What to store in session/request

Question

Hello.
I'd appreciate some input on a design issue that i have. I am building some new components in a system that consists of JSP pages and servlets, which is new technology to me. I will try to describe my question in a simple and straightforward way:
My JSP page has a function where i can retrieve a list of people, based on some filtering criteria. It calls a servlet, that uses underlying components to read the persons from the database and compose an ArrayList of Person objects. It then attaches this ArrayList to the Session bean using the setAttribute method on the HttpSession object.
The JSP page then lists the result list from the search for people and using a control on the page, the user can move one or more persons from the search result list to a list of selected people, creating a team of one or more persons. This team is stored in an ArrayList attached to the session object and it's retreived, updated and re-attached to the session object by the servlet every time the user clicks on the control that selects a person to be added to the team. On form submit, the JSP page stores key information about the selected person in hidden fields in the form and the servlet extracts this information from the request object and updates the ArrayList and re-stores it in the session object.
When the "save team" button is pressed (form submit) and control returns to the servlet, it extracts the selected persons from the request object and uses underlying components to save the list. In essence, the session object is used to "send" the search result and the current list of members in ther team to the JSP page. The request object is used to send the current list of persons in the team from the JSP page to the servlet.
Now to my question: what is the best practice design for a function like this one? Is using the session object to transfer the search result list from a servlet to a JSP page a good solution? Is it a good solution to keep the list of selected persons in an object attached to the session object until it is finally saved a good solution. It is not entirely clear to me when i should store data on the session object and when to use the request. Also, what mechanisms are there to transfer data from the servlet to the JSP page, other than attaching it to the session object?

Answer 1

Can the servlet attach an object to the request object and can the JSP page access it just like it can with objects attached to the session object?Yes. Just use HttpServletRequest#setAttribute() and forward the request to the JSP.
Is there a general guideline for what to store in the session and what to store in the request? Store request scoped variables (form input values, request-specific variables, etc) in request scope and session scoped variables (logged in user, user settings, user specific dropdown list contents, session-specific variables, etc) in session scope.
My picture of this was that the request is something that is generated when a form (JSP page) is submitted and that it cannot be used to transfer data from a servlet to a JSP page. Is that wrong?Yes, it is wrong.