Handling cookies in the Jakarta Servlet API is simple and straightforward. Cookies are small bits of data sent from a server to a client and then sent back by the client in subsequent requests to the server. Below is how you can handle cookies using Jakarta Servlet API:
1. Creating and Adding a Cookie
To create a cookie, use the jakarta.servlet.http.Cookie class. You can add the cookie to the response using the HttpServletResponse object.
Example: Adding a Cookie
package org.kodejava.servlet;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/addCookie")
public class AddCookieServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// Create a new cookie
Cookie cookie = new Cookie("username", "john_doe");
// Set cookie properties
cookie.setMaxAge(24 * 60 * 60); // 1 day (in seconds)
cookie.setHttpOnly(true); // Makes it inaccessible to JavaScript
cookie.setSecure(true); // Send it only over HTTPS
// Add the cookie to the response
response.addCookie(cookie);
response.getWriter().println("Cookie has been set!");
}
}
2. Reading Cookies
To read cookies, use the HttpServletRequest object to retrieve all cookies with the getCookies() method, and then search for the desired cookie.
Example: Retrieving a Cookie
package org.kodejava.servlet;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/readCookie")
public class ReadCookieServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Cookie[] cookies = request.getCookies();
if (cookies != null) {
for (Cookie cookie : cookies) {
if ("username".equals(cookie.getName())) {
response.getWriter().println("Found cookie: "
+ cookie.getName() + " = "
+ cookie.getValue());
return;
}
}
}
response.getWriter().println("Cookie not found!");
}
}
3. Deleting a Cookie
To delete a cookie, set its maximum age to 0 and add it back to the response. When the browser sees the cookie with a 0 age, it will remove it.
Example: Deleting a Cookie
package org.kodejava.servlet;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
public class DeleteCookieServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Cookie[] cookies = request.getCookies();
if (cookies != null) {
for (Cookie cookie : cookies) {
if ("username".equals(cookie.getName())) {
Cookie deleteCookie = new Cookie("username", "");
deleteCookie.setMaxAge(0); // Mark cookie for deletion
response.addCookie(deleteCookie);
response.getWriter().println("Cookie has been deleted!");
return;
}
}
}
response.getWriter().println("Cookie not found!");
}
}
Important Notes
- Secure Cookies: Always mark cookies as secure (
cookie.setSecure(true)) if you’re using HTTPS, to prevent transmission over unsecured connections. - HttpOnly Flag: Use
cookie.setHttpOnly(true)to prevent cookies from being accessed via client-side scripts, enhancing security. - Path and Domain Settings: Cookies can be restricted to certain paths or domains to control their scope:
cookie.setPath("/secure"); cookie.setDomain(".example.com"); - Cookie Expiration:
cookie.setMaxAge(x): Sets the lifespan in seconds.x = 0deletes the cookie, andx = -1makes it a session cookie (deleted when the browser is closed).
Maven dependencies
<dependency>
<groupId>jakarta.servlet</groupId>
<artifactId>jakarta.servlet-api</artifactId>
<version>6.1.0</version>
<scope>provided</scope>
</dependency>
