Add Business Logic to Your Application

In this tutorial, you add some custom code to the CAP application. Depending on the value of the property impact, the custom code changes the value of the property criticality. This property is used in OData annotations to control the color of some of the cells in the table of our work list page.

1. Copy the file risk-service.js from templates/cap-business-logic/srv to the srv folder of your app.

2. In your browser, reload the page of the SAP Fiori elements app.

   It now shows our work list with the columns Priority and Impact with color and an icon, depending on the amount in Impact.

   

const cds = require('@sap/cds')
/**
 * Implementation for Risk Management service defined in ./risk-service.cds
 */
module.exports = cds.service.impl(async function() {
    this.after('READ', 'Risks', risksData => {
        const risks = Array.isArray(risksData) ? risksData : [risksData];
        risks.forEach(risk => {
            if (risk.impact >= 100000) {
                risk.criticality = 1;
            } else {
                risk.criticality = 2;
            }
        });
    });
});

Because your file is called risk-service.js and, therefore, has the same name as your application definition file risk-service.cds, CAP automatically treats it as a handler file for the application defined in there. CAP exposes several events and you can easily write handlers like the above.

In this case, the event after is triggered after a READ was carried out for our Risks entity. In your custom handler, you get all the data (in this case, all the risks) that was read according to the query. You can loop over each of them and, if needed, adjust the data of the response. In this case, you change the value of the criticality when the impact is bigger than 100000. The new values for criticality are then part of the response to the read request.

So, this affects the application’s response, but how does it translate into a changed UI? For this, you have got to go back to the annotations you created in Create a CAP-Based Application where you find your srv/risks-service-ui.cds file. There, you had the two columns prio and impact annotated with an additional Criticality annotation. This annotation points to the criticality property of your application.

Criticality with an upper case C is the annotation, while the property name criticality could also be called different opposed to the annotation.

As you now set different values in your custom handler for criticality, the SAP Fiori elements app translates them into icons and colors, which you can see in the UI.

annotate RiskService.Risks with @(
    UI: {
        ...
        ...
        LineItem: [
            ...
            ...
            {
                Value: prio,
                Criticality: criticality
            },
            {
                Value: impact,
                Criticality: criticality
            }
        ],

You can find more about the possible values of the Criticality annotation in section UI Vocabulary. This, however, is just one of the many sections of the OData annotation vocabularies for UI and Common usage.

The result of this tutorial can be found in the cap-business-logic branch.