API object - ListCustomers service definition and declaration

This article describes all the necessary steps to define an API object (called APICustomers) and declare inside it a ListCustomers service that returns all the Customer data.

Consider a Knowledge Base containing:

1) A Customer Transaction object:

Customer
{
  CustomerId*
  CustomerName
  CustomerLastName
}  

Note: The Customer Transaction has Automatic data population.

2) An SDT that is a collection with the same structure as the Customer Transaction:

3) A Data Provider object with the logic needed to return all the customer's data:

Note that the Data Provider has the previously defined SDT as the output parameter.

Create an API object (by selecting in the main GeneXus Menu File > New > Object) and name it "APICustomers". Inside its Service Source tab, you have to declare, for each service, a mapping between its external name (exposed as a service) and the internal implementation in the KB (in this example, the CustomerList Data Provider). Look at the following mapping:

Customer{
    ListCustomers(out:&SDTCustomers) => CustomerList(&SDTCustomers);
}

The external service name is ListCustomers; internally, it is solved with the CustomerList Data Provider.

The service source is not allowed to access data. Therefore, you have to use a Data Provider or a Procedure object instead of a For Each command or Business Component.

You could define the following events in the Events tabs, if necessary:

Event Before
    //Some Code if is needed
Endevent

Event After
    //Some Code if is needed
Endevent

Event ListCustomers.Before
    //Some code if is needed
Endevent

Event ListCustomers.After
    //Some Code if is needed
EndEvent

The events execution order would be as follows:

1. Event 'Before'
2. Event 'ListCustomers.Before'
3. ListCustomers method (CustomerList Data Provider)
4. Event 'ListCustomers.After'
5. Event 'After'

You can see all the steps being executed:

See Also

Json Collection Serialization property