Apparentely this seems a silly question, however at a job interview you might be surprised to hear the question: "How do you find out the JBoss version you are running ?" (Provided that you don't have access to the server logs).
Well in real world cases, it's rare that you need to operate on an application server without access to the server logs. If you look at the server logs, every application server release boots with information about the server version:
10:23:56,860 INFO [Server] Release ID: JBoss [Trinity] 4.2.2.GA (build: SVNTag=JBoss_4_2_2_GA date=200710221139)
However interview questions are seldom based on real case examples but more often used to test if you are a smart guy or not. So, in releases 4.X to 6.X you can find it using the jmx-console digging into the jboss.system domain. The following MBean request to find out the JBoss version you are running:
http://localhost:8080/jmx-console/HtmlAdaptor?action=inspectMBean&name=jboss.system%3Atype%3DServer
Which will return a set of Server properties including the release of the application server:
As far as it concerns JBoss AS 7, well, it's pretty visible from the welcome page that you are running JBoss AS 7. If you need to find out the exact JBoss version, just navigate to the administration Web console and will check it:
http://localhost:9990/console/App.html#server-overview
By the way, JBoss AS 7 includes also the --version flag which allows (at startup) to check the server version:
C:\jboss-as-7.1.1.Final\bin>standalone.bat --version
Calling "C:\jboss-as-7.1.1.Final\bin\standalone.conf.bat"
. . . . .
10:41:54,621 INFO [org.jboss.modules] JBoss Modules version 1.1.1.GA
JBoss AS 7.1.1.Final "Brontes"
Press any key to continue . . .