Setting system properties for WildFly with a properties file

To set or override system properties without changing WildFly's configuration there is a CLI parameter "-p".

Assuming you have a property file vweber.properties in /dev/veit/wildfly/ with the following content

mightyapplication.property=somevalue  

and start your WildFly with

/wildfly-10.0.0.Final/bin/standalone.sh -P=/dev/veit/wildfly/vweber.properties

the call of

return System.getProperty(key);  

should return somevalue.