How to create REST API on API Gateway on

Before you begin, make sure you have the following prerequisites in place:
webMethods Integration Server (on-premises): Ensure you have webMethods Integration Server installed and configured in your on-premises environment.
webMethods.io Integration: Sign up for an account on webMethods.io Integration (if not already done) and have the necessary credentials ready.
Postman: Install Postman to test the API.
Now, let's proceed with the steps:
Step 1: Design Your API
Design Your API: Decide on the API endpoints and the structure of the requests and responses for the calculator operations (add, subtract, multiply, divide). You can use RAML or Swagger/OpenAPI for designing your API.
Step 2: Implement the API on webMethods Integration Server (on-premises)
Create Integration Services: In webMethods Integration Server, create Integration Services for each calculator operation (add, subtract, multiply, divide).
Define Input/Output Documents: Define the input and output document structures for each service. These structures should match your API design.
Implement Services: Write the service logic for each calculator operation. For example, for addition, your service should take two input parameters, perform the addition, and return the result.
Expose as REST Services: Expose each service as a RESTful service using the Integration Server's built-in RESTful capabilities. Configure the REST resources, methods, and paths according to your API design.
Step 3: Publish API to webMethods.io Integration
Export WSDL or Swagger: Export the WSDL (for SOAP services) or Swagger/OpenAPI definition (for REST services) of your Integration Services from webMethods Integration Server.
Import to webMethods.io Integration: In your webMethods.io Integration account, create a new project or integration flow.
Use Connector: Use the appropriate connector (e.g., SOAP Connector for WSDL or REST Connector for Swagger/OpenAPI) to import the exported definition into webMethods.io Integration.
Map Inputs/Outputs: Map the inputs and outputs of your Integration Services to the connector's inputs and outputs within webMethods.io Integration.
Deploy Integration: Deploy the integration within webMethods.io Integration, which makes it accessible via a cloud-based URL.
Step 4: Test the API Using Postman
Retrieve API Endpoint: In webMethods.io Integration, find the endpoint URL for your deployed API.
Open Postman: Open Postman and create a new request.
Set Request Details: Set the request type (GET, POST, etc.), enter the API endpoint URL, and provide the necessary request parameters.
Send Request: Click "Send" to send the request to your webMethods.io Integration API.
Review Responses: Check the responses from the API to ensure that the calculator operations are working as expected.
By following these steps, you can create a REST API provider for your calculator program using webMethods Integration Server and webMethods.io Integration, and then test it using Postman. Be sure to customize the instructions based on your specific use case and tool versions.