Creating SAP CAPM Demo Project and Custom Functions Your Complete Hands On Tutorial
Posted on August 11, 2025 by Laeeq Siddique
Introduction:
Understanding SAP CAPM Custom Functions
SAP CAPM Custom Functions. This is about the capability to define and use your logic in the SAP Cloud Application Programming Model (CAPM). CAPM itself is a great platform offering an easy way to create enterprise-level services in SAP, end-to-end.
This blog covers :
- Creating a CAPM demo project
- Bound and Unbound Custom Functions Specification and Implementation of Bound and Unbound Custom Functions
- Inject flexible business logic with JavaScript
- Developing SAP API and corresponding real-world service endpoints
This guide by Cremencing is the perfect resource for both SAP beginners and seasoned professionals. As a premier provider of SAP custom development, Cremencing helps you go beyond the basics—offering expert insights into what you need to know during the development process. With best practices and real-world examples, this book will show you how to take your application to the next level.
What is SAP CAPM?
SAP Cloud Application Programming Model (CAPM) is a development framework designed for building full-stack applications within the SAP ecosystem. It supports Node.js and Java runtimes and is used to develop multi-target applications (MTAs) across the following layers:
| Layer | Description |
| DB Layer | Runs in SAP HANA |
| Service Layer | Runs in Node.js or Java |
| UI Layer | Runs in the browser (Fiori, SAPUI5, etc.) |
Steps to Create a CAPM Demo Project
You can create a CAPM project either through the CLI in VS Code or via the wizard in SAP Business Application Studio (BAS).
Option 1: Using Command Line Interface (CLI)
cds init my-capm-project
cd my-capm-project
npm install
Option 2: Using SAP BAS Wizard
- Log in to SAP BAS
- Start a new project from the template: “Basic CAP Project”
- Include sample data (optional)
- Wait for the project scaffolding to be completed
Project Structure Overview
| Folder/Files | Purpose |
| db/ | Data model definitions (e.g., data-model.cds) |
| srv/ | Service definitions & logic (.cds, .js files) |
| app/ | Optional UI layer |
| package.json | Project metadata and dependencies |
| cdsrc.json | CAPM configurations |
| gen/ | Auto-generated content for builds |
After initializing, use cds watch to start the server and auto-refresh upon changes. Your CAPM application will be live on http://localhost:4004.
Implementing SAP CAPM Custom Functions
What Are Custom Functions?
Custom functions in SAP CAPM are used to encapsulate reusable business logic that goes beyond standard CRUD operations. They can be either Bound to specific entities or Unbound and globally accessible across the service.
Bound Functions
Bound functions are directly linked to a data entity and are often used for entity-specific computations or logic.
Step 1: Define the Function in .cds
File: srv/custservice.cds
entity Customer {
ID: UUID;
name: String;
}
function boundedFunction(msg: String): String;
Step 2: Implement the Function in .js
File: srv/custservice.js
module.exports = (srv) => {
srv.on(‘boundedFunction’, async (req) => {
const { msg } = req.data;
return `Bound Function Response: ${msg}`;
});
};
Step 3: Call the Function via URL
http://localhost:4004/api/customer/CustService.boundedFunction(msg=’Welcome’)
Unbound Functions
Unbound functions are service-level operations that do not rely on specific entities.
Step 1: Define the Function in .cds
function greetUser(name: String): String;
Step 2: Implement the Function in the .js
module.exports = (srv) => {
srv.on(‘greetUser’, async (req) => {
return `Hello, ${req.data.name}`;
});
};
Step 3: Call the Function via URL
http://localhost:4004/api/greetUser(name=’SAP Developer’)
Running & Testing the CAPM Project
Use the following command to run and observe your custom functions:
cds watch
Visit http://localhost:4004 to view available services. Each custom function you’ve defined will be exposed as an endpoint and can be tested using any REST client (like Postman) or directly from the browser.
Key Differences: Functions vs. Actions in CAPM
| Feature | Functions | Actions |
| Side Effects | No (read-only) | Yes (can update data) |
| Input Params | Supported | Supported |
| Return | A single response value | Can trigger workflow or process |
| Example Use | Calculations, read-only queries | Approve Order, Cancel Subscription |
Use functions when you need to return a value without modifying data. Use actions when your logic causes data changes or business events.
Competitive Comparison
| Feature | Cremencing Blog | Competitor 1 | Competitor 2 | Competitor 3 |
| Full CAPM setup guide | Yes | Yes | Yes | Yes |
| Custom function implementation | Yes (detailed) | No | Partial | Yes |
| Service structure explained | Yes | No | Yes | Yes |
| CLI and BAS wizard both covered | Yes | Yes | No | Yes |
Cremencing.com offers deeper, practical steps, real-world function implementations, and structural-level clarity that competitors often skip.
Resources
Official SAP Documentation
Community Articles and Code Examples
Internal Link
Need custom help with SAP? Explore Cremencing’s expert SAP Custom Development Services.
Conclusion
Knowing how to create and use SAP CAPM Custom Functions is a powerful capability that allows you to create customized solutions in the SAP landscape. Whether you’re describing bound functions for entity-level operations or unbound functions for general-purpose use, CAPM empowers you to scale and tame your service layer in a way that wasn’t possible before.
You now know:
- How to create a CAPM demo project
- The folder organization and function locations
- Writing and calling custom logic with JS
- What are the best use cases for bound vs unbound functions
For companies that want to inject additional intelligence, automation, or custom processes into their SAP systems, custom development with CAPM is the way forward.
Call to Action
If you are interested in building powerful and custom applications in SAP with CAPM, Cremencing Solution is here to help!
We are an SAP Custom Development services company, offering industrial-strength, scalable SAP-based solutions designed to fit your business like a glove.
Ready to discuss your next project?
Visit our Contact Page or explore our SAP Custom Development Services to learn more.
FAQs
1. What are the steps involved in creating a demo project using SAP Cloud Application Programming Model (CAPM)?
Start by running cds init, define your data and service layers, install dependencies using npm install, and use cds watch to launch the application.
2. How can you define and use custom functions in a CAPM service layer?
You define the function in a .cds file and implement the logic in a .js file of the same name within the srv/ folder.
3. What is the role of the srv folder in an SAP CAPM project?
The srv folder houses your service definitions and business logic, including custom functions and actions.
4. How does the CAPM framework support the implementation of custom business logic?
CAPM allows the use of JavaScript or Node.js modules for service handlers via the srv.on() method, offering flexibility and async handling.
5. What is the difference between actions and functions in CAPM?
Functions are read-only and return data, while actions can modify data or trigger workflows. Use functions for calculations and actions for processing.