java - How to get all properties name from groovy template -

i use groovy template java code:

import groovy.text.simpletemplateengine  string template = 'hello, $firstname <%print lastname%>!';  map vars = new hashmap<string, string>(); vars.put("firstname", "john"); vars.put("lastname", "doe");  simpletemplateengine engine = new simpletemplateengine(); writable w = engine.createtemplate(template).make(vars);  system.out.println(w.tostring()); 

how list off properties name template, e.g.:

• firstname
• lastname

?