In a Java Servlet how can I change the value of an existing cookie?

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.

Answer 2

Here is an example from kodejava:

 public class ReadCookieExample extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse   response)         throws    ServletException, IOException {
    response.setContentType("text/html");
    PrintWriter writer = response.getWriter();

    Cookie[] cookies = request.getCookies();
    for (int i = 0; i < cookies.length; i++) {
        writer.println("Name: " + cookies[i].getName() + "; Value: "                    +                   cookies[i].getValue());            
    }
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws    ServletException, IOException {
    doPost(request, response);
}

}

That will get the cookies list, get the one you want and instead of printing out values, do something similar to this:

 cookie.setValue(String.valueOf(<new Value>));  
 cookie.setMaxAge(60*60*24*365);   
 cookie.setPath("/");   
 response.addCookie(cookie);  etc...

HTH,

James