Core Servlets and JavaServer Pages™

8.3. The Servlet Cookie API

To send cookies to the client, a servlet should create one or more cookies with designated names and values with new Cookie(name, value), set any optional attributes with cookie.setXxx (readable later by cookie.getXxx), and insert the cookies into the response headers with response.addCookie(cookie). To read incoming cookies, a servlet should call request.getCookies, which returns an array of Cookie objects corresponding to the cookies the browser has associated with your site (this is a zero-length but non-null array if there are no cookies in the request). In most cases, the servlet loops down this array until it finds the one whose name (getName) matches the name it had in mind, then calls getValue on that Cookie ...