Call an External API

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Call an External API

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Call an External API

Requires Customer/Partner License

Julie Plummer

09/16/2019

Intermediate

30 min.

Point to an external API and display its output in the console.

You will learn

How to create a new destination for an existing communication arrangement
How to call an external API from inside an ABAP system

Predefined communication scenarios allow you to, for example, exchange data between a SAP Cloud Platform system and an external system.
A communication arrangement specifies the metadata for a communication scenario. For more information, see Maintain a Communication Arrangement for an Exposed Service.

You will create a new destination for an existing communication arrangement, specifying the URL for an external API, user/password, and authentication.
You will then create a class that calls the API and displays the output from it in the console.

Throughout this tutorial, objects name include the suffix XXX. Always replace this with your group number or initials.

Step 1: Open the instance of the destination service

In your space in the SAP Cloud Platform Cockpit (e.g. Dev), open Service Marketplace and choose Destination.
Choose Instances, then choose your instance, EXTERNAL_API_XXX.

Done

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Step 2: Create a new destination

From the left pane, choose Destinations, then choose New Destination:
Then enter the following (replacing xxx with your group number). Then choose Save:
- Name = Z_STREETMAP_XXX
- URL = https://nominatim.openstreetmap.org/
- Proxy type = Internet
- Authentication = NoAuthentication

Done

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Step 3: Create an ABAP class

Now, you will create an ABAP class that will call your destination, and which you can run in the console.

In the ABAP Development Tools (ADT), in the Package Explorer, select your package and choose New > ABAP Class from the context menu.
Enter a name and description for your class and choose Next. Remember to change XXX to your group number.
Choose or create a transport request, then choose Finish.

The class is displayed in a new editor.

Done

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Step 4: Add an INTERFACES statement

View Full Instructions

Add the following interfaces statement to the public section:

PUBLIC SECTION.
  INTERFACES if_oo_adt_classrun.
PRIVATE SECTION.

This enables you to run the class in the console.

Done

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Step 5: Implement the method

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Add the method implementation below and wrap it in an exception.
Then replace the xxx of i_name and i_service_instance_name with your group number.
(To get the i_service_instance_name, see the tutorial Create a Communication Arrangement for Outbound Communication, step 7).

METHOD if_oo_adt_classrun~main.
    TRY.
        DATA(lo_destination) = cl_http_destination_provider=>create_by_cloud_destination(
          i_name                  = 'Z_STREETMAP_XXX'
          i_service_instance_name = 'OutboundComm_for_RFCDemo_XXX'
          i_authn_mode = if_a4c_cp_service=>service_specific ).

        DATA(lo_http_client) = cl_web_http_client_manager=>create_by_http_destination( i_destination = lo_destination ).
        DATA(lo_request) = lo_http_client->get_http_request( ).



        DATA(lo_response) = lo_http_client->execute( i_method = if_web_http_client=>get ).
          out->write( lo_response->get_text( ) ).

      CATCH cx_root INTO DATA(lx_exception).
        out->write( lx_exception->get_text( ) ).
    ENDTRY.
  ENDMETHOD.

Done

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Step 6: Check, save, and activate

Check your syntax (Ctrl+F2).
Save (Ctrl+S) and activate (Ctrl+F3) your class.

Done

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Step 7: Run the class in the console

Run your class in the console (F9).

The output should look something like this:
Image depicting step-9-console

Done

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Step 8: Add formatting

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The output is currently just an HTML dump. You will now format the output as JSON.

Immediately after the DATA(lo_request) = lo_http_client->get_http_request( ). statement, add the following code:


lo_request->set_form_field(
    i_name  = 'format'
    i_value = 'json' ).
lo_request->set_form_field(
    i_name  = 'q'
    i_value = 'SAP SE' ).
lo_request->set_form_field(
    i_name  = 'country'
    i_value = 'Germany' ).
lo_request->set_form_field(
    i_name  = 'city'
    i_value = 'Walldorf' ).
lo_request->set_form_field(
    i_name  = 'addressdetails'
    i_value = '1' ).

Done

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Step 9: Check, save, activate, and test