Package org.trellisldp.api

Interface MementoService

All Known Implementing Classes:

DBWrappedMementoService, FileMementoService, NoopMementoService

public interface MementoService

An interface for a Memento subsystem. Mementos of Resources may be made and retrieved using this service. Mementos may also be recorded by other means, including by the persistence layer independently of Trellis, but unless they are retrieved via this service, Trellis will not publish them as HTTP resources. Mementos of NonRDFSources (like any other Resource) may also be made and retrieved here, but the associated InputStreams are made (like all binary InputStreams) via a BinaryService implementation.

Method Summary

Modifier and Type	Method	Description
CompletionStage<Resource>	get(IRI identifier, Instant time)	Fetch a Memento resource for the given time.
CompletionStage<SortedSet<Instant>>	mementos(IRI identifier)	Get the times for all of the Mementos of the given resource.
CompletionStage<Void>	put(Resource resource)	Create a new Memento for a resource.
default CompletionStage<Void>	put(ResourceService resourceService, IRI identifier)	Create a new Memento for a resource, retrieved from a ResourceService.

Method Detail

put

default CompletionStage<Void> put(ResourceService resourceService,
                                  IRI identifier)

Create a new Memento for a resource, retrieved from a ResourceService.

Parameters:

resourceService - the resource service.

identifier - the identifier.

Returns:

a new completion stage that, when the stage completes normally, indicates that the Memento resource was successfully created in the corresponding persistence layer.

Implementation Requirements:

The default implementation of this method fetches a resource from a ResourceService that is external to the Memento service., An implementation may choose to store a new Memento only when this method is called, or at other times as well, e.g. when ResourceService.replace(org.trellisldp.api.Metadata, org.apache.commons.rdf.api.Dataset) is called.

Implementation Note:

In the case that the two services are managed by the same persistence layer, it may not be necessary to fetch a Resource from the persistence layer, in which case this method can be overridden as a no-op method, e.g. return completedFuture(null);.

put

CompletionStage<Void> put(Resource resource)

Create a new Memento for a resource.

Parameters:

resource - the resource

Returns:

a new completion stage that, when the stage completes normally, indicates that the Memento resource was successfully created in the corresponding persistence layer. In the case of an unsuccessful write operation, the CompletionStage will complete exceptionally and can be handled with CompletionStage.handle(java.util.function.BiFunction<? super T, java.lang.Throwable, ? extends U>), CompletionStage.exceptionally(java.util.function.Function<java.lang.Throwable, ? extends T>) or similar methods.

get

CompletionStage<Resource> get(IRI identifier,
                              Instant time)

Fetch a Memento resource for the given time.

Parameters:

identifier - the resource identifier

time - the requested time

Returns:

the new completion stage, containing the fetched resource

mementos

CompletionStage<SortedSet<Instant>> mementos(IRI identifier)

Get the times for all of the Mementos of the given resource.

Parameters:

identifier - the resource identifier

Returns:

the new completion stage containing a collection of Memento dateTimes