External API Integration in SAP using REST handlers – PART 2

[former_member184739]

Hello Everyone,

In this blog we will discuss in detail about the technical objects and the ABAP code required to consume the external rest api in SAP using the standard handler classes available in your system. To know about the overview, prerequisites and about the configurations required, please visit the part 1 of this blog series. Let’s get started.

Technical implementation:

In this section, all steps are described that you must implement for calling an external SLACK based web service from ABAP. First we send a GET request to the external REST api and then receive the response data in JSON format. Afterwards this JSON is converted into native ABAP format.

Following are the ABAP classes are used.

CL_HTTP_CLIENT

CL_REST_HTTP_CLIENT

/UI2/CL_JSON

Step 1:

Create a new REST client object with necessary request headers and authorization key.

Destination details should be maintained and received from SM59.

REPORT z_fetch_slack_data.



*Declarations for REST handlers



DATA: go_http_client TYPE REF TO if_http_client,

      go_rest_client TYPE REF TO cl_rest_http_client.



*Declarations for Data refereces

DATA:lo_json TYPE REF TO /ui2/cl_json.



*Fetch the SLACK destination details from SM59 and create the HTTP client reference

CALL METHOD me>create_http_client

  EXPORTING

    i_rfc_dest = gc_rfc_dest

  IMPORTING

    e_return   = l_wa_return.

IF l_wa_return IS NOT INITIAL.

* Send the error message

  e_return = l_wa_return.

  RETURN.

ENDIF.

 

METHOD create_http_client.

*& This method is used to fetch the destination details about the SLACK Server from SM59*

*---------------------------------------------------------------------------*

* Data Declarations*

*---------------------------------------------------------------------------*

  DATA:lv_reason        TYPE string,

       lv_utc_timestamp TYPE timestampl.



  DATA gv_auth_val TYPE string.



  CONSTANTS gc_auth TYPE string VALUE 'Authorization' ##NO_TEXT.

  CONSTANTS gc_content_type TYPE string VALUE 'content-type'.

  CONSTANTS gc_accept TYPE string VALUE 'ACCEPT' ##NO_TEXT.

  CONSTANTS gc_accept_value TYPE string VALUE 'application/json'.

  CONSTANTS gc_rfc_dest TYPE rfcdest VALUE 'SLACK_REST_API_CONV' ##NO_TEXT.

  CONSTANTS gc_tabname TYPE rstable-tabname VALUE 'Z_SLACK_LOG'."Table Name

  CONSTANTS: gc_e TYPE dd26e-enqmode VALUE 'E'.



*Create the HTTP client instance

  CALL METHOD cl_http_client=>create_by_destination

    EXPORTING

      destination              = i_rfc_dest

    IMPORTING

      client                   = go_http_client

    EXCEPTIONS

      destination_not_found    = 1

      internal_error           = 2

      argument_not_found       = 3

      destination_no_authority = 4

      plugin_not_active        = 5

      OTHERS                   = 5.

  IF sy-subrc NE 0.

    "Log the Exception

*Ping Destination Failed get time stamp field

    lv_utc_timestamp.

    lv_reason = sy-msgv1.

    RETURN.

  ENDIF.



  CHECK go_http_client IS BOUND.

*Set the HTTP header fields

  CALL METHOD go_http_client->request->set_header_field

    EXPORTING

      name  = gc_auth

      value = gv_auth_val.

  CALL METHOD go_http_client->request->set_header_field

    EXPORTING

      name  = gc_accept

      value = gc_accept_value.

  CALL METHOD go_http_client->request->set_header_field

    EXPORTING

      name  = gc_content_type

      value = gc_accept_value.

  " set http protocol version

  go_http_client->request->set_version(

  if_http_request=>co_protocol_version_1_0 ) .

ENDMETHOD.

 

Step 2:

REST call – HTTP GET

We get a string variable that contains the response data in JSON format. To process the data in ABAP, it must be converted into an appropriate ABAP structure or data object for which we use standard parser class

If the request is successful, convert the JSON string into ABAP native internal table format using standard parser class /ui2/cl_json which contains methods to perform serialization and de-serialization. Please read here to know more about these operations.

Catch here is, we need to create a local type or a global type with the attribute names as same as JSON response retrieve from the REST api.

 

Continuation of Report code...

REPORT z_fetch_slack_data.



*Declations to store the native format data

TYPES: BEGIN OF ts_slack_info,

         user  TYPE string,

         email TYPE string,

       END OF ts_slack_info .



DATA ls_slack_data TYPE ts_slack_info.

DATA go_http_client TYPE REF TO if_http_client .

DATA: lr_json TYPE REF TO /ui2/cl_json.



CHECK go_http_client IS BOUND.

*Set the User ID

IF c_user_id IS NOT INITIAL.

  lv_user_guid = c_user_id-zuser_guid.

  cl_http_utility=>set_request_uri(

  EXPORTING request = go_http_client->request uri = lv_user_guid ).



*Create REST Client object

  CREATE OBJECT lo_rest_client

    EXPORTING

      io_http_client = go_http_client.

  TRY.

      lo_rest_client->if_rest_client~get( ).

      DATA(lo_response) = lo_rest_client->if_rest_client~get_response_entity( ).

      DATA(lv_http_status) = lo_response->get_header_field( '~status_code' ).

      IF lv_http_status NE 200.

        lv_error_status = lv_http_status.



*HTTP Request Failed

        DATA(lv_reason) = lo_response->get_header_field( '~status_reason' ).



*STOP Processing

        e_return-type = gc_err.

        e_return-message = lv_reason.

        RETURN.

      ENDIF.



*Receive the response data in JSON.

      DATA(lv_json_data) = lo_response->get_string_data( ).

      "Refresh the SLACK response to clear HTTP memory of previous calls

      IF go_http_client IS BOUND.

        go_http_client->refresh_response( ).

        "Close HTTP session (Exception HTTP_NO_MEMORY)

        go_http_client->close( ).

      ENDIF.



*Collect into the exception table.

    CATCH cx_rest_client_exception INTO DATA(lo_rest_client_exception).

  ENDTRY.



  IF lv_json_data IS NOT INITIAL.

    CREATE OBJECT lr_json.

    TRY .

        lr_json->deserialize_int( EXPORTING json = lv_json_data CHANGING data = ls_slack_data ).



      ENDIF.



    CATCH cx_sy_move_cast_error INTO DATA(lo_move_cast_error) .



      DATA(lv_msg_desrl_err) = `HTTP GET failed: ` && lo_move_cast_error->get_longtext( ). FREE:l_wa_reason,lo_move_cast_error.

  ENDTRY.

ENDIF.

 

Step 3: Troubleshooting

Following are some of the errors that could occur. Part 1 of this blog covers the configurations required to circumvent most of the below errors.

GET or POST method throws exception Communication Error

• Verify that the specified host name is correct.


• Check proxy server settings.
  HTTP status is 400 (Bad Request)


•  Check uri path and parameter string.

HTTP status is 401 (Unauthorized)

• Check that user name and password as specified in your program matches those of your service instance in external server.

HTTP status is 403 (Forbidden)

• Proceed as follows to check if the SSL certificate for the external server is installed correctly.

1. Call transaction SMICM.


2. Select menu item Goto → Trace File → Display End


3. If you find the following messages, re-install the SSL certificate.

Disclaimer: Above ABAP code snippets are for illustration purposes only and these are untested. Please tailor/validate these codes based on your business requirements for the production purposes.

Part 3 - We will see how to pull millions of user conversations from the Slack interface into SAP using the background report for initial loading of all data using recursive concept, delta report to pull daily changes after the initial load has completed and also we will touch base on usage of webhooks.

Stay tuned!!!

Hope you enjoyed reading the content.

Ceers

Prabha

[Former Member]

Very Informative Blog.

Keep up the good work.

Cheers!!

[noufalcheruvott]

Dear Prabharan,

 

How to set the authorisation as mentioned in the below code. how can we set the username and password for accessing the api.


call method go_http_client->request->set_header_field
 

 exporting name  = gc_auth
           

 value = gv_auth_val.


[former_member184739]

Hi Deepak.

Did you try setting the authentication as shown below.

" provide service credentials for authentification
go_http_client->authenticate( username = gc_srv_user password = gc_srv_password ).
go_http_client->propertytype_logon_popup = if_http_client=>co_disabled.

I would recommend not to hard-code the credentials like here but you can store it from the custom table with restricted authorizations to display & edit and then retrieve that values in the application code or store these details at operating system level. Please check with your BASIS team and they will be able to do this.

 

Regards

Prabha

[Jelena_Perfiljeva]

Thanks for sharing! There is no class /UI2/CL_JSON in our ECC EHP6 system, so I'm guessing it comes in with 7.4 or later version. Just for clarification you might want to note which ABAP version was used to develop the code example.

Please also use the code formatting button like in this blog, for example. There are some typos in the code too, I'd suggest to run a syntax check and pretty print on it, then copy-paste back into the blog with proper formatting. It's not clear if this code is from a report or a global class (the method that comes out of the blue is a bit confusing), this should be clarified as well.

Additionally, you might want to take a look at Clean ABAP blog for some recent code guidelines. For example, using prefixes is no longer considered a good practice. Instead, it's better to use descriptive names.

[former_member660279]

Nice

[former_member656820]

The class /UI2/CL_JSON is part of software component 'SAP_UI', not 'SAP_BASIS', if that is what you were refering to as 7.4.

I appreciate this blog from prabaharan.asokan2, also wishing he could rework the code section so that the presentation matches the importance of this topic.

[Jelena_Perfiljeva]

SAP_UI component is only available starting with Netweaver 7.4.

[former_member184739]

Hey jelena.perfiljeva , jelena.perfiljeva2 ,

Thank you for the feedback. I’ve adapted few changes which are suggested like code formatting, pretty print etc. Unfortunately I did not have the backup of entire code, I tried to do the best possible and the whole idea was to give some initial steer to the developers.

Hopefully I will do all your suggestion in my next my next write-up.

Regards,

Prabha

[former_member184739]

Hello o.does

Thank you for the inputs and heads-up. I've done the rework as much as possible. Hope this helps.

Regards

Prabha

[former_member656820]

Thanks Prabha!

[former_member259842]

Lovely pice of information.. Thanks  for sharing

[former_member682828]

Hi Prabha,

 

I ave been able to use as you explained and am able to contact the external API. But Now we have to pass the certificate in the header of the REST call. We have multiple company codes and the external system had given us certificates for each company code. they have been uploaded to STRUST. But Now when we call the API we need to pass the relevant certificate in the header for them to be able to verify the call .

 

How can we do that ? Please suggest.

Thanks!

Sandeep

[ailang]

Well Written Prabha !

[gaurav_tripathi3]

Very good Prabahakaran !

[former_member187675]

Hi Prabahakaran,

Hope you are doing well.

I am stuck in an assignment where i need to consume a REST API in sap abap. I am new to this technology. I have consumed web services but i am confused how to get the data from REST Based API using POST method.

Actually what I get is REST API, Client Credentials and other related stuff.

The service is working fine with POSTMAN application but in sap i am getting 400/Bad Request. There is no Proxy Server involved

Can you please help me in getting out of this situation?

Many Thanks,

Muhammad Asad Qureshi

[balajimeda]

Hi Muhammad,

 

Is your issue resolved?

In case you are trying to access Secured REST API for instance OAuth 2.0 protocol based REST APIs. Please follow the code from below SAP WIKI where it tries to access a Facebook API( Secured REST API ) from ABAP Program.

 

https://wiki.scn.sap.com/wiki/display/Security/Access+Facebook+using+the+OAuth+2.0+Client

 

Thanks/Balaji

 

 

 

 

[vimoralesg]

Hi prabaharan.asokan2,

I have a couple of simple questions regarding the code:

 

• The step1 and step2 are the same program, right?


• What is the reference for
  

  i_rfc_dest​

  
  


• The authorization for the API, shouldn't be part of the SM59 configuration?

 

Thanks,

Israel Morales

 

[former_member702145]

Hello prabaharan.asokan2

Do you know why the method

get_string_data

only returns the first 478 characters ?.

 

Thanks,

Javier

 

[former_member834510]

HI,

Got Error like :

 

Field "C_USER_ID" is unknown.