ABAP HTTP Client: Calling REST APIs

Category
ABAP-Statements
Published
Author
Johannes

HTTP Clients enable communication with external REST APIs from ABAP. There are two main classes: CL_HTTP_CLIENT (classic) and CL_WEB_HTTP_CLIENT (modern/Cloud).

Overview

ClassAvailabilityRecommendation
CL_HTTP_CLIENTClassic ABAPOn-Premise
CL_WEB_HTTP_CLIENTABAP Cloud, from 7.54Cloud, new developments

CL_HTTP_CLIENT (Classic)

1. Simple GET Request

DATA: lo_client   TYPE REF TO if_http_client,
      lv_response TYPE string,
      lv_code     TYPE i.


" Create client
cl_http_client=>create_by_url(
  EXPORTING
    url    = 'https://api.example.com/users'
  IMPORTING
    client = lo_client
).


" Send request
lo_client->send( ).
lo_client->receive( ).


" Read response
lv_code = lo_client->response->get_status( )-code.
lv_response = lo_client->response->get_cdata( ).


" Close connection
lo_client->close( ).


IF lv_code = 200.
  WRITE: / 'Success:', lv_response.
ELSE.
  WRITE: / 'Error:', lv_code.
ENDIF.

2. GET with Query Parameters

DATA: lo_client TYPE REF TO if_http_client,
      lv_url    TYPE string.


" URL with parameters
lv_url = 'https://api.example.com/users?status=active&limit=10'.


cl_http_client=>create_by_url(
  EXPORTING url    = lv_url
  IMPORTING client = lo_client
).


" Or set parameters individually
lo_client->request->set_form_field(
  name  = 'status'
  value = 'active'
).


lo_client->send( ).
lo_client->receive( ).


DATA(lv_response) = lo_client->response->get_cdata( ).
lo_client->close( ).

3. POST Request with JSON

DATA: lo_client TYPE REF TO if_http_client,
      lv_json   TYPE string.


" Create JSON body
lv_json = '{"name":"Max","email":"[email protected]"}'.


cl_http_client=>create_by_url(
  EXPORTING url    = 'https://api.example.com/users'
  IMPORTING client = lo_client
).


" Set HTTP method
lo_client->request->set_method( if_http_request=>co_request_method_post ).


" Set Content-Type
lo_client->request->set_header_field(
  name  = 'Content-Type'
  value = 'application/json'
).


" Set body
lo_client->request->set_cdata( lv_json ).


" Send
lo_client->send( ).
lo_client->receive( ).


DATA(lv_status) = lo_client->response->get_status( )-code.
DATA(lv_response) = lo_client->response->get_cdata( ).


lo_client->close( ).


CASE lv_status.
  WHEN 200 OR 201.
    WRITE: / 'Successfully created'.
  WHEN 400.
    WRITE: / 'Invalid request'.
  WHEN 401.
    WRITE: / 'Not authorized'.
  WHEN OTHERS.
    WRITE: / 'Error:', lv_status.
ENDCASE.

4. PUT Request (Update)

lv_json = '{"name":"Max Mustermann","email":"[email protected]"}'.


cl_http_client=>create_by_url(
  EXPORTING url    = 'https://api.example.com/users/123'
  IMPORTING client = lo_client
).


lo_client->request->set_method( if_http_request=>co_request_method_put ).
lo_client->request->set_header_field(
  name  = 'Content-Type'
  value = 'application/json'
).
lo_client->request->set_cdata( lv_json ).


lo_client->send( ).
lo_client->receive( ).
lo_client->close( ).

5. DELETE Request

cl_http_client=>create_by_url(
  EXPORTING url    = 'https://api.example.com/users/123'
  IMPORTING client = lo_client
).


lo_client->request->set_method( if_http_request=>co_request_method_delete ).


lo_client->send( ).
lo_client->receive( ).


DATA(lv_status) = lo_client->response->get_status( )-code.
lo_client->close( ).


IF lv_status = 204 OR lv_status = 200.
  WRITE: / 'Successfully deleted'.
ENDIF.

6. Basic Authentication

cl_http_client=>create_by_url(
  EXPORTING url    = 'https://api.example.com/secure'
  IMPORTING client = lo_client
).


" Set Basic Auth
lo_client->authenticate(
  username = 'myuser'
  password = 'mypassword'
).


lo_client->send( ).
lo_client->receive( ).
lo_client->close( ).

7. Bearer Token (OAuth)

DATA: lv_token TYPE string VALUE 'eyJhbGciOiJIUzI1NiIs...'.


cl_http_client=>create_by_url(
  EXPORTING url    = 'https://api.example.com/protected'
  IMPORTING client = lo_client
).


" Set Authorization Header
lo_client->request->set_header_field(
  name  = 'Authorization'
  value = |Bearer { lv_token }|
).


lo_client->send( ).
lo_client->receive( ).
lo_client->close( ).

8. Custom Headers

lo_client->request->set_header_field(
  name  = 'X-API-Key'
  value = 'my-api-key-12345'
).


lo_client->request->set_header_field(
  name  = 'Accept'
  value = 'application/json'
).


lo_client->request->set_header_field(
  name  = 'Accept-Language'
  value = 'en-US'
).

9. Set Timeout

cl_http_client=>create_by_url(
  EXPORTING url    = 'https://api.example.com/slow'
  IMPORTING client = lo_client
).


" Timeout in seconds
lo_client->send( timeout = 30 ).
lo_client->receive( timeout = 30 ).

10. SSL/HTTPS Certificates

" For self-signed certificates
lo_client->propertytype_accept_cookie = if_http_client=>co_enabled.


" SSL client certificate (STRUST)
lo_client->set_ssl_id( 'ANONYM' ).  " Or PSE name


" Ignore SSL errors (FOR TESTING ONLY!)
lo_client->propertytype_logon_popup = if_http_client=>co_disabled.

CL_WEB_HTTP_CLIENT (Modern/Cloud)

11. GET Request (Cloud)

DATA: lo_client   TYPE REF TO if_web_http_client,
      lo_response TYPE REF TO if_web_http_response.


TRY.
    " Destination from SM59 or HTTP URL
    DATA(lo_destination) = cl_http_destination_provider=>create_by_url(
      i_url = 'https://api.example.com/users'
    ).


    lo_client = cl_web_http_client_manager=>create_by_http_destination(
      i_destination = lo_destination
    ).


    lo_response = lo_client->execute( if_web_http_client=>get ).


    DATA(lv_status) = lo_response->get_status( )-code.
    DATA(lv_body) = lo_response->get_text( ).


    lo_client->close( ).


  CATCH cx_web_http_client_error INTO DATA(lx_error).
    WRITE: / 'HTTP Error:', lx_error->get_text( ).
  CATCH cx_http_dest_provider_error INTO DATA(lx_dest).
    WRITE: / 'Destination Error:', lx_dest->get_text( ).
ENDTRY.

12. POST Request (Cloud)

TRY.
    DATA(lo_destination) = cl_http_destination_provider=>create_by_url(
      i_url = 'https://api.example.com/users'
    ).


    DATA(lo_client) = cl_web_http_client_manager=>create_by_http_destination(
      i_destination = lo_destination
    ).


    DATA(lo_request) = lo_client->get_http_request( ).


    " Set headers
    lo_request->set_header_field(
      i_name  = 'Content-Type'
      i_value = 'application/json'
    ).


    " Set body
    lo_request->set_text( '{"name":"Max","email":"[email protected]"}' ).


    " Execute POST
    DATA(lo_response) = lo_client->execute( if_web_http_client=>post ).


    DATA(lv_status) = lo_response->get_status( )-code.
    DATA(lv_body) = lo_response->get_text( ).


    lo_client->close( ).


  CATCH cx_web_http_client_error cx_http_dest_provider_error INTO DATA(lx_error).
    WRITE: / lx_error->get_text( ).
ENDTRY.

13. Using Destination from SM59

TRY.
    " Use destination from SM59
    DATA(lo_destination) = cl_http_destination_provider=>create_by_comm_arrangement(
      comm_scenario  = 'Z_MY_SCENARIO'
      service_id     = 'Z_MY_SERVICE'
    ).


    " Or directly by name
    DATA(lo_dest_by_name) = cl_http_destination_provider=>create_by_cloud_destination(
      i_name = 'MY_DESTINATION'
    ).


    DATA(lo_client) = cl_web_http_client_manager=>create_by_http_destination(
      i_destination = lo_destination
    ).


    " ...


  CATCH cx_http_dest_provider_error INTO DATA(lx_error).
    WRITE: / lx_error->get_text( ).
ENDTRY.

Practical Examples

14. Complete REST Client

CLASS zcl_api_client DEFINITION PUBLIC.
  PUBLIC SECTION.
    TYPES: BEGIN OF ty_user,
             id    TYPE i,
             name  TYPE string,
             email TYPE string,
           END OF ty_user,
           ty_users TYPE TABLE OF ty_user WITH EMPTY KEY.


    METHODS: constructor
               IMPORTING iv_base_url TYPE string
                         iv_api_key  TYPE string OPTIONAL.


    METHODS: get_users
               RETURNING VALUE(rt_users) TYPE ty_users
               RAISING   cx_web_http_client_error.


    METHODS: create_user
               IMPORTING is_user        TYPE ty_user
               RETURNING VALUE(rs_user) TYPE ty_user
               RAISING   cx_web_http_client_error.


  PRIVATE SECTION.
    DATA: mv_base_url TYPE string,
          mv_api_key  TYPE string.


    METHODS: create_client
               RETURNING VALUE(ro_client) TYPE REF TO if_http_client.
ENDCLASS.


CLASS zcl_api_client IMPLEMENTATION.
  METHOD constructor.
    mv_base_url = iv_base_url.
    mv_api_key = iv_api_key.
  ENDMETHOD.


  METHOD create_client.
    cl_http_client=>create_by_url(
      EXPORTING url    = mv_base_url
      IMPORTING client = ro_client
    ).


    IF mv_api_key IS NOT INITIAL.
      ro_client->request->set_header_field(
        name  = 'X-API-Key'
        value = mv_api_key
      ).
    ENDIF.


    ro_client->request->set_header_field(
      name  = 'Accept'
      value = 'application/json'
    ).
  ENDMETHOD.


  METHOD get_users.
    DATA(lo_client) = create_client( ).


    lo_client->request->set_uri_path( '/users' ).
    lo_client->send( ).
    lo_client->receive( ).


    DATA(lv_response) = lo_client->response->get_cdata( ).
    lo_client->close( ).


    " Parse JSON
    /ui2/cl_json=>deserialize(
      EXPORTING json = lv_response
      CHANGING  data = rt_users
    ).
  ENDMETHOD.


  METHOD create_user.
    DATA(lo_client) = create_client( ).


    lo_client->request->set_uri_path( '/users' ).
    lo_client->request->set_method( if_http_request=>co_request_method_post ).
    lo_client->request->set_header_field(
      name  = 'Content-Type'
      value = 'application/json'
    ).


    DATA(lv_json) = /ui2/cl_json=>serialize( data = is_user ).
    lo_client->request->set_cdata( lv_json ).


    lo_client->send( ).
    lo_client->receive( ).


    DATA(lv_response) = lo_client->response->get_cdata( ).
    lo_client->close( ).


    /ui2/cl_json=>deserialize(
      EXPORTING json = lv_response
      CHANGING  data = rs_user
    ).
  ENDMETHOD.
ENDCLASS.




" Usage
DATA(lo_api) = NEW zcl_api_client(
  iv_base_url = 'https://api.example.com'
  iv_api_key  = 'my-key'
).


TRY.
    DATA(lt_users) = lo_api->get_users( ).


    DATA(ls_new_user) = lo_api->create_user(
      is_user = VALUE #( name = 'Test' email = '[email protected]' )
    ).


  CATCH cx_web_http_client_error INTO DATA(lx_error).
    WRITE: / lx_error->get_text( ).
ENDTRY.

15. Error Handling

TRY.
    cl_http_client=>create_by_url(
      EXPORTING url    = 'https://api.example.com'
      IMPORTING client = lo_client
    ).


    lo_client->send( ).
    lo_client->receive( ).


    DATA(lv_status) = lo_client->response->get_status( ).


    CASE lv_status-code.
      WHEN 200.
        " Success
        DATA(lv_data) = lo_client->response->get_cdata( ).


      WHEN 400.
        " Bad Request
        DATA(lv_error) = lo_client->response->get_cdata( ).
        WRITE: / 'Invalid request:', lv_error.


      WHEN 401.
        WRITE: / 'Authentication failed'.


      WHEN 403.
        WRITE: / 'Access denied'.


      WHEN 404.
        WRITE: / 'Resource not found'.


      WHEN 500.
        WRITE: / 'Server error'.


      WHEN OTHERS.
        WRITE: / 'HTTP Status:', lv_status-code, lv_status-reason.
    ENDCASE.


  CATCH cx_root INTO DATA(lx_error).
    WRITE: / 'Error:', lx_error->get_text( ).


  CLEANUP.
    IF lo_client IS BOUND.
      lo_client->close( ).
    ENDIF.
ENDTRY.

16. Sending Binary Data (Files)

DATA: lv_file_content TYPE xstring.


" File as binary data
lv_file_content = '...'.  " e.g. from file or table


lo_client->request->set_method( if_http_request=>co_request_method_post ).
lo_client->request->set_header_field(
  name  = 'Content-Type'
  value = 'application/octet-stream'
).


lo_client->request->set_data( lv_file_content ).


lo_client->send( ).
lo_client->receive( ).

17. Multipart/Form-Data

DATA: lv_boundary TYPE string VALUE '----WebKitFormBoundary7MA4YWxk'.


lo_client->request->set_header_field(
  name  = 'Content-Type'
  value = |multipart/form-data; boundary={ lv_boundary }|
).


DATA(lv_body) = |--{ lv_boundary }\r\n| &&
                |Content-Disposition: form-data; name="field1"\r\n\r\n| &&
                |value1\r\n| &&
                |--{ lv_boundary }\r\n| &&
                |Content-Disposition: form-data; name="file"; filename="test.txt"\r\n| &&
                |Content-Type: text/plain\r\n\r\n| &&
                |File content here\r\n| &&
                |--{ lv_boundary }--\r\n|.


lo_client->request->set_cdata( lv_body ).

Important Notes / Best Practices

  • Use CL_WEB_HTTP_CLIENT for ABAP Cloud and new developments.
  • Always call close() - even on errors (TRY-FINALLY).
  • Use Destinations (SM59) for configurable endpoints.
  • Set Timeouts for slow external APIs.
  • Import SSL certificates in STRUST for HTTPS.
  • Use /ui2/cl_json to serialize/deserialize JSON.
  • Evaluate HTTP status codes for error handling.
  • Don’t hardcode API keys/tokens in code - use destinations.
  • Implement logging for debugging.
  • Consider proxy settings in production systems.