How to set global properties in JBoss

Hello!

We are porting a web-app from Weblogic 7 to JBoss 4.3

I need to set some System.properties in my JBoss 4.3 so I can get them like:
String theProp = System.getProperty("my.special.prop");

In Weblogic this was possible with:
<StartupClass
        Arguments="globalpropertyfile=c:\dev\wlsdomains\mydomain\global.properties"
        ClassName="com.ourown.InitGlobalProperties"
        FailureIsFatal="true" Name="InitGlobalProperties" Targets="myserver"/>
       
...in a config.xml where the prop was specified in the file global.properties.

Hope that some one got an idea how to do this in JBoss!

Best regards
Fredrik