FilteringEventStorageEngine (Axon Framework 4.4 API)

java.lang.Object
- org.axonframework.eventsourcing.FilteringEventStorageEngine

All Implemented Interfaces:

EventStorageEngine
```
public class FilteringEventStorageEngine
extends Object
implements EventStorageEngine
```
Implementation of EventStorageEngine that delegates to another implementation, while filtering events as they are appended. This prevents certain events to be stored in the Event Store.

Since:

3.1

Author:

Allard Buijze

Constructor Summary

Constructors
Constructor and Description
`FilteringEventStorageEngine(EventStorageEngine delegate, Predicate<? super EventMessage<?>> filter)` Initializes the FilteringEventStorageEngine delegating all event messages matching the given `filter` to the given `delegate`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`appendEvents(EventMessage<?>... events)` Append one or more events to the event storage.
`void`	`appendEvents(List<? extends EventMessage<?>> events)` Append a list of events to the event storage.
`TrackingToken`	`createHeadToken()` Creates a token that is at the head of an event stream - that tracks all new events.
`TrackingToken`	`createTailToken()` Creates a token that is at the tail of an event stream - that tracks events from the beginning of time.
`TrackingToken`	`createTokenAt(Instant dateTime)` Creates a token that tracks all events after given `dateTime`.
`Optional<Long>`	`lastSequenceNumberFor(String aggregateIdentifier)` Returns the last known sequence number for the given `aggregateIdentifier`.
`DomainEventStream`	`readEvents(String aggregateIdentifier)` Get a `DomainEventStream` containing all events published by the aggregate with given `aggregateIdentifier`.
`DomainEventStream`	`readEvents(String aggregateIdentifier, long firstSequenceNumber)` Get a `DomainEventStream` containing all events published by the aggregate with given `aggregateIdentifier` starting with the first event having a sequence number that is equal or larger than the given `firstSequenceNumber`.
`Stream<? extends TrackedEventMessage<?>>`	`readEvents(TrackingToken trackingToken, boolean mayBlock)` Open an event stream containing all events stored since given tracking token.
`Optional<DomainEventMessage<?>>`	`readSnapshot(String aggregateIdentifier)` Try to load a snapshot event of the aggregate with given `aggregateIdentifier`.
`void`	`storeSnapshot(DomainEventMessage<?> snapshot)` Store an event that contains a snapshot of an aggregate.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - FilteringEventStorageEngine
```
public FilteringEventStorageEngine(EventStorageEngine delegate,
                                   Predicate<? super EventMessage<?>> filter)
```
    Initializes the FilteringEventStorageEngine delegating all event messages matching the given filter to the given delegate.
    Note that this only affects events stored in the StorageEngine. The EventStore will still publish these events to Subscribed event handlers. Tracking Event Processors take their events from the stored events, and will therefore not receive any events blocked by this instance.
    
    Parameters:
    
    delegate - the EventStorageEngine to store matching messages in
    
    filter - the predicate that event messages must match against to be stored
- Method Detail
  - appendEvents
```
public void appendEvents(EventMessage<?>... events)
```
    Description copied from interface: EventStorageEngine
    
    Append one or more events to the event storage. Events will be appended in the order that they are offered in.
    Note that all events should have a unique event identifier. When storing domain events events should also have a unique combination of aggregate id and sequence number.
    By default this method creates a list of the offered events and then invokes EventStorageEngine.appendEvents(List).
    
    Specified by:
    
    appendEvents in interface EventStorageEngine
    
    Parameters:
    
    events - Events to append to the event storage
  - appendEvents
```
public void appendEvents(List<? extends EventMessage<?>> events)
```
    Description copied from interface: EventStorageEngine
    
    Append a list of events to the event storage. Events will be appended in the order that they are offered in.
    Note that all events should have a unique event identifier. When storing domain events events should also have a unique combination of aggregate id and sequence number.
    
    Specified by:
    
    appendEvents in interface EventStorageEngine
    
    Parameters:
    
    events - Events to append to the event storage
  - storeSnapshot
```
public void storeSnapshot(DomainEventMessage<?> snapshot)
```
    Description copied from interface: EventStorageEngine
    
    Store an event that contains a snapshot of an aggregate. If the event storage already contains a snapshot for the same aggregate, then it will be replaced with the given snapshot.
    
    Specified by:
    
    storeSnapshot in interface EventStorageEngine
    
    Parameters:
    
    snapshot - The snapshot event of the aggregate that is to be stored
  - readEvents
```
public Stream<? extends TrackedEventMessage<?>> readEvents(TrackingToken trackingToken,
                                                           boolean mayBlock)
```
    Description copied from interface: EventStorageEngine
    
    Open an event stream containing all events stored since given tracking token. The returned stream is comprised of events from aggregates as well as other application events. Pass a trackingToken of null to open a stream containing all available events.
    If the value of the given mayBlock is true the returned stream is allowed to block while waiting for new event messages if the end of the stream is reached.
    
    Specified by:
    
    readEvents in interface EventStorageEngine
    
    Parameters:
    
    trackingToken - Object describing the global index of the last processed event or null to create a stream of all events in the store
    
    mayBlock - If true the storage engine may optionally choose to block to wait for new event messages if the end of the stream is reached.
    
    Returns:
    
    A stream containing all tracked event messages stored since the given tracking token
  - readEvents
```
public DomainEventStream readEvents(String aggregateIdentifier)
```
    Description copied from interface: EventStorageEngine
    
    Get a DomainEventStream containing all events published by the aggregate with given aggregateIdentifier. By default calling this method is shorthand for an invocation of EventStorageEngine.readEvents(String, long) with a sequence number of 0.
    The returned stream is finite, i.e. it should not block to wait for further events if the end of the event stream of the aggregate is reached.
    
    Specified by:
    
    readEvents in interface EventStorageEngine
    
    Parameters:
    
    aggregateIdentifier - The identifier of the aggregate to return an event stream for
    
    Returns:
    
    A non-blocking DomainEventStream of the given aggregate
  - readEvents
```
public DomainEventStream readEvents(String aggregateIdentifier,
                                    long firstSequenceNumber)
```
    Description copied from interface: EventStorageEngine
    
    Get a DomainEventStream containing all events published by the aggregate with given aggregateIdentifier starting with the first event having a sequence number that is equal or larger than the given firstSequenceNumber.
    The returned stream is finite, i.e. it should not block to wait for further events if the end of the event stream of the aggregate is reached.
    
    Specified by:
    
    readEvents in interface EventStorageEngine
    
    Parameters:
    
    aggregateIdentifier - The identifier of the aggregate
    
    firstSequenceNumber - The expected sequence number of the first event in the returned stream
    
    Returns:
    
    A non-blocking DomainEventStream of the given aggregate
  - readSnapshot
```
public Optional<DomainEventMessage<?>> readSnapshot(String aggregateIdentifier)
```
    Description copied from interface: EventStorageEngine
    
    Try to load a snapshot event of the aggregate with given aggregateIdentifier. If the storage engine has no snapshot event of the aggregate, an empty Optional is returned.
    
    Specified by:
    
    readSnapshot in interface EventStorageEngine
    
    Parameters:
    
    aggregateIdentifier - The identifier of the aggregate
    
    Returns:
    
    An optional with a snapshot of the aggregate
  - lastSequenceNumberFor
```
public Optional<Long> lastSequenceNumberFor(String aggregateIdentifier)
```
    Description copied from interface: EventStorageEngine
    
    Returns the last known sequence number for the given aggregateIdentifier.
    While it's recommended to use the sequence numbers from the DomainEventStream, there are cases where knowing the sequence number is required, without having read the actual events. In such case, this method is a viable alternative.
    
    Specified by:
    
    lastSequenceNumberFor in interface EventStorageEngine
    
    Parameters:
    
    aggregateIdentifier - The identifier to find the last sequence number for
    
    Returns:
    
    an optional with the highest sequence number, or an empty optional if the aggregate identifier wasn't found
  - createTailToken
```
public TrackingToken createTailToken()
```
    Description copied from interface: EventStorageEngine
    
    Creates a token that is at the tail of an event stream - that tracks events from the beginning of time.
    
    Specified by:
    
    createTailToken in interface EventStorageEngine
    
    Returns:
    
    a tracking token at the tail of an event stream, if event stream is empty null is returned
  - createHeadToken
```
public TrackingToken createHeadToken()
```
    Description copied from interface: EventStorageEngine
    
    Creates a token that is at the head of an event stream - that tracks all new events.
    
    Specified by:
    
    createHeadToken in interface EventStorageEngine
    
    Returns:
    
    a tracking token at the head of an event stream, if event stream is empty null is returned
  - createTokenAt
```
public TrackingToken createTokenAt(Instant dateTime)
```
    Description copied from interface: EventStorageEngine
    
    Creates a token that tracks all events after given dateTime. If there is an event exactly at the given dateTime, it will be tracked too.
    
    Specified by:
    
    createTokenAt in interface EventStorageEngine
    
    Parameters:
    
    dateTime - The date and time for determining criteria how the tracking token should be created. A tracking token should point to very first event before this date and time.
    
    Returns:
    
    a tracking token at the given dateTime, if there aren't events matching this criteria null is returned

Class FilteringEventStorageEngine

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

FilteringEventStorageEngine

Method Detail

appendEvents

appendEvents

storeSnapshot

readEvents

readEvents

readEvents

readSnapshot

lastSequenceNumberFor

createTailToken

createHeadToken

createTokenAt