parameters stability in jsp page

I am working on JSP-servlet application and now I am programming a page which edit information about registrars.

The senario is that there's an ArrayList I send form servlet to JSP page when I load the page. The ArrayList contains information about groups the registrar belongs, the ArrayList is resulted after making multiple SQL statements. When user try to edit some fields and make one required field empty and submit the form, the servlet makes validation and r开发者_StackOverfloweturn error to edit page.

The problem I face is that all the groups I sent in the first time fly in the sky. So I have to make connection to DB again and make multiple queries to get the groups again and send it back to JSP page. Is there's another simple way to make arrayList stable in JSP page ?

EDIT Here's the code which I make the scope of the ArrayList in the session.

<c:set var="userGroups" value="${userGroups}" scope="session"></c:set>

Either store it in the session or just live with it. I really don't see any issues with that. If the concrete problem is that you have to copypaste the same code again or that the whole code is ugly to have in a Servlet class, then just refactor/hide that into an useable DAO class which you import/call/reuse in the Servlet the usual Java way.

Update: as per your update, this doesn't make sense. You just need to change your servlet code from

request.setAttribute("userGroups", userGroups);

to

request.getSession().setAttribute("userGroups", userGroups);

You don't need <c:set> for this.