How exactly Spring MVC handle cookie? - spring

Question

I am studying how Spring handle cookie on a tutorial and I have some doubts.
In this example there is this CookieControllerExample that perform some cookie operation when are performed.
#Controller
public class CookieControllerExample {
#RequestMapping(value = "/readcookie", method=RequestMethod.GET)
public ModelAndView readCookie(#CookieValue(value = "URL") String URL, HttpServletRequest request,
HttpServletResponse response) {
System.out.println("CookieControllerExample readcookie is called");
return new ModelAndView("/cookie/cookieView", "cookieValue", URL);
}
#RequestMapping(value = "/writecookie", method=RequestMethod.GET)
public String writeCookie(HttpServletRequest request,
HttpServletResponse response) {
System.out.println("CookieControllerExample writeCookie is called");
Cookie cookie = new Cookie("URL", request.getRequestURL().toString());
response.addCookie(cookie);
return "/cookie/cookieView";
}
#RequestMapping(value = "/readAllCookies", method=RequestMethod.GET)
public ModelAndView readAllCookies(HttpServletRequest request) {
System.out.println("CookieControllerExample readAllCookies is called");
Cookie[] cookies = request.getCookies();
System.out.println("All Cookies in your browsers");
String cookiesStr = "";
for(Cookie cookie : cookies){
System.out.println(cookie.getName() + " : " + cookie.getValue());
cookiesStr += cookie.getName() + " : " + cookie.getValue() + "<br/>";
}
return new ModelAndView("/cookie/cookieView", "cookieValue", cookiesStr);
}
}
From what I have understand the first method (readcookie()) read the content of a coockie named URL stored inside my computer.
The second method (writecookie()) create a cookie named URL and store it on my computer.
And the third method read the contet of all the cookies stored on my computer.
I have 2 doubts:
1) I know that cookies are textual file. Where exactly are stored?
2) Why the **writeCookie() method, after create a new cookie, add it to the response? How can I examinate the cookie stored on my system?
response.addCookie(cookie);
I think that it could depend by the fact that the response come back to the user browser and it retrieve the cookie from this response and create a textual file somewhere on my system. Is it true or am I missing something?

Answer 1

You asked:
1) I know that cookies are textual file. Where exactly are stored?
The cookies are stored by the clients browser, somewhere at the clients machine. - The exact location depends on the browser
2) Why the **writeCookie() method, after create a new cookie, add it to the response? How can I examinate the cookie stored on my system?
As I told in answer for question 1), the cookie is stored at client side. So it's values need to be send to the client (in the header of the http-response). And that is the reason why the cookie (object) is added to the http response.
I strongly recommend you to read the wikipedia article about Http Cookies. And do not get confused by mixing cookies and sessions (sessions are often implement with a session-tracking-cookie, but its data resist on the server side.)