org.zalando.nakadiproducer.eventlog

Interface EventLogWriter

All Known Implementing Classes:

EventLogWriterImpl

public interface EventLogWriter

The main user interface for this library. Autowire an instance of this interface into your service, and call one of the methods whenever you want to send an event.

All the methods are supposed to be called inside the same database transaction which also contains the corresponding changes to your business objects. This way it is made sure that the events are persisted if and only if the containing transaction is successful, sidestepping the distributed transaction problem.

The library will later try to submit all those persisted events to Nakadi.

Method Summary

Modifier and Type	Method and Description
void	fireBusinessEvent(String eventType, Object payload) Fires a business event, i.e. an event communicating the fact that some business process step happened.
void	fireCreateEvent(String eventType, String dataType, Object data) Fires a data change event about a creation of some resource (object).
void	fireDeleteEvent(String eventType, String dataType, Object data) Fires a data change event about the deletion of some resource (object).
void	fireSnapshotEvent(String eventType, String dataType, Object data) Fires a data change event with a snapshot of some resource (object).
void	fireUpdateEvent(String eventType, String dataType, Object data) Fires a data change event about an update of some resource (object).

Method Detail

fireCreateEvent

void fireCreateEvent(String eventType,
                     String dataType,
                     Object data)

Fires a data change event about a creation of some resource (object).

Parameters:

eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.

dataType - the content of the data_type field of the Nakadi event.

data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the resource which was created. It will be used as content of the data field of the Nakadi event.

fireUpdateEvent

void fireUpdateEvent(String eventType,
                     String dataType,
                     Object data)

Fires a data change event about an update of some resource (object).

Parameters:

eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.

dataType - the content of the data_type field of the Nakadi event.

data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the new state of the resource which was updated. It will be used as content of the data field of the Nakadi event.

fireDeleteEvent

void fireDeleteEvent(String eventType,
                     String dataType,
                     Object data)

Fires a data change event about the deletion of some resource (object).

Parameters:

eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.

dataType - the content of the data_type field of the Nakadi event.

data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the last state (before the deletion) of the resource which was deleted. It will be used as content of the data field of the Nakadi event.

fireSnapshotEvent

void fireSnapshotEvent(String eventType,
                       String dataType,
                       Object data)

Fires a data change event with a snapshot of some resource (object).

This notifies your consumers about the current state of a resource, even if nothing changed. Typical use cases include initial replication to new consumers or hotfixes of data inconsistencies between producer and consumer.

Normally applications don't have to call this themselves, instead they should implement the SnapshotEventProvider interface to add support for snapshot creation via the actuator endpoint.

Parameters:

eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.

dataType - the content of the data_type field of the Nakadi event.

data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the current state of the resource. It will be used as content of the data field of the Nakadi event.

fireBusinessEvent

void fireBusinessEvent(String eventType,
                       Object payload)

Fires a business event, i.e. an event communicating the fact that some business process step happened. The payload object will be used as the main event content (just metadata will be added). Same as for data change events, you should call this method in the same transaction as you are storing related changes into your database.

Parameters:

eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.

payload - some POJO that can be serialized into JSON (required parameter)