Determing session size

Question

Dear all,
Had a look at the API and googled no luck sofar.
Whats the standard way of determining the size of the session object, on the server ? We need to log this info for our application.
I fear that we must persist the session object to the file-system as a file, and determine size this way. Does anyone know of an easier solution?
thanks in advance.
Ben

Answer 1

Not sure about a link. It was on these forums, I think in the Java Programming Forum:
<http://forum.java.sun.com/forum.jspa?forumID=31>
And I believe it was uj or UlrikaJ that described it. It wasn't specifically about sessions, but about Java Objects in general.
One thing to note is: in order for it to work, all the objects in the session must be Serializable (<http://java.sun.com/j2se/1.5.0/docs/api/java/io/Serializable.html>). The HttpSession is an interface which does not extend the Serializable interface, so you can't count on the session itself being serializable. You may need to wrap it in a class of your own before you serialize to handle serializing its contents using readObject and writeObject. In practice, Session objects probably will be serializable since they often get persisted to disk or DB when memory is low, and are passed around servers when using clustering. But that would be an implementation detail particular to each server.
For a general overview of Serialization, see:
<http://java.sun.com/docs/books/tutorial/essential/io/serializing.html>
And substitue java.io.ByteArrayOutputStream (<http://java.sun.com/j2se/1.5.0/docs/api/java/io/ByteArrayOutputStream.html>) for the FileOutputStream in the code.