Package org.axonframework.messaging.eventstreaming

Interface TrackingTokenSource

All Known Subinterfaces:

EventStore, StreamableEventSource

All Known Implementing Classes:

InterceptingEventStore, RecordingEventStore, StorageEngineBackedEventStore

public interface TrackingTokenSource

Provides functionality to retrieve TrackingTokens for the head and tail of the stream, and at a given point in time in the stream.

Since:

5.0.0

Author:

Allard Buijze, Mateusz Nowak, Rene de Waele, Steven van Beelen

Method Summary

Modifier and Type	Method	Description
CompletableFuture<TrackingToken>	firstToken(ProcessingContext context)	Creates a TrackingToken representing the first position of the event stream.
CompletableFuture<TrackingToken>	latestToken(ProcessingContext context)	Creates a TrackingToken representing the latest position, thus pointing at the next event of the event stream.
CompletableFuture<TrackingToken>	tokenAt(Instant at, ProcessingContext context)	Creates a TrackingToken tracking all events after the given at from an event stream.

Method Details

firstToken

CompletableFuture<TrackingToken> firstToken(@Nullable
 ProcessingContext context)

Creates a TrackingToken representing the first position of the event stream.

As the retrieved token represents the point from which to

invalid reference

open

the event stream, the first event to be streamed when opening is the one right after the returned token.

Subsequent invocation of this method will yield the same result, unless the stream's initial values are deleted.

Parameters:

context - The current ProcessingContext, if any.

Returns:

A CompletableFuture of a TrackingToken representing the first event of the event stream.

latestToken

CompletableFuture<TrackingToken> latestToken(@Nullable
 ProcessingContext context)

Creates a TrackingToken representing the latest position, thus pointing at the next event of the event stream.

As the retrieved token represents the point from which to

invalid reference

open

the event stream, the first event to be streamed when opening is the one right after the returned token.

Since the event stream of this source is theoretically infinite, subsequent invocation of this operation typically return a different token. Only if this StreamableEventSource is idle, will several latestToken() invocations result in the same TrackingToken.

Parameters:

context - The current ProcessingContext, if any.

Returns:

A CompletableFuture of a TrackingToken representing the latest event, thus pointing at the next event of the event stream.

tokenAt

CompletableFuture<TrackingToken> tokenAt(@Nonnull
 Instant at,
 @Nullable
 ProcessingContext context)

Creates a TrackingToken tracking all events after the given at from an event stream.

When there is an EventMessage exactly at the given dateTime, it will be tracked too.

Parameters:

at - The Instant determining how the TrackingToken should be created. The returned token points at very first event before this Instant.

context - The current ProcessingContext, if any.

Returns:

A CompletableFuture of TrackingToken pointing at the very first event before the given at of the event stream.