curl --request GET \
  --url http://{host}:{port}/{contextPath}/process-instance/{id}/activity-instances \
  --header 'Authorization: Basic <encoded-value>'

import requests

url = "http://{host}:{port}/{contextPath}/process-instance/{id}/activity-instances"

headers = {"Authorization": "Basic <encoded-value>"}

response = requests.get(url, headers=headers)

print(response.text)

const options = {method: 'GET', headers: {Authorization: 'Basic <encoded-value>'}};

fetch('http://{host}:{port}/{contextPath}/process-instance/{id}/activity-instances', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_PORT => "62437",
  CURLOPT_URL => "http://{host}:{port}/{contextPath}/process-instance/{id}/activity-instances",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_HTTPHEADER => [
    "Authorization: Basic <encoded-value>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "http://{host}:{port}/{contextPath}/process-instance/{id}/activity-instances"

	req, _ := http.NewRequest("GET", url, nil)

	req.Header.Add("Authorization", "Basic <encoded-value>")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.get("http://{host}:{port}/{contextPath}/process-instance/{id}/activity-instances")
  .header("Authorization", "Basic <encoded-value>")
  .asString();

require 'uri'
require 'net/http'

url = URI("http://{host}:{port}/{contextPath}/process-instance/{id}/activity-instances")

http = Net::HTTP.new(url.host, url.port)

request = Net::HTTP::Get.new(url)
request["Authorization"] = 'Basic <encoded-value>'

response = http.request(request)
puts response.read_body

{
  "id": "eca75c6b-f70c-11e9-8777-e4a7a094a9d6",
  "parentActivityInstanceId": null,
  "activityId": "invoice:2:e9d77375-f70c-11e9-8777-e4a7a094a9d6",
  "activityType": "processDefinition",
  "processInstanceId": "eca75c6b-f70c-11e9-8777-e4a7a094a9d6",
  "processDefinitionId": "invoice:2:e9d77375-f70c-11e9-8777-e4a7a094a9d6",
  "childActivityInstances": [
    {
      "id": "approveInvoice:eca89509-f70c-11e9-8777-e4a7a094a9d6",
      "parentActivityInstanceId": "eca75c6b-f70c-11e9-8777-e4a7a094a9d6",
      "activityId": "approveInvoice",
      "activityType": "userTask",
      "processInstanceId": "eca75c6b-f70c-11e9-8777-e4a7a094a9d6",
      "processDefinitionId": "invoice:2:e9d77375-f70c-11e9-8777-e4a7a094a9d6",
      "childActivityInstances": [],
      "childTransitionInstances": [],
      "executionIds": [
        "eca75c6b-f70c-11e9-8777-e4a7a094a9d6"
      ],
      "activityName": "Approve Invoice",
      "incidentIds": [
        "648d7e21-f71c-11e9-a725-e4a7a094a9d6"
      ],
      "incidents": [
        {
          "id": "648d7e21-f71c-11e9-a725-e4a7a094a9d6",
          "activityId": "AttachedTimerBoundaryEvent"
        }
      ],
      "name": "Approve Invoice"
    }
  ],
  "childTransitionInstances": [],
  "executionIds": [
    "eca75c6b-f70c-11e9-8777-e4a7a094a9d6"
  ],
  "activityName": "Invoice Receipt",
  "incidentIds": null,
  "incidents": null,
  "name": "Invoice Receipt"
}

{
  "type": "<string>",
  "message": "<string>",
  "code": 123
}