java - Cookie troubles with Spring MVC -

i trying cookie value using @cookie. 400 error if cookie value null. what's wrong? controller:

    public string listcontacts(map<string, object> map,             httpservletresponse response, @cookievalue("flag") string flag) {            response.addcookie(new cookie("flag", "in use")); ... 

try setting required = false in @cookievalue annotation:

public string listcontacts(map<string, object> map,       httpservletresponse response, @cookievalue(value = "flag", required = false) string flag) { 

by default spring expects cookie header present , throws exception otherwise:

default true, leading exception being thrown in case header missing in request. switch false if prefer null in case of missing header.

alternatively, provide defaultvalue, implicitly sets flag false.