How can I find out the amount of open sessions programatically in Tomcat using Java?

Question

Is it possible to find out the number of open sessions reliably in Tomcat (i.e. not only the amount of users who have logged in since [current time]-[session time out], but the number of sessions stored on the server)?

Answer 1

You can find this info using JMX. See here for how to enable JMX and what variables to query.

Using an Ant JMX task you can use:

   <!-- get all sessions and split result as delimiter <em>SPACE</em> for easy
             access all session ids directly with ant property sessions.[0..n].
        -->
        <jmx:invoke
            name="Catalina:type=Manager,path=/ClusterTest,host=localhost" 
            operation="listSessionIds"
            resultproperty="sessions"
            echo="false"
            delimiter=" "
        />

but you can use other tools e.g. JConsole.

Answer 2

You can find this with the builtin Manager as well at http://server:8080/manager/status

If you don't have an admin login enabled, edit conf/tomcat-users.xml and add a user with role="admin". More info in the Tomcat documentation here.

Answer 3

If you need this info in your application, you can trace when sessions are created or destroyed by implementing HttpSessionListener and adding it to your server context.

http://java.sun.com/javaee/5/docs/api/javax/servlet/http/HttpSessionListener.html