code: public void setRoleMembership(String subject, Set<String> roles) {
  		validateStringValue(subject);
  		Validate.notNull(roles);
  		if(roles.isEmpty())
  			return;
  		Validate.noNullElements(roles);
  		
  		props.setProperty(String.format(ROLE_MEMBERSHIP_FORMAT, subject), ArrayUtils.toString(encapsulateValues(roles)));
  	}
docs: -- Role membership