Set session value as empty while creating it

HI team,

exec { session =>

  session.set("ComNodeStatus", 100).set("commCount", 0).set("Commodities", "")

I have the commodities and I set as "" but I wanted to find an alternate to this. Is there anyway I can set as empty/null while creating the session variable? (any expression language?

I am new to jawline tool can anybody help me out how to do correlation for authentic token which will generate from server and its dynamically change and where will i get the response data for that particular value.