Create and expose a custom CDS view

Navigate to the Extensibility category and press the Custom CDS Views tile to start the application on your Fiori Launchpad.

This brings you to the data source list of the available data sources for Custom CDS Views.
Search for a data source you want to use as a basis and select the data source (1) I_Customer.

This is the primary data source of the new Custom CDS view.

Now execute create (2) to create a new Custom CDS view.

On the general tab enter name YY1_New_Customer and label New Customer.

This step is used to taylor a given CDS View to the needs of a customer.
Now switch to the Field Selection tab and select following fields (1):
- Customer
- CustomerName
- CustomerFullName
- Country
- CityName
- PostalCode
- StreetName
These fields will be available in the custom CDS view.

Now save and publish the view.

Result:
This saves and activates the view.
In case the primary data source is access protected, the new view is protected, too.

Switch back to the general tab to generate an OData Service by checkmarking it.
Afterwards save and publish your change. Now your OData Service is generated.

Result:
Now new service <ViewName>_CDS got created and the service is registered for further usage in the communication scenario.

Go back to Press the Custom Communication Scenarios tile to start the application.

In Custom Communication Scenario add a new Scenario by clicking on new button.

A new window will open where you can define the Name of the New Scenario and its Description.

First you have to click the add button. Afterwards search for New Customer and add YY_NEW_CUSTOMER_CDS as a service.

After adding the service YY_NEW_CUSTOMER_CDS, the result will be shown in the following way:

Now you can publish your Communication Scenario.

If you already have a communication system and user then use them in the following steps.
Otherwise you can create a new communication system and user by making use of the following example.
Therefore go to Step 2: Creating a Communication System and User.
https://blogs.sap.com/2017/05/17/part-viii-custom-business-object-exposure-as-external-web-service-bonus-plan/

Navigate to the Communication Management category and press the Communication Arrangements tile to start the application.

Click on the new button to create a new Communication Arrangement.

You can choose YY1_New_Customer as Scenario and select the create button by clicking the value help.

Now select your Service, like EXTERNAL_SYSTEM as Communication System and save the Communication Arrangement.

After you have saved your Communication Arrangement, the URL will be generated.

Result:
The role containing the authorizations for the service(s) is assigned to a communication user. After this step, you can call the service in a web browser and logon with the communication user. You can consume this service also in tools like Excel using the comm. user logon.

Note: the communication arrangement is a configuration object that is created in test and production system separately.