Buy Used Car Example:

For the model above we will walk-through how to execute it programaticaly.

Using bpmn-server from bpmn-client package

Make sure you have installed 'bpmn-client' using npm install bpmn-client

const { BPMNServer } = require('bpmn-client');

test();

async function test() {

    const API_KEY = '12345';

    const HOST = 'localhost';
    const PORT = '3000';

    const BASE_URL = 'api';

    const client = new BPMNClient(HOST, PORT, API_KEY);
// or if you had .net setup you could use:

   const client = new BPMNClient(process.env.HOST, process.env.PORT, process.env.API_KEY);

    const engine = server.engine;

The server object provides a set of components;for now, we need the engine We start a process execution by name; in this case 'Buy Used Car' BPMN definitions are saved our catalog as defined by the configuration, in our WebApp they are under WebApp/processes folder

let response = await engine.start('Buy Used Car');

the above will go through all the bpmn elements and pause at our User Task

let us get the items; items are the instances of various nodes executed so far

const items = response.items.filter((item) => {
  return item.status == 'wait';
});

items.forEach((item) => {
  console.log(`  waiting for <${item.name}> -<${item.elementId}> id: <${item.id}> `);
});
const itemId = items[0].id;

console.log(`Invoking Buy id: <${itemId}>`);

We now need to specify which node to invoke, keep in mind this can happen any time later so we need to identify the instance as well as the item, but since the ItemId is unique we can use it for the query.

The query is passed to MongoDB to select the appropriate item.

const input = { model: 'Thunderbird', needsRepairs: false, needsCleaning: false };
response = await engine.invoke({ items: { id: itemId } }, input);

console.log('Ready to drive');

keeping in mind that the bpmn definition defines conditional flow as such:

<bpmn:sequenceFlow id="flow_gw1_clean" sourceRef="gateway_1" targetRef="task_clean">
    <bpmn:conditionExpression xsi:type="bpmn:tExpression"><![CDATA[
    (this.needsCleaning=="Yes")
    ]]></bpmn:conditionExpression>
</bpmn:sequenceFlow>

in the next step, we will query on instance id as well as the element id

response = await engine.invoke({ instance: { response.execution.id }, items: {elementId: 'task_Drive' }});

console.log(`that is it!, process is now complete status=<${response.execution.status}>`)

The instance Items should look like this: