Spring MVC的java Cookie问题

Question

我试图使用@Cookie获取cookie值。但如果cookie值为空，我会得到400个错误。发生了什么？ 这是我的控制器：

    public String listContacts(Map<String, Object> map,
            HttpServletResponse response, @CookieValue("flag") String flag) {



        response.addCookie(new Cookie("flag", "In use"));
...

Answer 1

尝试在@CookieValue注释中设置required = false：

public String listContacts(Map<String, Object> map,
      HttpServletResponse response, @CookieValue(value = "flag", required = false) String flag) {

默认情况下，spring希望cookie头出现，否则抛出异常：

Default is true, leading to an exception being thrown in case the header is missing in the request. Switch this to false if you prefer a null in case of the missing header.

Alternatively, provide a defaultValue, which implicitly sets this flag to false.