HTTP Call to Google Geocode

Question

Hi,
I'm trying to make an HTTP call to the Google geocode service in an 6.20 client.
The URL for the call is http://maps.googleapis.com/maps/api/geocode/xml?address=1,STREET,CITY,POSTCODE,&client=gme-ourclient&sensor=false&signature=fancygooglesignature=
(I've change the client and the signature to rubbish for the example)
I've put this URL (with the correct client and signature) in a web browser or a SAP html viewer it works fine and returns the required geocode.
However, If I run it as a HTTP client call in a program it fails as google doesn't understand the client/signature pairing. The signature is getting changed somewhere in the call.
My code is
* Creation of new IF_HTTP_Client object
  CALL METHOD cl_http_client=>create_by_url
    EXPORTING
      url                = l_http_url
    IMPORTING
      client             = l_http_client
    EXCEPTIONS
      argument_not_found = 1
      plugin_not_active  = 2
      internal_error     = 3
      OTHERS             = 4.
* Check this was successful
  CHECK : sy-subrc IS INITIAL.
* Set the request method
  l_http_client->request->set_header_field( name  = '~request_method'
                                            value = 'GET' ).
* Set the header
  l_http_client->request->set_header_field( name  = 'Content-Type'
                                            value = 'text/xml; charset=utf-8' ).
* Send the request
  l_http_client->send( ).
* Reterive the result
  CALL METHOD l_http_client->receive
    EXCEPTIONS
      http_communication_failure = 1
      http_invalid_state         = 2
      http_processing_failed     = 3
      OTHERS                     = 4.
content = l_http_client->response->get_cdata( ).
I've tried turing of encoding and compression, passing the parameters individually into the object but nothing works.
However, if I try the public geocode URL ( http://maps.google.com/maps/api/geocode/xml?address=1,STREET,CITY,POSTCODE,&sensor=false) it works fine.
Any ideas how to use the URL with the signature?

Answer 1

This is an example that works like our current solution:
DATA: lr_conv TYPE REF TO cl_abap_conv_in_ce,
plaintext TYPE string.
DATA: lv_sign_key_x TYPE xstring,
lv_sign_key   TYPE string,
lv_hmac_result TYPE string,
lv_sign_string TYPE string.
TYPE-POOLS: abap.
lv_sign_string = url.
lv_sign_key = 'your_sign_key'.
* String to SafeBase64
REPLACE ALL OCCURRENCES OF '_' IN lv_sign_key WITH '/'.
REPLACE ALL OCCURRENCES OF '-' IN lv_sign_key WITH '+'.
* Do not sign the protocol/domain
REPLACE 'http://maps.googleapis.com' IN lv_sign_string WITH ''.
*Convert key from String to xString (hex)
CALL FUNCTION 'SSFC_BASE64_DECODE'
EXPORTING
b64data = lv_sign_key
IMPORTING
bindata = lv_sign_key_x.
* Generate signature
cl_abap_hmac=>calculate_hmac_for_char(
EXPORTING
if_algorithm     = 'SHA1'
if_key           = lv_sign_key_x
if_data          = lv_sign_string
IMPORTING
ef_hmacb64string = lv_hmac_result
* SafeBase64 -> Base64 again
REPLACE ALL OCCURRENCES OF '/' IN lv_hmac_result WITH '_'.
REPLACE ALL OCCURRENCES OF '+' IN lv_hmac_result WITH '-'.
* Concatenate final URL
CONCATENATE url '&signature=' lv_hmac_result INTO url.
Best regards,
Hendrik Behrens