REST.API call

Warning

Make sure your working environment is properly configured.

Operation state can be added in the workflow to execute REST.API call, get the result and apply transformations on it.

This tutorial explains how to make REST.API call in your workflow. Before starting, open the portal and edit a workflow.

Add a Workflow function

According to the Serverless Workflow specification, workflow function is a reusable definition for service invocation and/or expression evaluation. It can be referenced by its identifier inside the workflow states.

In the workflow edition view, click on the Functions Functions button. A popup will be displayed, fill-in the form like this and click on the Add button.

  • Name: Name of the function for example : GetDogFacts.
  • Type: Select the type of function : RESTFul service invocation.
  • Operation: Enter the API url or the OPENAPI url for example : http://dog-api.kinduff.com/api/facts.

Functions editor

Add an Operation state

Drag and drop the Operation state into the workflow. Edit its properties and add a new action by clicking on the text field Actions to be performed.

Add action

A popup will be displayed, fill-in the form like this and click on the Add button.

  • Name : Name of the action : GetDogFact.
  • Use results : If set to false, action data results are not added/merged to state data. Default must be true.
  • Filter data results: Workflow expression that filters the actions data results for example: .facts[0].
  • Select state data element Workflow expression that selects a state data element to which the action results should be added/merged into for example : .firstFact.
  • Type : Select the type of action : Function.
  • Arguments : Arguments (input) passed to the referenced function.

Popup action

Execute operation

When the workflow is executed :

  1. The operation state is going to fetch the result from the API : { "facts": ["Dogs do not have an appendix."], "status": true }.
  2. The JSON result is transformed by the results expression : the incoming JSON { "facts": ["Dogs do not have an appendix."], "status": true } becomes "Dogs do not have an appendix.".
  3. The transformed JSON is added into the state data, the destination is specified by the toStateData parameter. The state should look like to something like this { "firstFact" : "Dogs do not have an appendix." }.

Workflow result

YAML file :

id: 531a4b36-46f5-4406-b77a-1f9c50998668
version: 4
name: GetAllDogFact
description: GetAllDogFact
start:
  stateName: b73b7168-d47c-4c2a-a0ce-0670e14a0aa8
states:
  - id: b73b7168-d47c-4c2a-a0ce-0670e14a0aa8
    name: operation
    type: operation
    actionMode: sequential
    end: true
    actions:
      - name: GetDogFact
        functionRef:
          refName: GetDogFact
        actionDataFilter:
          useResults: true
          results: ${ .facts[0] }
          toStateData: ${ .firstFact }
functions:
  - name: GetDogFact
    type: rest
    operation: http://dog-api.kinduff.com/api/facts

The workflow definition can be replaced by cliking on the button YAML.