Create Your First Application with SAP Cloud SDK for JavaScript

Initially, the app only contains the index and hello-world routes. We will add another route for business-parters that will list all available business partners.

First, create a new file business-partner.controller.ts in the src/ directory and add an implementation for this route, like so:

import { Controller, Get } from '@nestjs/common';

@Controller()
export class BusinessPartnerController {
  @Get('business-partners')
  getBusinessPartners() {
    return 'We will implement this in a minute.';
  }
}

The @Controller() decorator marks our class as controller (i.e. a thing that handles requests), and the @Get('business-partners') decorator marks the getBusinessPartners method as handler for GET requests on the path /business-partners. The @Controller() decorator allows providing more configuration, but this is beyond the scope of this tutorial.

In order for the controller to work, we also need to register it in our application. Open app.module.ts, import the controller class you just created and add it to the controllers declaration. Your file should look like this:

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { BusinessPartnerController } from './business-partner.controller';

@Module({
  imports: [],
  controllers: [AppController, BusinessPartnerController],
  providers: [AppService],
})
export class AppModule {}

If you’ve started your application the following command in the previous tutorial, it should detect the change and restart automatically.

npm run start:dev

If you’ve terminated your application, you can restart it by running the start command again. Now, calling http://localhost:8080/business-partners should return our placeholder string.

In order to use the SAP Cloud SDK for JavaScript to make a call to an OData service, add the virtual data model (VDM) for this service to your dependencies. For this tutorial we are using the VDM for the business partner service. Install it with the following command:

npm install @sap/cloud-sdk-vdm-business-partner-service

Import the entity you want to make a call to into your application. In this tutorial we are importing the business partner entity of the business partner service. Add the following line to the top of the business-partner.controller.ts.

import { BusinessPartner } from '@sap/cloud-sdk-vdm-business-partner-service';

Now the BusinessPartner entity is available for you to be used.

Side-note: The SAP Cloud SDK for JavaScript offers packages for each OData service exposed by SAP S/4HANA Cloud. You can find a list of these services in the SAP API Business Hub and a list of the corresponding packages in our documentation.

In business-partner.controller.ts create a function getAllBusinessPartners and implement it depending on your API Server:

function getAllBusinessPartners(): Promise<BusinessPartner[]> {
  return BusinessPartner.requestBuilder()
    .getAll()
    .execute({
      url: 'http://localhost:3000'
    });
}

function getAllBusinessPartners(): Promise<BusinessPartner[]> {
  return BusinessPartner.requestBuilder()
    .getAll()
    .execute({
      url: '<URI of your SAP S/4HANA Cloud System>',
      username: '<USERNAME>',
      password: '<PASSWORD>'
    });
}

function getAllBusinessPartners(): Promise<BusinessPartner[]> {
  return BusinessPartner.requestBuilder()
    .getAll()
    .withCustomHeaders({ APIKey: '<YOUR-API-KEY>'})
    .execute({
      url: 'https://sandbox.api.sap.com/s4hanacloud'
    });
}

• We apply requestBuilder on the business partner entity. Every entity has a requestBuilder function that allows to chain all types of request builders that are available for this entity.
• We use the GetAll request builder to create a request that retrieves all of the business partners.
• The SAP Cloud SDK automatically sets some necessary request headers on every request, but you can specify additional custom headers using the withCustomHeaders function.
• The last step when making a request is the request execution, chain the execute function and pass a destination to it. It can contain information like an URL, Authentication and Proxy Settings.

As network requests are asynchronous by nature, the return value of this function is a Promise to a list of Business Partners (Promise<BusinessPartner[]>).

Let’s add the execution of this request to getBusinessPartners method:

import { Controller, Get, HttpException } from '@nestjs/common';
import { BusinessPartner } from '@sap/cloud-sdk-vdm-business-partner-service';

@Get('business-partners')
getBusinessPartners() {
  return getAllBusinessPartners()
    .catch(error => {
      throw new HttpException(`Failed to get business partners - ${error.message}`, 500);
    });
}

nest.js will handle the Promise we return automatically. We add a .catch handler to specify how errors are handled (otherwise it would only show “internal server error” when something goes wrong). Here is what your business-partner.constroller.ts should look like, if you are using the mock server:

import { Controller, Get, HttpException } from '@nestjs/common';
import { BusinessPartner } from '@sap/cloud-sdk-vdm-business-partner-service';

@Controller()
export class BusinessPartnerController {
  @Get('business-partners')
  getBusinessPartners() {
    return getAllBusinessPartners()
      .catch(error => {
        throw new HttpException(`Failed to get business partners - ${error.message}`, 500);
      });
  }
}

function getAllBusinessPartners(): Promise<BusinessPartner[]> {
  return BusinessPartner.requestBuilder()
    .getAll()
    .execute({
      url: 'http://localhost:3000',
    });
}

Reload the http://localhost:8080/business-partners url to retrieve a list of business partners.

Congratulations, you just made your first call with the SAP Cloud SDK!

In order to not repeat your destination configuration for every request execution, you can set a destinations environment variable to manage your destinations. In Node.js application, it is common to use a .env file to maintain such environment variables for a given project. Create a .env file in the root directory of your project and define the destinations environment variable as follows:

destinations=[{"name": "<DESTINATIONNAME>", "url": "<URL to your system>", "username": "<USERNAME>", "password": "<PASSWORD>"}]

This is what it would look like for the mock server:

destinations=[{"name": "MockServer", "url": "http://localhost:3000"}]

Now that we have defined our destinations, we need to make sure that they are available in our process. For this we use the config package provided by nest.js. You can install it with the following command:

npm install @nestjs/config

In order to load the environment variables defined in the .env file, we need to add the ConfigModule provided by the config package to the application’s @Module definition. Open app.module.ts and update it with the following code:

import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { BusinessPartnerController } from './business-partner.controller';

@Module({
  imports: [ConfigModule.forRoot()],
  controllers: [AppController, BusinessPartnerController],
  providers: [AppService],
})
export class AppModule {}

In line 2, ConfigModule is imported from the config package and in line 8 we add it to the module’s imports. If no arguments are passed to the forRoot() method, the .env file has to be located in the project root. For details on the possible configuration see the nest documentation. To reference a destination in the request execution, simply replace the url with a destinationName - MockServer in our example:

function getAllBusinessPartners(): Promise<BusinessPartner[]> {
  return BusinessPartner.requestBuilder()
    .getAll()
    .execute({
      destinationName: 'MockServer'
    });
}

Note, that every environment variable in the .env file has to be defined on one line. You can add more destinations to the array.