Calling a Remote OData API from a Local CAP Java Project

This article provides a step-by-step guide on how to call a remote OData API from a local CAP Java project. The process involves setting up a CAP Java project, adding required libraries, fetching OData metadata and generating a CSN file, configuring connectivity settings, and defining the service model and handler. The article focuses on calling the SAP S/4HANA sandbox OData API to retrieve a list of business partners.

In today's digital landscape, integrating various enterprise systems through APIs is a common practice. This article provides a step-by-step guide on how to call a remote OData API from a local CAP Java project. The focus is on utilizing the SAP S/4HANA sandbox OData API to retrieve a list of business partners.

Step-by-Step Guide

# 1. Testing Environment Setup
To begin, set up your testing environment. This includes using the SAP Business Accelerator Hub – Sandbox, SAP BTP Trial, and the IDE Visual Studio Code. Ensure you have the necessary tools installed, such as Maven 3.9 and OpenJDK 21.

# 2. Project Initialization
Initialize a CAP Java project using the command:
```shell
cds init cap-java-remote-api --add destination,xsuaa --java
```
This command sets up the project structure and initializes the necessary configurations.

# 3. Adding Required Libraries
To call a remote OData service, you need the SAP Cloud SDK and the CAP library for remote OData. Add the latest SDK version to your project's properties and the Cloud SDK BOM to the root `pom.xml`. Additionally, add the necessary dependencies to `srv/pom.xml`.

# 4. Fetching OData Metadata and Generating CSN
Download the Business Partner (A2X) EDMX file from the SAP Business Accelerator Hub and place it in your project’s root folder. Generate a `.csn` file using the `cds import` command.

# 5. Connectivity Configuration
Configure the BTP Destination Service to store the connectivity settings. For sandbox environments, authentication is done via an API Key stored in a local `.env` file. Add the destination in `application.yaml` and ensure the API Key is correctly referenced.

# 6. Service Model and Handler
Define the service model in `srv/business-partner-service.cds` using the imported EDMX file. Implement the handler in `srv/src/main/java/customer/cap_java_remote_api/handlers/BusinessPartnerHandler.java` to handle the API calls.

# 7. Preparing for Deployment
Generate an MTA descriptor and build the project. Ensure all dependencies are correctly added to `srv/pom.xml`.

# 8. Deploying to BTP
Create an `.mtar` file and deploy it to the SAP BTP environment. Verify the deployment in the BTP Cockpit.

# 9. Accessing the Remote API Locally
Bind the xsuaa and destination services locally and run the application in hybrid mode. Access the endpoint to retrieve the list of business partners.

Conclusion
By following these steps, you can successfully call a remote OData API from a local CAP Java project. This guide provides a clear and detailed pathway to integrate SAP S/4HANA sandbox OData API into your local development environment.

References
[1] https://community.sap.com/t5/technology-blog-posts-by-sap/how-to-call-a-remote-odata-api-from-your-local-cap-java-project/ba-p/14177098