Query to display output in json format

 SELECT JSON_OBJECT(

    'PRODUCT_CLASS' VALUE flv.lookup_code,

    'PRODUCT_CLASS_DESCRIPTION' VALUE flv.description    

     ) AS json_output

FROM

    fnd_lookup_values flv

WHERE

        flv.lookup_type = 'PRODUCT_CLASS'

    AND flv.enabled_flag = 'Y'

    AND trunc(nvl(flv.end_date_active, sysdate)) >= trunc(sysdate);