I am planning to use JGroups in a web application.
JGroups by default uses IPv6 for multicasting of messages. JGroups can only be configured to use IPv4 by setting a property like the following (see docs)
-Djava.net.preferIPv4Stack=true
This does not work if set in code. What are my options when running a war file in an application server for setting this property, specifically tomcat and glassfish?
Unless you have a specific reason to put this in code, it can easily be configured for Tomcat by setting the environment variable CATALINA_OPTS (to -Djava.net.preferIPv4Stack=true). I think the proper place to do this is to create ${CATALINA_HOME}/bin/setenv.sh and place the setting in there.