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/*
* Copyright (c) 2020. AxonIQ
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.axoniq.axonserver.connector.event;
import io.axoniq.axonserver.connector.impl.StreamClosedException;
import io.axoniq.axonserver.grpc.event.Event;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* A stream of Events for a single Aggregate. The operations on this stream are blocking and intended for Event Sourcing
* purposes, where an Aggregate's state needs to be reconstructed based on historic events.
*/
public interface AggregateEventStream {
/**
* Returns the next available event, possibly blocking until one becomes available for reading.
*
* @return the next event
* @throws InterruptedException if the current thread was interrupted while waiting for an event to become
* available
* @throws StreamClosedException when the stream has reached the end or was closed for another reason
* @see #hasNext() to verify availability of events
*/
Event next() throws InterruptedException;
/**
* Indicates whether a new event is available. This method may block while waiting for a confirmation if an event is
* available for reading.
*
* @return {@code true} if a message is available, or {@code false} if the stream has reached the end
* @throws StreamClosedException if the stream has been closed prematurely because of an error or on client request
*/
boolean hasNext();
/**
* Close this stream for further reading, notifying the provider of Events to stop streaming them. Any event already
* emitted by the sender may still be consumed.
*
* Note that after calling {@code cancel}, {@link #hasNext()} may throw a {@link StreamClosedException} if the
* cancellation caused the stream to close before the last message was received.
*/
void cancel();
/**
* Returns a Stream that consumes the Events from this instance. Note that this instance should not be read from in
* parallel to the returned stream, as this may provide undefined results on the availability of events in either
* stream instance.
*
* @return a Stream containing the Events contained in this stream
*/
default Stream asStream() {
return StreamSupport.stream(new Spliterator() {
@Override
public boolean tryAdvance(Consumer action) {
if (hasNext()) {
try {
action.accept(next());
return true;
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return false;
}
}
return false;
}
@Override
public Spliterator trySplit() {
return null;
}
@Override
public long estimateSize() {
return Integer.MAX_VALUE;
}
@Override
public int characteristics() {
return Spliterator.NONNULL & Spliterator.ORDERED & Spliterator.IMMUTABLE & Spliterator.DISTINCT;
}
}, false);
}
}