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

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.

Answer 3

Sometimes the problem is not with Unicode. You can use the conversion to ASCII code
v_param := REPLACE (ASCIISTR (v_param), '\', '\u');