can someone explain me the syntax of '${' and ':' in standalone.xml?

Question

can someone explain me the syntax of '${' and ':' in standalone.xml of JBoss (for example) , like in :

port-offset="${jboss.socket.binding.port-offset:0}" ?

I know 'jboss.socket.binding.port-offset' is a system properties . so if it is being set - it will overwrite the 0 value? what is the meaning of the ':' in this context ?

Answer 1

from here

As you can see it contains a Beanshell expression which means, unless the jboss.socket.binding.port-offset is set, it evaluates to 0 so to standard sockets.