Preface – This post is part of the ABAP Programs series.

In this step we will call the service to get the token and store that token in a global variable for later use.

METHOD get_token.
    DATA: lo_http_client TYPE REF TO if_http_client.
    DATA: response TYPE string,
          lv_url   TYPE string.
    CONSTANTS: lv_initial_url TYPE string VALUE '<Blockchain Service Link>',
               lv_auth        TYPE string VALUE 'Basic <your login credentials>'.
    "create HTTP client by url
    CALL METHOD cl_http_client=>create_by_url
      EXPORTING
        url                = lv_initial_url
      IMPORTING
        client             = lo_http_client
      EXCEPTIONS
        argument_not_found = 1
        plugin_not_active  = 2
        internal_error     = 3
        OTHERS             = 4.
    "Available API Endpoints
    "https://blockchain-service.cfapps.sap.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    "https://blockchain-service.cfapps.eu10.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    "https://blockchain-service.cfapps.us10.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    IF sy-subrc <> 0.
      "error handling
    ENDIF.
    "setting request method
    lo_http_client->request->set_method('GET').
    "adding headers
    lo_http_client->request->set_header_field( name = 'Authorization' value = lv_auth ).
    "Available Security Schemes for productive API Endpoints
    "OAuth 2.0
    CALL METHOD lo_http_client->send
      EXCEPTIONS
        http_communication_failure = 1
        http_invalid_state         = 2
        http_processing_failed     = 3
        http_invalid_timeout       = 4
        OTHERS                     = 5.
    IF sy-subrc = 0.
      CALL METHOD lo_http_client->receive
        EXCEPTIONS
          http_communication_failure = 1
          http_invalid_state         = 2
          http_processing_failed     = 3
          OTHERS                     = 5.
    ENDIF.
    IF sy-subrc <> 0.
      "error handling
    ENDIF.
    response = lo_http_client->response->get_cdata( ).
   GV_TOKEN = response. "Global Variable
  ENDMETHOD.