README.md

Event Store Kafka

CDI extension for Java EE 8 application using Apache Kafka as Event Store.

Five minute start

How to quickly start using the Event Store Kafka with your Java EE 8 project.

Setup

1. Add maven dependencies to your pom.xml

   <dependency>
       <groupId>net.osomahe</groupId>
       <artifactId>eventstore-kafka</artifactId>
       <version>0.4.3</version>
   </dependency>

2. Added extensions src/main/resources/META-INF/services/javax.enterprise.inject.spi.Extension

   net.osomahe.esk.EventStoreExtension
   

Producing events

1. Extend AbstractEvent class
2. Use EventStorePublisher#publish(event) method for publishing event to Apache Kafka synchronously. or
3. Use EventStorePublisher#publishAsync(event) method for publishing event to Apache Kafka asynchronously.

Consuming events

1. Extend AbstractEvent class or use the same as for publishing.
2. Observes for CDI event

   public void handleCreate(@Observes TodoCreatedEvent event) {
       // do some magic with event
   }

Advanced

Configuration possibilities and default values. Unfortunately JavaEE 8 does not have any standard means of configuration and I didn't want to

Configuration

Unfortunately JavaEE 8 does not provide any standard way. There are two ways of configuring the eventstore-kafka.

1. Application has to produce using @Produces and correct qualifier see example:

• java.util.Properties with qualifiers @KafkaProducerConfig for overriding producer properties otherwise default values will be in place.

  Properties props = new Properties();
  props.put(BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
  props.put(ACKS_CONFIG, "all");

• java.util.Properties with qualifiers @KafkaConsumerConfig for overriding consumer properties otherwise default values will be in place.

  Properties props = new Properties();
  props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
  props.put(GROUP_ID_CONFIG, "client-application");
  props.put(AUTO_OFFSET_RESET_CONFIG, "earliest");

2. Application has to implement EventStorePublisherConfig and (or) EventStoreConsumerConfig to provide non-default properties

Customization

• @TopicName annotation for an event class to set different topic for given event(s)
• @EventName annotation for an event class to set different event name
• @AsyncEvent annotation for an event class to set asynchronous processing of events @ObeservesAsync required for handling async events