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Call an External API

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Call an External API
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Call an External API

Requires Customer/Partner License
2019-12-03
Intermediate
30 min.
SAP Cloud Platform, ABAP environment, Intermediate, SAP Cloud Platform, Tutorial, ABAP Development, Cloud
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

Prerequisites

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

  1. In your space in the SAP Cloud Platform Cockpit (e.g. Dev), open Service Marketplace and choose Destination.

    Image depicting step-1a-destination

  2. Choose Instances, then choose your instance, EXTERNAL_API_XXX.

    Image depicting step-1b-external-2
Done
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Step 2: Create a new destination

  1. From the left pane, choose Destinations, then choose New Destination:

    Image depicting step-2a-new-destination

  2. 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
    Image depicting step2c-destination-streetmap-nominatim
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.

  1. In the ABAP Development Tools (ADT), in the Package Explorer, select your package and choose New > ABAP Class from the context menu.

    Image depicting step-4a-create-class

  2. Enter a name and description for your class and choose Next. Remember to change XXX to your group number.

    Image depicting step-4b-name-class

  3. Choose or create a transport request, then choose Finish.

    Image depicting step-4c-class-transport-request

The class is displayed in a new editor.

Image depicting step-4d-class-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: Create HTTP client
View Full Instructions

To be able to access the external service, you must maintain a cloud destination for the foreign system and create an HTTP client. Proceed as follows:

  1. Add the method implementation below and wrap it in an exception.

  2. 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
  1. Check your syntax (Ctrl+F2).
  2. 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
View Full Instructions

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

  1. 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
  1. Check your syntax (Ctrl+F2).
  2. Save (Ctrl+S) and activate (Ctrl+F3) your class.
  3. Run your class in the console (F9).

The output should now look something like this:
Image depicting step10-output-2

Done
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Step 10: Test yourself
Which of the following is code snippets is correct? Choose all that apply.
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