java - sorting by code -

i have food categories in db like:

 category_id | parent_id |  code  |               name                -------------+-----------+--------+----------------------------------            1 |           |        | root            2 |         1 | 1      | vegetables           11 |         1 | 10     | seeds           54 |        11 | 10.1   | sunflower seeds           12 |         1 | 11     | sugar , candy           22 |         2 | 1.1    | frozen vegetables 

i want sort either code in query or programmatically using parent_id (in pojo after mapping). effect should this:

1 ---1.1 ------1.1.1 ------1.1.2 ------1.1.3 ---1.2 2 3 ---3.1 ... 

i tried order code received records ordered like: 1, 10.1.1, 11, 1.1.1 should try sort in query or when it's mapped. maybe there interfaces/other utils in java purpose?

code type character varying , i'm using postgresql

something this. sorts parent_id because sorting on varchar column code column not easy due mismatch between character ordering , numeric ordering.

with recursive cat_tree (    select category_id, parent_id, name, array[category_id] sort, category_id::text path    category    parent_id null    union    select c.category_id, c.parent_id, c.name, p.sort||c.category_id, p.path||'.'||c.category_id    category c      join cat_tree p on p.category_id = c.parent_id ) select category_id, parent_id, path, name cat_tree order sort; 

sqlfiddle: http://sqlfiddle.com/#!12/fab3c/1