This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
I don't know about web-console (it has not been working in the latest releases), but using jmx-console, in the jboss.jca:name=XXX,service=ManagedConnectionPool MBean (where XXX is the datasource name), you can find these attributes:
ConnectionCount - current number of connection to the database InUseConnectionCount - the number of those connections that are active (in use by some app)