This describes a pattern for navigation among web pages.
Problem: when people perform an action that modifies the server-side state (such as deleting an item from a table), the action should only be performed once. Having users reload pages that result from such actions can lead to confusing error messages and invalid data.
Also, having boring pages with minimal content (such as a page consisting only of "mail sent") is annoying for the user.
You can alleviate these problems by immediately redirecting to another -- likely more interesting -- page after every such action. This should be done in the HTTP headers (via self.sendRedirect() ) so that it is transparent to the user (and doesn't break their back button).
The user still needs to receive some confirmation that the action was performed. I generally add a session variable, which is a list of messages to be displayed. At the top of every page, I check if there's anything in that session variable, and if there is I display it (usually offset by a different background color), and then clear the variable. When an action is performed, it will add any messages to that variable.
This provides a very pleasing UI, and saves a lot of tedious navigation.
Unfortunately, it would be nice if the status messages worked even when you weren't doing a redirect. However, because there's no good way to buffer the written output of a servlet, you won't know if later portions of the page are going to produce a status message when you write the top of the page. If you place status-message-producing actions in the awake method of the servlet, you won't have this problem.
-- IanBicking - 20 Nov 2001