web application session cache

Question

I want to cache data for a user session in a web application built on struts.What is the best way to do it .Currently we store certain information from the DB in java objects in the user's session .Works fine till now but people are now concerned about memory usage etc. Any thought on how best to get around this problem.

Answer 1

It's usually bad practice to store whole objects in the user session for this reason. You should probably store just the keys in the session and re-query the database when you need them again. This is trade-off, but usually acceptable for most use-cases. Querying the database on keys is usually acceptable to do between requests, rather than storing objects in session.

If you must have them in session, consider using something like an LRUMap (in Apache Collections).

Answer 2

Works fine till now but people are now concerned about memory usage etc.

Being "concerned" is relatively meaningless - do they have any concrete reason for it? Statistics that show how much memory session objects are taking up? Along the same line: do you have concrete reasons for wanting to cache the data in the user session? Have you profiled the app and determined that fetching this data from the DB for each request is slowing down your app significantly?

Don't guess. Measure.