Keep a Java object alive for the duration of a session

Question

In my JSP application, I want to keep track of the user that's logged in.

When the user tries to log in, I use database transactions in a UserManager class to verify that the entry exists (I'm not aiming to make a very secure site, most of this is for learning).

That UserManager class constructs a User instance object out of the retrieved information on the user (i.e. their name, age, photo, etc).

I use this object to efficiently call prepare the presentation on the user's home page, after the log in is successful.

The trouble is, I don't know how to keep this User object alive for the duration of the whole session with the user. For example, if he goes to other pages, I still want to be able to call

user.getPhoto()

or

user.getLastName()

without complicated database queries each time.

Is there any way to do this?

Are you using any framework or only servlets ? – Dici Sep 04 '14 at 16:28 — Dici, Sep 04 '14 at 16:28
No framework. Just Servlets – CodyBugstein Sep 04 '14 at 16:45 — CodyBugstein, Sep 04 '14 at 16:45

score 4 · Accepted Answer · edited May 23 '17 at 11:45

Store the object in session. Inside your servlet, just call this:

User user = ... //use your UserManager or something else to get the user
if (<valid user>) {
    //store the user object in session
    request.getSession().setAttribute("user", user);
}
//forward to the next view...

Then you can retrieve the data in your view (JSP, Facelets) using Expression Language:

<!DOCTYPE html>
<html lang="en">
    <!-- tags... -->
    <div>
        Welcome ${user.name}
        <!-- ${user.name} will call session.getAttribute("user").getName() for you -->
    </div>
</html>

More info:

Didn't provide an example using scriptlets because you should not use them. Explanation on link above.

Don't forget to clear the session when performing a log out:

request.getSession().invalidate();

Keep a Java object alive for the duration of a session

1 Answers1