user manual

74 BES Developer’s Guide
Using HTTP sessions
Object myState = session.getAttribute("myState");
// Modify mystate here and do not call setAttribute ()
Your configuration file, server.xml, will have the following code snippet:
<Manager className=
"org.apache.catalina.session.PersistentManager"
maxIdleBackup="xxx">
<Store className=
"org.apache.catalina.session.BorlandStore"
storeName="jss_factory">
</Manager>
where xxx is the time interval in seconds that you want the session data to be
stored.
For more information about the server.xml file, go to Chapter 5, “Web server to
web container connectivity”.
Note When using the Automatic implementation, you need to consider the following
limitations:
1 If the web container goes down between two save intervals, the latest
changes are not visible for the next web container instance. This is an
important concern when defining the time interval value for the heartbeat.
2 The data is saved at the specified time interval no matter if the data is
changed or not. This can be wasteful if a session frequently does not
change and the defined time interval value is set too low.
Using HTTP sessions
The HyperText Transfer Protocol (HTTP) is a stateless protocol. In the client/
server paradigm, it means that all client requests that the Apache web server
receives are viewed as independent transactions. There is no relationship
between each client request. This is a typical stateless connection between
the client and the server.
However, there are times when the client deems it necessary to have a
session concept for transaction completeness. A session concept typically
means having a stateful interaction between the client and server. An example
of the session concept is shopping online with an interactive shopping cart.
Every time you add a new item into your shopping cart, you expect to see that
new item added to a list of previously added items. HTTP is not usually
regarded for handling client request in a stateful manner. But it can.
BES supports the HTTP sessions through two methods of implementations:
■
Cookies: The web server send a cookie to identify a session. The web
browser keeps sending back the same cookie with future requests. This
cookie helps the server-side components to determine how to handle the
transaction for a given session.