function updating a StateRebuildingCache.CacheValue previously cached, typically by fetching newer events, applying them to the instance and returning the merged value, which will then be applied to the underlying cache (if no newer value has already been applied concurrently, depending on the concurrency guarantees of the implementation). In case of a cache miss, a StateRebuildingCache.CacheValue with null contents will be passed to the merge function, as annotated.

Returns:

the fetched and merged cache value