apex_web_service.make_rest_request POST has bad json or returns ORA-06502 numeric or value error - json

Question

I cannot get successful POST /authentication/login with E-verify/DHS using PLSQL using apex_web_service.make_rest_request(). I tried in Apex first but got numeric/value error and swtiched to PLSQL to debug. It uses json. Apex version is 4.2. I can get a GET to work, but that does not use headers or parms.
If specify p_parm_name using string_to_table() or using p_parm_name by specifying each array value separately, then I get {"status":400,"error":"There was a problem in the JSON you submitted: ActionDispatch::Http::Parameters::ParseError"}
If I specify p_body then i get an ORA-06502: PL/SQL: numeric or value error.
If I specify p_body but use wrong password, I get (what I think is) non-ascii response like the following:
If I use varchar2 instead of clob in various spots I get same errors
If I use postman with the same p_body then it works!!
So of course I'd love for this code to work, but in lieu of that, HOW DO I SEE THE REQUEST coming from Oracle/Apex so I can confirm what the json looks like (for #1 above)? Thanks!
Here is code.
l_parm_names apex_application_global.vc_arr2;
l_parm_values apex_application_global.vc_arr2;
l_resp_clob clob;
l_resp_length integer;
l_body_varchar2 varchar2(4000);
l_body_clob clob;
begin
l_parm_names(1) := 'username';
l_parm_values(1) := 'user1234';
l_parm_names(2) := 'password';
l_parm_values(2) := 'pass1234';
l_body_varchar2 := '{"username":"user1234","password":"pass1234"}';
l_body_clob := to_clob(l_body_varchar2);
apex_web_service.g_request_headers.delete();
apex_web_service.g_request_headers(1).name := 'Content-Type';
apex_web_service.g_request_headers(1).value := 'application/json';
l_resp_clob := apex_web_service.make_rest_request(
p_url => 'https://stage-everify*******login',
p_http_method => 'POST',
-- p_parm_name => apex_util.string_to_table('username:password'),
-- p_parm_value => apex_util.string_to_table('user1234:pass1234')
-- p_parm_name => l_parm_names,
-- p_parm_value => l_parm_values
p_body => l_body_clob
);
INSERT INTO ev_clob (body, resp, dte, note)
VALUES (l_body_clob, l_resp_clob, SYSDATE, 'Stack Script 1'); commit;
end;

Answer 1

You need to generate the json in this way
SET SERVEROUTPUT ON
DECLARE
l_cursor SYS_REFCURSOR;
BEGIN
OPEN l_cursor FOR
SELECT e.empno AS "employee_number",
e.ename AS "employee_name",
e.deptno AS "department_number"
FROM emp e
WHERE rownum <= 2;
APEX_JSON.initialize_clob_output;
APEX_JSON.open_object;
APEX_JSON.write('employees', l_cursor);
APEX_JSON.close_object;
DBMS_OUTPUT.put_line(APEX_JSON.get_clob_output);
APEX_JSON.free_output;
END;
/
Here you can find more information
https://docs.oracle.com/cd/E59726_01/doc.50/e39149/apex_json.htm#AEAPI29737
BEGIN
apex_json.open_object; -- {
apex_json.open_object('obj'); -- "obj": {
apex_json.write('obj-attr', 'value'); -- "obj-attr": "value"
apex_json.close_all; -- }}
END;