I have heard many things about REST, oauth, JSON and all these things. Finally i have to meet these terms this week. There was a third party tool which is provding a REST service and i have to consume it with ABAP. Interestingly i learnt that there is not any Enterprise Service infrastructure in order to call REST services. Therefore i had to use HTTP service objects within ABAP program library. cl_http_client is the main class for REST services. Calling a REST service is consist of two parts. In this post i will focust on the first part. It is getting access token which is required to successfully make main webservice and this is the second poart of REST service.
There are a few different authentication method to get access token. I have used password as grant type. Below i am sharing my custom functiom module code which i have used to acquire an access token for my REST service. Z_GET_ACCESS_TOKEN function returns the access token acquired from the provider service and gives an exception if the service does not return an 200 (successfull http call).
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function z_get_access_token. *"---------------------------------------------------------------------- *"*"Local Interface: *" EXPORTING *" REFERENCE(E_ACCESS_TOKEN) TYPE LOCALFILE *" EXCEPTIONS *" ERROR *"---------------------------------------------------------------------- data: lo_http_client type ref to if_http_client . data: lv_http_error_descr type string, lv_http_error_descr_long type xstring. data: lv_http_return_code type i. data: lv_access_token_str_found type boole_d, lv_expire_str_found type boole_d. data: lv_url type string, lv_xml_result_str type string. data: lv_cdata type string. data: lv_content_length_value type i. data: lv_strlen type i. data lv_client_id type localfile. data lv_client_secret type localfile. data lv_username type localfile. data lv_password type localfile. data lv_access_token type localfile. data lv_token_expire_seconds type char10. types: begin of ty_result, str(200), end of ty_result. data: lt_itab_result type table of ty_result with header line. *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * Create the lo_http_client using URL : lv_url = 'http://{provider_server}/{provider_service}/oauth/token'. lv_client_id = '{client_id}'. lv_client_secret = '{client_secret}'. lv_username = '{username}'. lv_password = '{pasword}'. ** Create the HTTP client call method cl_http_client=>create_by_url exporting url = lv_url importing client = lo_http_client exceptions argument_not_found = 1 plugin_not_active = 2 internal_error = 3 others = 4. * Set up the HTTP Post call method lo_http_client->request->set_method exporting method = 'POST'. call method lo_http_client->request->set_version exporting version = if_http_request=>co_protocol_version_1_0. " 1.0 lo_http_client->request->set_header_field( name = 'Content-Type' value = 'application/x-www-form-urlencoded' ). *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * Body of POST Request (SET_CDATA) and Content Length: concatenate 'grant_type=password' '&' 'client_id=' lv_client_id '&' 'client_secret=' lv_client_secret '&' 'username=' lv_username '&' 'password=' lv_password into lv_cdata. lv_content_length_value = strlen( lv_cdata ). call method lo_http_client->request->if_http_entity~set_cdata exporting data = lv_cdata length = lv_content_length_value offset = 0. * Send the HTTP Post call method lo_http_client->send exporting timeout = 15 " 15 Seconds exceptions http_communication_failure = 1 http_invalid_state = 2. * Disable SAP's pop-up for user id and password: lo_http_client->propertytype_logon_popup = lo_http_client->co_disabled. " POPUP for user id and pwd *Read the Response call method lo_http_client->receive exceptions http_communication_failure = 1 http_invalid_state = 2 http_processing_failed = 3. * Get the HTTP return code from the HTTP POST: lo_http_client->response->get_status( importing code = lv_http_return_code ). lo_http_client->response->get_status( importing reason = lv_http_error_descr ). lv_http_error_descr_long = lo_http_client->response->get_raw_message( ). * Write the HTTP Return Code / Description to the screen: write:/ 'HTTP return Code/Description:', lv_http_return_code no-gap, '/' no-gap, lv_http_error_descr. skip 1. write:/ 'HTTP return Code/Long Description:', lv_http_return_code no-gap, '/' no-gap, lv_http_error_descr_long. skip 1. * Refresh the Request after each POST: call method lo_http_client->refresh_request( exceptions http_action_failed = 1 others = 2 ). *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * Write the data received back from the POST to the screen: clear lv_xml_result_str. lv_xml_result_str = lo_http_client->response->get_cdata( ). split lv_xml_result_str at '"' into table lt_itab_result. clear: lv_access_token_str_found, lv_expire_str_found. loop at lt_itab_result. case lt_itab_result-str. when 'access_token'. lv_access_token_str_found = abap_true. when 'expires_in'. lv_expire_str_found = abap_true. when others. if lv_access_token_str_found eq abap_true and lv_access_token is initial. lv_strlen = strlen( lt_itab_result-str ). if lv_strlen > 30. lv_access_token = lt_itab_result-str. endif. endif. if lv_expire_str_found eq abap_true and lv_token_expire_seconds is initial and lt_itab_result-str cs '0'. replace ':' with space into lt_itab_result-str. replace '#' with space into lt_itab_result-str. replace '}' with space into lt_itab_result-str. shift lt_itab_result-str by 1 places right circular. while lt_itab_result-str(1) eq space. shift lt_itab_result-str by 1 places right circular. endwhile. lt_itab_result-str(1) = ' '. shift lt_itab_result-str left deleting leading space. lv_token_expire_seconds = lt_itab_result-str. endif. endcase. endloop. if lv_http_return_code eq 200. " ok * Close the HTTP connection: lo_http_client->close( ). e_access_token = lv_access_token . else. raise error . endif. endfunction. |