Exercise: Querying SAP APIs in a TypeScript NestJS Application

In this exercise, you will learn how to query the Business Partner API of SAP S/4HANA Cloud. We will use the Mock Server instead of the actual SAP S/4HANA Cloud.

1. Checkout the branch tsnestjs_v1.0_query in SAP Business Application Studio

   1. Run the following commands in the terminal

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      cd ~/projects/cloud-sdk-learning-journey
      git checkout -f tsnestjs_v1.0_query

      

2. Build and run the project

   1. Run the application by executing the following commands in the terminal

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      cd cloudsdk_bp_ts
      npm i
      npm run start:dev

      

3. Make sure that the Mock Server is up and running as described in the related previous exercise.

   1. In case the Mock server is installed but not started, you need to open a new terminal window and run the following commands:

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      cd ~/projects/cloud-s4-sdk-book
      npm run start

4. Query the Business Partner API of SAP S/4HANA Cloud

   1. Open the requests.http file in the cloudsdk_bp_ts folder

   2. Click on Send Request in the requests.http file to submit the GET request for business partners

      

   3. Stop the running application using Ctrl + C in the corresponding terminal window.

5. Optional: Query the Business Partner API of the sandbox in api.sap.com.

   1. Access https://api.sap.com/api/API_BUSINESS_PARTNER. Login and get your API Key.

      

   2. Open .env file in the root folder. Replace the URL property with https://sandbox.api.sap.com/s4hanacloud to retrieve business partners from SAP API Business Hub. Note that you also have to provide the APIKEY

      

   3. Re-build and run the application:

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      cd ~/projects/cloud-sdk-learning-journey/cloudsdk_bp_ts
      npm run start:dev

   4. Re-test the Business Partners query in the requests.http file.

   5. Stop the running application using Ctrl + C in the corresponding terminal window.

6. Optional: code walk-through.

   1. Review code in the following source files:

      File name	Comments on code changes
      business-partner.controller.ts	Code logic is as follows... Annotate the method getBusinessPartners with @Get() to handle the GET method Call the getAllBusinessPartners method of the BusinessPartnerService instance asynchronously
      business-partner.service.ts	Code logic is as follows... Annotate the class BusinessPartnerService with @Injectable() to enable dependency injection Call the getAll method to retrieve the business partners Use the SAP Cloud SDK fluent API method chaining to provide additional parameters Return the list of business partners
      requests.http	Provides various HTTP requests that can be submitted to query the Business Partner API
      commands.txt	Provides various commands that can be run on the terminal

      Note

      Check out the SAP Cloud SDK documentation on Executing an OData GET request using SAP Cloud SDK for JavaScript. https://sap.github.io/cloud-sdk/docs/js/tutorials/getting-started/execute-an-odata-request

7. Optional: Manually re-create the project in ~/projects/cloudsdk_bp_ts .

   1. Create a new project by running the following command in the terminal and install dependencies. Select npm when prompted for the package manager

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      cd ~/projects
      npm i -g @nestjs/cli
      nest new cloudsdk_bp_ts (select npm)
      cd cloudsdk_bp_ts
      npm install -D @sap-cloud-sdk/generator
      npm install @nestjs/config @sap-cloud-sdk/http-client @sap-cloud-sdk/resilience @sap-cloud-sdk/odata-v2

   2. Open the cloudsdk_bp_ts folder in the workspace.

   3. Edit the main.ts file in the src folder to listen on port 8080

      

      

   4. Create a new controller and service by executing the following command

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      cd ~/projects/cloudsdk_bp_ts
      nest g controller business-partner
      nest g service business-partner

   5. Create a folder named service-specifications, at the root of the project (folder cloudsdk_bp_ts).

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      mkdir service-specifications

   6. Browse to the https://api.sap.com/api/API_BUSINESS_PARTNER/overview in a separate tab, then login.

   7. Click on API Specification button and click on the download EDMX button. This will download the API_BUSINESS_PARTNER.edmx file

      

   8. Copy the API_BUSINESS_PARTNER.edmx file into the service-specifications folder

      

   9. Create a file named options-per-service.json in the service-specifications folder. Copy contents from here...

   10. Generate the BusinessPartner service by running the following command

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       npx generate-odata-client --input service-specifications --outputDir services --optionsPerService service-specifications/options-per-service.json

   11. Create or update the following files in the table below

       File name	Type	Contents
       business-partner.controller.ts Path: ~/projects/cloudsdk_bp_ts/src/business-partner	Modified	Copy contents from here...
       business-partner.service.ts Path: ~/projects/cloudsdk_bp_ts/src/business-partner	Modified	Copy contents from here...
       app.module.ts Path: ~/projects/cloudsdk_bp_ts/src	Modified	Copy contents from here...
       .env Path: ~/projects/cloudsdk_bp_ts	New	Copy contents from here... Replace the APIKEY value with your API Key.
       requests.http Path: ~/projects/cloudsdk_bp_ts	New	Copy contents from here...

       

   12. Build and run the project in projects/cloudsdk_bp_ts:

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       cd ~/projects/cloudsdk_bp_ts
       npm i
       npm run start:dev

   13. Stop the running application using Ctrl + C in the corresponding terminal window.