Oracle 12c version 12.1.0.2 (the latest version as of 11.11.2014) adds JSON support:
https://docs.oracle.com/database/121/NEWFT/chapter12102.htm#BGBGADCC
It’s been available since October 17th. https://blogs.oracle.com/db/entry/oracle_database_12c_release_1
If you are unable to patch/work with that version there is an excellent package written by Lewis Cunningham and Jonas Krogsboell: PL/JSON
* http://pljson.sourceforge.net/
It’s an excellent package (I have used it in numerous database installations).
The examples included are good and cover most scenarios.
declare
ret json;
begin
ret := json_dyn.executeObject('select * from tab');
ret.print;
end;
/