how can i insert a composite component (menu of menus) in my database

Question

I am implementing the Composite Design pattern and I need to insert a menu in the database but the menu may consist of other menus and menu items so when I tried to insert them

Answer 1

menu.getParent_id() will always return null for the top-most Menu because by implication it doesn't have a parent. Since menu traversal begins with the top-most Menu you need to handle this specific case.

Firstly, you need a way to represent a Menu without a parent in your database table. For example, you may choose NULL to represent this. Then handle the case:

if(menu.getParent_id() == null) {    
    statement.setNull(3, java.sql.Types.INTEGER);
else {
    statement.setInt(3, menu.getParent_id());
}

You also need to create the menu in the database before calling the method recursively. Otherwise menu.getParent_id() will return null for every Menu and not just the top-most. So this needs to happen before creating the submenus: int res = statement.executeUpdate();