Event data structure

  1. TOC {:toc}

Overview

The Event data structure is the representation of a CloudEvent in sdk-go. The main features are:

  • Support for multiple event versions
  • Type safe implementation of CloudEvents attributes and extensions
  • Validation of the event
  • Implementation of marshalling/unmarshalling to JSON.
  • Implementation of data field codecs

Writing/Reading the attributes and extensions

To read and write attributes and extensions of the Event, you can use the methods of EventContextReader/EventContextWriter:

ev := cloudevents.NewEvent()
err := ev.Context.SetSource("http://localhost")

ev := cloudevents.NewEvent()
err := ev.Context.SetExtension("aaa", "hello_world")

Attributes and extensions are represented internally using wrapper types from types module.

Writing/Reading the data field

To write the data field in your Event, use Event.SetData(). This method accepts both the content type and the payload. If the payload is a []byte, then no encoding will be made, otherwise the datacodec module will be used to encode the payload.

You can read the data or accessing directly to the underlying []byte using Event.Data() or decoding it using event.DataAs(), which uses a specific Decoder from datacodec module to decode the event data.

Some formats have built-in support in datacodec, like application/xml, application/json and text/plain. You can use your own encoding implementing datacodec.Encoder and datacodec.Decoder and registering it with datacodec.AddEncoder and datacodec.AddDecoder

Marshal/Unmarshal event to JSON

To marshal the Event to JSON:

ev := cloudevents.NewEvent()
bytesArray, err := json.Marshal(event)

To unmarshal the Event from JSON:

ev := &event.Event{}
err := json.Unmarshal(bytesArray, ev)