Question

In a Java Servlet how can I change the value of an existing cookie? There is an addCookie method, but no deleteCookie or editCookie in HttpServletResponse

Answer 1

Those indeed don’t exist. Just create utility methods yourself which do that. Particularly getting the desired cookie is quite bloated. E.g.

public final class Servlets {

    private Servlets() {}

    public static Cookie getCookie(HttpServletRequest request, String name) {
        if (request.getCookies() != null) {
            for (Cookie cookie : request.getCookies()) {
                if (cookie.getName().equals(name)) {
                    return cookie;
                }
            }
        }

        return null;
    }

}

To edit a cookie, set its value and then add it to the response:

Cookie cookie = Servlets.getCookie(request, "foo");

if (cookie != null) {
    cookie.setValue(newValue);
    response.addCookie(cookie);
}

Set if necessary the maxage, path and domain as well if they differs from your default. The client namely doesn’t send this information back.

To delete a cookie, set the max age to 0 (and preferably also the value to null):

Cookie cookie = Servlets.getCookie(request, "foo");

if (cookie != null) {
    cookie.setMaxAge(0);
    cookie.setValue(null);
    response.addCookie(cookie);
}

Set if necessary the path and domain as well if they differs from your default. The client namely doesn’t send this information back.