PL/SQL: UTL_HTTP POST with UTF8 string results in broken characters

Question

I want to send an UTF8 json string via utl_http to a node.js Server via POST. Sending the string

["Sant Julià de Lòria"]

does arrive as

["Sant Juli� de L�ria"]

The PL/SQL code goes like:

FUNCTION http_post_varchar(
    p_url          VARCHAR2,
    p_request_body VARCHAR2 )
  RETURN VARCHAR2
AS
  req   UTL_HTTP.REQ;
  resp  UTL_HTTP.RESP;
  value VARCHAR2(32767);  -- URL to post to
  v_url VARCHAR2(200) := p_url;
  -- Post Parameters
  v_param VARCHAR2(32767) := p_request_body;
  v_param_length NUMBER := length(v_param);
BEGIN
  req := UTL_HTTP.BEGIN_REQUEST (url=> v_url, method => 'POST');
  UTL_HTTP.SET_HEADER (r      =>  req,
                       name   =>  'Content-Type',
                       value  =>  'application/json;charset=UTF-8');
  UTL_HTTP.SET_HEADER (r      =>   req,
                       name   =>   'Content-Length',
                       value  =>   v_param_length);
  UTL_HTTP.WRITE_TEXT (r      =>   req,
                       data   =>   v_param);

  resp := UTL_HTTP.GET_RESPONSE(req);
  LOOP
    UTL_HTTP.READ_LINE(resp, value, TRUE);    
  END LOOP;
  UTL_HTTP.END_RESPONSE(resp);
  RETURN 'OK';
EXCEPTION
  WHEN UTL_HTTP.END_OF_BODY THEN
    UTL_HTTP.END_RESPONSE(resp);
  RETURN 'OK';
END http_post_varchar;

Answer 1

You should change your code to:

UTL_HTTP.SET_BODY_CHARSET('UTF-8');
UTL_HTTP.SET_HEADER (r      =>   req,
                     name   =>   'Content-Length',
                     value  =>    LENGTHB(v_param));

UTL_HTTP.WRITE_RAW (r    => req,
                    data => UTL_RAW.CAST_TO_RAW(v_param));

LENGTHB for byte length because of UTF-8. Otherwise the calculated length will be false and you get an error on the target side (unexpected end of input or something).

Answer 2

Same goes for the response body e.g. when you're getting a response from a web service:

UTL_HTTP.SET_BODY_CHARSET(r=> resp, charset=>'UTF-8');

Place this call directly after Get_response.