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🔔 Subscribe to Ram N JavaWorking with Cookies in Java Servlets
Cookies are small textual key-value pairs created on the server and stored on the client browser. They are one of the most widely used mechanisms for session tracking, storing user preferences, and remembering login details across requests.
The Java Servlet API makes it simple to manage cookie lifecycles using the jakarta.servlet.http.Cookie (or javax.servlet.http.Cookie) class.
1. How to Create and Send a Cookie
To create a cookie and attach it to the HTTP response, instantiate a Cookie object with a key and value, optionally set its max age, and add it using HttpServletResponse:
userCookie.setMaxAge(60 * 60 * 24); // Persistent for 24 hours (in seconds)
response.addCookie(userCookie);
2. How to Retrieve Cookies from a Request
When a browser makes a request, it sends back stored cookies in the request header. You can read them by calling getCookies() on HttpServletRequest:
if (cookies != null) {
for (Cookie c : cookies) {
if ("username".equals(c.getName())) {
String value = c.getValue();
}
}
}
3. How to Delete a Cookie
The Servlet API does not provide a direct deleteCookie() method. To delete an existing cookie from the client's browser, you overwrite it by setting its maximum age to zero (0) and sending it back:
deleteCookie.setMaxAge(0); // Deletes immediately
response.addCookie(deleteCookie);
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