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OccurrentOccurrent

In-memory event store

Plain Java · Modules: occurrent-eventstore-inmemory

What is it?

Section titled “What is it?”

A simple in-memory implementation of the EventStore interface.

When to use?

Section titled “When to use?”

Mainly for testing purposes or for integration tests that doesn’t require a durable event store.

Dependencies

Section titled “Dependencies”
<dependency>
    <groupId>org.occurrent</groupId>
    <artifactId>occurrent-eventstore-inmemory</artifactId>
    <version>0.34.0</version>
</dependency>

Getting Started

Section titled “Getting Started”

Once you’ve imported the dependencies you create a new instance of org.occurrent.eventstore.inmemory.InMemoryEventStore. For example:

InMemoryEventStore eventStore = new InMemoryEventStore();

This implementation also supports filtered stream reads via org.occurrent.eventstore.api.blocking.ReadEventStreamWithFilter. See Stream Filtering for when and how to use it.

By default this store refuses a query that filters on the event data payload. Call withDataFieldReader(...) to give it one, see Filtering on Payload Data.

Now you can start reading and writing events to the EventStore:

CloudEvent event = CloudEventBuilder.v1()
                    .withId("eventId")
                    .withSource(URI.create("urn:mydomain"))
                    .withType("HelloWorld")
                    .withTime(LocalDateTime.now().atOffset(ZoneOffset.UTC))
                    .withSubject("subject")
                    .withDataContentType("application/json")
                    .withData("{ \"message\" : \"hello\" }".getBytes(StandardCharsets.UTF_8))
                    .build();


// Write
eventStore.write("streamId", List.of(event));


// Read
EventStream<CloudEvent> eventStream = eventStore.read("streamId");


// Read filtered events when the store supports it
if (eventStore instanceof ReadEventStreamWithFilter filteredEventStore) {
    EventStream<CloudEvent> filteredEventStream = filteredEventStore.read(
            "streamId",
            StreamReadFilter.type("com.example.NameDefined")
    );
}