Java Security

If you have a rest api with ORDS, it can accept a json payload and it can be stored natively as a json document in the database, or as rows in a table. There are multiple code/feature paths you can take to accomplish this.
ORDS is responsible for serving up the REST APIs, not for CALLING APIs. To call a REST API from the database, you'd use an apex helper package or write your own UTL.HTP calls.

Call Rest API from oracle and convert the json content into oracle table data fields and store in the database - is it possible solution? if so , how?

-- Original rest http://openexchangerates.org/api/currencies.json:
-- {
--  "AED": "United Arab Emirates Dirham",
--  "AFN": "Afghan Afghani",
--  "ALL": "Albanian Lek",
--  "AMD": "Armenian Dram",
--  "ANG": "Netherlands Antillean Guilder",
-- ...
with function json_transpose(jsn clob) return clob as
-- {key1:value1,...} -> [{name:key1,value:value1},...]
  ctx dbms_mle.context_handle_t;
  res clob := empty_clob()||'';
begin
  ctx := dbms_mle.create_context();
  dbms_mle.export_to_mle(ctx, 'jsn', jsn);
  dbms_mle.eval(ctx, 'JAVASCRIPT', q'<
    const bind = require("mle-js-bindings");
    const lob = bind.importValue("jsn");
    const src = JSON.parse(lob.read(lob.length(),1));
    const tgt = [];
    for(const elm in src) tgt.push({name:elm,value:src[elm]});
    tgt
    >', res);
  dbms_mle.drop_context(ctx);
  return res;
end;
rest as (select json_transpose(httpuritype('http://openexchangerates.org/api/currencies.json').getclob()) j from dual)
select *
from rest
     nested j[*] columns(name, value)
where rownum<=5;
/

NAME  VALUE                                   
----- ----------------------------------------
AED   United Arab Emirates Dirham             
AFN   Afghan Afghani                          
ALL   Albanian Lek                            
AMD   Armenian Dram                           
ANG   Netherlands Antillean Guilder           

Thanks Jeff, Yes I need to call the Rest API by GET , can you send me links for example usiing Apex package and utl htttp

If you Google for them, you will find them in the usual places by the usual people.