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