export_ddl.sql

SELECT dbms_metadata.get_ddl(object_type, object_name, owner) || ';' AS object_ddl
FROM DBA_OBJECTS
WHERE 
      OWNER = '<owner>'
  AND OBJECT_TYPE IN (
      'TABLE'
    , 'INDEX'
    , 'SEQUENCE'
    , 'VIEW'
  )
ORDER BY
    OWNER
  , OBJECT_TYPE
  , OBJECT_NAME
;