Package org.axonframework.eventsourcing.eventstore

Class DefaultEventStoreTransaction

java.lang.Object

org.axonframework.eventsourcing.eventstore.DefaultEventStoreTransaction

All Implemented Interfaces:

EventStoreTransaction

public class DefaultEventStoreTransaction
extends Object
implements EventStoreTransaction

The default EventStoreTransaction.

While sourcing it will map the SourcingCondition into an AppendCondition for appending, taking into account several sourcing invocation might have occurred in the same ProcessingContext. Every event that is appended is collected, and the collection is handed to the EventStorageEngine as a single batch during the

invalid reference

Phases#APPEND_EVENTS

phase of the ProcessingContext. That phase follows prepare-commit, so a component invoked during prepare-commit can still append. Appending after it has run is rejected.

Since:

5.0.0

Author:

Steven van Beelen, John Hendrikx

Field Summary

Fields inherited from interface org.axonframework.eventsourcing.eventstore.EventStoreTransaction

APPEND_EVENTS

Constructor Summary

Constructors

Constructor	Description
DefaultEventStoreTransaction(EventStorageEngine eventStorageEngine, ProcessingContext processingContext, Function<EventMessage,TaggedEventMessage<?>> eventTagger)	Constructs a DefaultEventStoreTransaction using the given eventStorageEngine to append events originating from the given context.

Method Summary

Modifier and Type	Method	Description
void	appendEvent(EventMessage eventMessage)	Appends an eventMessage to be appended to an EventStore in this transaction.
ConsistencyMarker	appendPosition()	Returns the position in the event store of the last appended event by this transaction.
void	onAppend(Consumer<EventMessage> callback)	Registers a callback to invoke when an event is appended to this transaction.
void	overrideAppendCondition(UnaryOperator<AppendCondition> conditionOverride)	Overrides the AppendCondition that will be used when committing this transaction.
MessageStream<? extends EventMessage>	source(SourcingCondition condition)	Sources a MessageStream of type EventMessage based on the given condition that can be used to rehydrate a model.
MessageStream<? extends EventMessage>	source(SourcingCondition condition, @Nullable Consumer<Position> resumePositionCallback)	Sources a MessageStream of type EventMessage based on the given condition, optionally invoking the given resume position callback.

Methods inherited from class java.lang.Object

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

Constructor Details

DefaultEventStoreTransaction

public DefaultEventStoreTransaction(EventStorageEngine eventStorageEngine,
 ProcessingContext processingContext,
 Function<EventMessage,TaggedEventMessage<?>> eventTagger)

Constructs a DefaultEventStoreTransaction using the given eventStorageEngine to append events originating from the given context.

Parameters:

eventStorageEngine - The EventStorageEngine used to append events with.

processingContext - The ProcessingContext from which to append events and attach resources to.

eventTagger - A function that will process each EventMessage to attach Tags, before it is added to the transaction.

Method Details

source

public MessageStream<? extends EventMessage> source(SourcingCondition condition)

Description copied from interface: EventStoreTransaction

Sources a MessageStream of type EventMessage based on the given condition that can be used to rehydrate a model.

Note that using no criteria does not make sense for sourcing, as it is not recommended to source the entire event store.

Any EventStoreTransaction using the EventStorageEngine.source(SourcingCondition) is expected to filter the TerminalEventMessage with the ConsistencyMarker.

Specified by:

source in interface EventStoreTransaction

Parameters:

condition - The SourcingCondition used to retrieve the MessageStream containing the sequence of events that can rehydrate a model.

Returns:

The MessageStream of type EventMessage containing the event sequence complying to the given condition.

source

public MessageStream<? extends EventMessage> source(SourcingCondition condition,
 @Nullable Consumer<Position> resumePositionCallback)

Description copied from interface: EventStoreTransaction

Sources a MessageStream of type EventMessage based on the given condition, optionally invoking the given resume position callback.

The provided resumePositionCallback, if non-null, is invoked at most once and only after the returned MessageStream has been consumed completely. For most implementations, the resume position is only known when the stream reaches its terminal event. As such, the callback is guaranteed to be invoked only if the stream is fully consumed.

If sourcing completes and no events are found, the callback will be invoked with the position specified in sourcingCondition or with a greater position. Returning a greater position allows resuming from a point that already excludes positions known to be non-matching.

If the stream terminates with an error, is closed prematurely, or is not consumed to completion, the callback is not guaranteed to be invoked.

The callback should not throw exceptions; doing so may result in undefined behavior.

Note that using no criteria does not make sense for sourcing, as it is not recommended to source the entire event store.

Any EventStoreTransaction using the EventStorageEngine.source(SourcingCondition) is expected to filter the TerminalEventMessage with the ConsistencyMarker.

Specified by:

source in interface EventStoreTransaction

Parameters:

condition - The SourcingCondition used to retrieve the MessageStream containing the sequence of events that can rehydrate a model.

resumePositionCallback - An optional callback that receives the Position from which sourcing may be resumed once it becomes available; the position provided is never null.

Returns:

The MessageStream of type EventMessage containing the event sequence complying to the given condition.

appendEvent

public void appendEvent(EventMessage eventMessage)

Description copied from interface: EventStoreTransaction

Appends an eventMessage to be appended to an EventStore in this transaction.

Specified by:

appendEvent in interface EventStoreTransaction

Parameters:

eventMessage - The EventMessage to append.

overrideAppendCondition

public void overrideAppendCondition(UnaryOperator<AppendCondition> conditionOverride)

Description copied from interface: EventStoreTransaction

Overrides the AppendCondition that will be used when committing this transaction. The provided conditionOverride function receives the current AppendCondition derived from sourcing calls (or AppendCondition.none() if no sourcing occurred) and returns the desired condition.

This allows two primary use cases:

1. Appending without sourcing — enforcing uniqueness constraints without first sourcing events. The input is AppendCondition.none(), and the override sets the desired criteria and marker (e.g., AppendCondition.withCriteria(EventCriteria) which uses ConsistencyMarker.ORIGIN to check against the entire event store).
2. Narrowing (or broadening) the append condition — sourcing events with broad criteria for state but only a subset causes real conflicts. The override can narrow the criteria via AppendCondition.replaceCriteria(EventCriteria) while preserving the sourced marker.

Multiple calls to this method compose: each subsequent override receives the output of the previous one. The override is applied at commit time, after all source calls have been processed.

Returning AppendCondition.none() (or null) from the override function bypasses conflict detection entirely.

Specified by:

overrideAppendCondition in interface EventStoreTransaction

Parameters:

conditionOverride - a UnaryOperator that transforms the current AppendCondition

onAppend

public void onAppend(Consumer<EventMessage> callback)

Description copied from interface: EventStoreTransaction

Registers a callback to invoke when an event is appended to this transaction.

Each callback registration adds a new callback that is invoked on the appendEvent(EventMessage, AppendCondition) operation.

Specified by:

onAppend in interface EventStoreTransaction

Parameters:

callback - A Consumer to invoke when an event is appended in this transaction.

appendPosition

public ConsistencyMarker appendPosition()

Description copied from interface: EventStoreTransaction

Returns the position in the event store of the last appended event by this transaction.

Will return ConsistencyMarker.ORIGIN if nothing has been appended yet.

Specified by:

appendPosition in interface EventStoreTransaction

Returns:

The position in the event store of the last appended event by this transaction.