Data objects

A data object in the diagram stands for data the process works on: a client, an order, a policy. bpmn-server asks the application for it when an element connected to it runs, and keeps it in the instance data.

In the model

Draw a data object, name it (client), and connect it to the element that needs it with a data association, either way (input or output). Typically the start event, or the first task that needs the data.

In the application

The application delegate loads it:

import { DefaultAppDelegate } from 'bpmn-server';

class MyAppDelegate extends DefaultAppDelegate {
    async loadDataObject(name: string, item) {
        if (name == 'client')
            return await clients.findOne({ id: item.data.clientId });
    }
}

name is the data object's name in the diagram; item is the element running, with the instance data in item.data.

The value is put in the instance data under that name, data.client, and saved with the instance like any data. Later elements read and change it: $data.client.name in an expression, this.data.client in a script.

It is loaded each time a connected element runs, after the element's enter and before its start, so the element's own scripts already see it.

Checks

verifyModel:

• data-object-not-loaded: a data object connected to nothing, so it is never loaded.
• no-data-object-loader: the model has data objects, but the application's delegate has no loadDataObject.

Coming next: data stores

A data object is loaded into the instance and saved with it. A data store will stand for data the process queries without keeping it, read where it lives each time. Until then, a data store reference connected to an element is loaded the same way as a data object.