How to avoid the same user logging several times at the same time?

Hi, I like to avoid to users can run the application in a moment. A user can only have one application running in a moment. Now i manage the session using jsessionid and expire session. 10 There are a better form to avoid these behavior? Do you now a tutorial or article that explain this to

Re: How to display a warning message.

j2se is not j2ee... look at java.sun.com for more information... I know, i´m really newbie in server side, I dont know how to display a popup dialog from an Action. probably is not a good idea ? Maybe this is not the correct mailing list for this newbie question. Someone can tell me a good newb

How to display a warning message.

hi, I try to display a message in a jsp page. Is correct to use a JOptionPane? There are other options to show a message from the Action class ? 1 The user fill a form. 2 an action look in the database 3 if i have a empty result i show a warning message. /* check the list */ final ModelForm fo