Servlet side Cache implementation - need cache (updateable, portable) in Servlet

Question

Hi Guys,
          Any ideas on implementing an updateable cache on a servlet. The problem is
          that
          it must be updateable (I must be able to tell it to update itself whenever a
          welldefined
          event occurs), and it must work in a cluster environment, and I would prefer
          it to
          be J2EE portable.
          I know I can poll from the servlet - but this isn't the most elegant
          approach.
          My servlet needs to do some really fast security/auditing, but I don't want
          it to
          always do something like an EJB lookup. I can quite easily cache what I
          need
          in the hashmap - problem is updateing it and also having it work in a
          clustered
          environ.
          Any other ideas appreciated,
          Jon
          

Answer 1

ejp wrote:
Of course it is. That's how any Map behavesWhen a key has been discarded its entry is effectively removed from the map, so this class behaves somewhat differently than other Map implementations. I meant, the mapping doesnt prevent the key from getting discarded cause it is a weakreference.
No: it's out of your control, but it's within the garbage collector's control. That is the purpose of the class.You aint talking about the situation written in this email. So if it is out of control, your suggestion about weakhashmap isn't gonna work. Out of control in the sense, it doesnt treat a key which was recently accessed any different from anything which wasn't accessed for a long time.
Because by choosing a key that will get garbage-collected at the time of interest to you, you ensure that the WeakHashMap will drop the corresponding value at the same time as the key is GC'd.Not realted to the problem above. Summarily WeakHashmap is no good for the above scenario.