Event Stream Format

MIME type: text/event-stream

ID: eventstream

DataWeave represents the Event Stream as an Array of Object, where each value is a String. The output type is Array<{_:String}>, where each key represents a field in the event.

Examples

These examples show uses of the event stream format.

Example: Simple Server Event Input
Example: Ignoring Spaces After the Colon

Example: Simple Server Event Input

This example shows how DataWeave represents a simple server event input.

Input

This stream contains four blocks. The first block has one comment, and fires no events. The second block has two fields with names data and id respectively; an event is fired with the data first event and sets the last event ID to 1. The third block fires an event with the data second event; it also has an id field with no value, which resets the last event ID to an empty string. The fourth block contains a data field with the value third event, which fires an event.

: test stream

data: first event
id: 1

data:second event
id

data:  third event

Source

The DataWeave script transforms this input into the given output.

%dw 2.0
output application/json
---
payload

Output

The JSON format outputs these three events.

[
  {
    "data": "first event",
    "id": "1"
  },
  {
    "data": "second event",
    "id": ""
  },
  {
    "data": "third event"
  }
]

Example: Ignoring Spaces After the Colon

This example shows that spaces after the colon are ignored if present.

Input

myInput.sse:

data:test

data: test

Source

This process transforms the input into JSON.

%dw 2.0

output application/json
---
payload

Output

The JSON output is an Array of the valid Object from the server event input.

[
  {
    "data": "test"
  },
  {
    "data": "test"
  }
]

Configuration Properties

DataWeave supports these configuration properties for this format.

Reader Properties

This format has no reader properties.

Writer Properties

This format accepts properties that provide instructions for writing output data.

Parameter Type Default Description

Parameter	Type	Default	Description
`bufferSize`	`Number`	`8192`	Size of the buffer writer, in bytes. The value must be greater than `8`.
`deferred`	`Boolean`	`false`	Generates the output as a data stream when set to `true`, and defers the script’s execution until the generated content is consumed. Valid values are `true` or `false`.

bufferSize

Number

8192

Size of the buffer writer, in bytes. The value must be greater than 8.

deferred

Boolean

false

Generates the output as a data stream when set to true, and defers the script’s execution until the generated content is consumed.

Valid values are true or false.

Supported MIME Types

This format supports this MIME type:

text/event-stream