Call external APIs and retrieve the data in ABAP

[suhas_gavas]

Hello All,

As the ODATA protocol is getting famous nowadays, and so many APIs avail different services/data as ODATA service, how an ABAPer can male use of it?

Here is one of the way to call an external API and get the data into ABAP system.

 

Step 1. Use class CL_HTTP_CLIENT to get an object of type IF_HTTP_Client. There are different methods for getting this object. example: by the API URL or by HTTP Destination etc.

In below code snippet I have used API URL to get the object. Once the object of type IF_HTTP_Client is received, then execute the instance methods SEND() and RECEIVE() to establish Connection and Dispatch of Data and receive HTTP Response.

 

 

REPORT zsuhas.



*HTTP Client Abstraction

DATA  lo_client TYPE REF TO if_http_client.



*Data variables for storing response in xstring and string

DATA  : lv_xstring    TYPE xstring,

        lv_string     TYPE string,

        lv_node_name  TYPE string.



CLEAR : lv_xstring, lv_string, lv_node_name.



*Put required node name into constant (case sensitive)

CONSTANTS : co_req_node TYPE string VALUE '<YOUR_REQUIRED_NODE_NAME>'.



*Creation of New IF_HTTP_Client Object

cl_http_client=>create_by_url(

EXPORTING

  url                = "URL

  proxy_host         = "Proxy

  proxy_service      = "Port

  sap_username       = "Username

  sap_client         = "Client

IMPORTING

  client             = lo_client

EXCEPTIONS

  argument_not_found = 1

  plugin_not_active  = 2

  internal_error     = 3

  ).



IF sy-subrc IS NOT INITIAL.

* Handle errors

ENDIF.



*Structure of HTTP Connection and Dispatch of Data

lo_client->send( ).

IF sy-subrc IS NOT INITIAL.

* Handle errors

ENDIF.



*Receipt of HTTP Response

lo_client->receive( ).

IF sy-subrc IS NOT INITIAL.

* Handle errors

ENDIF.

 

Note : If you might be asked to authenticate while calling RECEIVE method. If so, insert the following piece of code after you get the create object of type IF_HTTP_client.

 

lo_client->propertytype_logon_popup = lo_client->co_disabled.

  data l_username type string.

  data l_password type string.

  l_username = MY_USERNAME.

  l_password = MY_PASS.



  lo_client->authenticate(

  exporting

      proxy_authentication = 'X'

      client               = Client    " R/3 System, client number from logon

    username             = l_username    " ABAP System, User Logon Name

    password             = l_password    " Logon ID

*      language             = language    " SAP System, Current Language

    ).

 

Step 2 . Use get_data() method of the attribute response of object received in Step 1 to get the data in Binary format. And store it in a variable of type xstring.

*Return the HTTP body of this entity as binary data

lv_xstring = lo_client->response->get_data( ).



*Displays XML File

CALL METHOD cl_abap_browser=>show_xml

  EXPORTING

    xml_xstring = lv_xstring

    size        = cl_abap_browser=>large.

 

Step 3. User standard procedure for XML processing in OO ABAP. as below.

*Create the factory object

DATA(lo_ixml)               = cl_ixml=>create( ).



*Create a factory for input and output streams

DATA(lo_stream_factory)     = lo_ixml->create_stream_factory( ).



*Create input stream for data source byte string

DATA(lo_istream)            = lo_stream_factory->create_istream_xstring( string = lv_xstring ).



*Create an XML document in DOM format

DATA(lo_document)           = lo_ixml->create_document( ).



*Create a parser

 DATA(lo_parser)            = lo_ixml->create_parser(

             stream_factory = lo_stream_factory

             istream        = lo_istream

             document       = lo_document ).





DATA(lv_rc) = lo_parser->parse( ).



IF lv_rc <> ixml_mr_parser_ok.

*  ... "Error handling

  RETURN.

ENDIF.

 

Step 4.  Get the root node of your DOM structure and all its children. Use the iterator object to reach your desired node. Once the desired node is reached, create another iterator object to iterate the desired node. the constants "co_node_text", "co_node_element" and "co_node_cdata_section" help determine what kind of node type is read.

At this stage the data of the desired node is available in your ABAP system to play with. I am using write statement below to display the node element name and its corresponding value. Any operation can be performed once the data is brought into your SAP system.

 

DO.

  DATA(req_node) = lo_iterator_req->get_next( ).

  IF req_node IS INITIAL.

    EXIT.

  ENDIF.



*Returns the node type

  DATA(lv_nodetype) = req_node->get_type( ).



*Name

  IF lv_nodetype = if_ixml_node=>co_node_element. "Element

    IF req_node->get_name( ) NE co_req_node.

      WRITE : req_node->get_name( ).

      WRITE : ':'.

    ENDIF.

  ENDIF.



*Value

  IF lv_nodetype = if_ixml_node=>co_node_text OR lv_nodetype =  if_ixml_node=>co_node_cdata_section. "Literal Text/CDATA Section

    WRITE : req_node->get_value( ).

    SKIP.

  ENDIF.

ENDDO.