just-events

Library for easy handling of JSON events in microservices.

Event structure

Each event has the following structure:

{
  "id": "0b3b998d-65da-41a2-9f2a-f8ea7187d571",
  "timestamp": "2019-01-01T00:00:00Z",
  "name": "some.event",
  "payload": {
    "foo": "bar"
  }
}

Usage

Payload class

Event is represented by Event<P extends Payload> class, where P is the event payload type defined by the library user.

You need to define some POJO that implements the Payload interface, e.g.:

package com.github.wpik.justevents.events;

import com.github.wpik.justevents.Payload;
import lombok.Builder;
import lombok.Data;

import javax.validation.constraints.NotBlank;

@Data
@Builder
public class SomePayload implements Payload {
    public static final String NAME = "some.event";

    @NotBlank
    private String foo;

    @Override
    public String getName() {
        return NAME;
    }
}

Bootstrap the library

Then you create the instance of JustEvents class and register the payload with it. After this, you can use that instance to serialize and deserialize events.

JustEvents justEvents=new JustEvents();
justEvents.registerEvent(SomePayload.NAME, SomePayload.class);

Serialization

To serialize event, create it and use JustEvents.serialize() merhod:

Event<?> event = Event.builder()
    .id("686f4edd-e8d6-4f23-a053-046b2ddf60ed")
    .timestamp(OffsetDateTime.parse("2019-01-01T12:00:00Z", DateTimeFormatter.ISO_OFFSET_DATE_TIME))
    .payload(SomePayload.builder()
        .foo("bar")
        .build())
    .build();

String json = justEvents.serialize(event);

json will have this value:

{
   "id":"686f4edd-e8d6-4f23-a053-046b2ddf60ed",
   "timestamp":"2019-01-01T12:00:00Z",
   "name":"some.event",
   "payload":{
      "foo":"bar"
   }
}

Deserialization

To deserialize use JustEvents.deserializeEventName() and then JustEvents.deserialize() methods. First method will just deserialize the event name. This is needed if your service may receive some other events that you don't want to process in the service. This way you can check the event name and deserialize it only if you are interested in it.

String json = ...
String eventName = justEvents.deserializeEventName(json);

if("some.event".equals(eventName)){
    Event<SomePayload> event = justEvents.deserialize(json);
    // process event
}