JarCasting
Eventstore Client
The official Event Store page can be found at https://eventstore.org/
This project uses the Java 8 client for the EventStore available at https://github.com/msemys/esjc
Our adapter implementation is generic and can be used for any kind of event. Trivial mapping between domain objects and json-serializable objects should be implemented, if the domain objects themselves can not be serialized and deserialized.
In order to consume all events from a stream, method EventListeners.subscribeStream() should be called. There is a variant EventListenerssubscribeStreamStartingAt(...) when the stream should be consumed starting from a particular event number. The client ensures to reconnect to the eventstore after being disconnected for any reason.
The known eventstores for the client are configured by setting application properties as in the following (YML) example:
eventstores:
- name: eventstore-team-a
host: eventstore.host.name
port: 1113
username: admin
password: changeit
Usage example
Common
Event
@Value.Immutable
@DataClass
public interface SomethingHappened extends Event {
EventStreamId EVENT_STREAM_ID = EventStreamId.of(EventStoreName.of("default"), EventStreamName.of("test"));
EventType EVENT_TYPE = EventType.of("something-happened");
EventVersion EVENT_VERSION = EventVersion.of(3);
EventSchemaRef EVENT_SCHEMA_REF = EventSchemaRef.of(URI.create("https://test.com/ref"));
static ImmutableSomethingHappened.Builder builder() {
return ImmutableSomethingHappened.builder();
}
String foo();
Integer bar();
@Override
default EventType eventType() {
return EVENT_TYPE;
}
}
Serializable Event
@Value.Immutable
@DataClass
@JsonSerialize(as = ImmutableSomethingHappenedData.class)
@JsonDeserialize(as = ImmutableSomethingHappenedData.class)
public interface SomethingHappenedData extends EventData {
static ImmutableSomethingHappenedData.Builder builder() {
return ImmutableSomethingHappenedData.builder();
}
String foo();
Integer bar();
}
For consuming events of a particular stream
@Component
@AllArgsConstructor
@Slf4j
public class SomethingHappenedEventConsumer implements EventConsumer<SomethingHappenedData> {
@Override
public EventStreamId eventStreamId() {
return SomethingHappened.EVENT_STREAM_ID;
}
@Override
public void onEvent(SomethingHappenedData data, EventMetadata metadata) {
val event = SomethingHappened.builder()
.eventId(metadata.eventId())
.timestamp(data.timestamp())
.foo(data.foo())
.bar(data.bar)
.build();
log.info("received event {} with metadata {}", event, metadata);
// code to consume event should be placed here
}
@Override
public Class<? extends SomethingHappenedData> getSerializableDataType() {
return SomethingHappenedData.class;
}
@Override
public EventType eventType() {
return SomethingHappened.EVENT_TYPE;
}
}
For writing events to a particular stream
@Component
class SomethingHappenedEventConfiguration implements EventConfiguration<SomethingHappened> {
public SomethingHappenedData map(SomethingHappened somethingHappened) {
return SomethingHappenedData.builder()
.timestamp(somethingHappened.timestamp())
.foo(somethingHappened.foo())
.bar(somethingHappened.bar())
.build();
}
@Override
public EventStreamId eventStreamId() {
return EVENT_STREAM_ID;
}
@Override
public EventType getType() {
return EVENT_TYPE;
}
@Override
public EventVersion eventVersion() {
return EVENT_VERSION;
}
@Override
public EventSchemaRef eventSchemaRef() {
return EVENT_SCHEMA_REF;
}
@Override
public Function1<SomethingHappened, Object> mapper() {
return this::map;
}
}
