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CS6320 – Servlet Cookies. L. Grewe. What is a cookie?. Name-value bindings sent by a server to a web browser and then sent back unchanged by the browser each time it accesses that server. e.g. login = grewe (name = value) - PowerPoint PPT Presentation
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CS6320 – Servlet CS6320 – Servlet CookiesCookies
L. GreweL. Grewe
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What is a cookie?What is a cookie? Name-value bindings sent by a server to a Name-value bindings sent by a server to a
web browser and then sent back web browser and then sent back unchanged by the browser each time it unchanged by the browser each time it accesses that server.accesses that server.• e.g. login = grewe e.g. login = grewe (name = value)(name = value)
Used for Used for authenticatingauthenticating, tracking, and , tracking, and maintaining specific information about maintaining specific information about users, such as site preferences or the users, such as site preferences or the contents of their contents of their electronic shopping cartselectronic shopping carts. .
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Servlets and CookiesServlets and Cookies Java Servlet API provides comfortable Java Servlet API provides comfortable
mechanisms to handle cookiesmechanisms to handle cookies The class The class javax.servlet.http.Cookiejavax.servlet.http.Cookie represents a represents a
cookiecookie• Getter methods: Getter methods:
getName()getName(), , getValue()getValue(), , getPath()getPath(), , getDomain()getDomain(), , getMaxAge()getMaxAge(), , getSecure()getSecure()……
• Setter methods: Setter methods: setValue()setValue(),, setPath() setPath(), , setDomain()setDomain(),,
setMaxAge()setMaxAge()……
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Servlets and Cookies (cont)Servlets and Cookies (cont)
Get the cookies from the service Get the cookies from the service request:request:
Cookie[]Cookie[] HttpServletRequest.getCookies() HttpServletRequest.getCookies()
Add a cookie to the service response:Add a cookie to the service response:HttpServletResponse.addCookie(Cookie cookie)HttpServletResponse.addCookie(Cookie cookie)
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Webpage that triggers Servlet to Webpage that triggers Servlet to create a Cookiecreate a Cookie
<html> <head><title>Insert your Name</title></head> <body> <h1>What is your name?</h1> <form action="welcomeback" method="get"> <p> <input type="text" name="username" /> <input type="submit" /> </p> </form> </body></html>
getname.html
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An Example (cont)An Example (cont)
public class WelcomeBack extends HttpServlet {public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { String user = req.getParameter("username"); if (user == null) { // Find the "username" cookie Cookie[] cookies = req.getCookies(); for (int i = 0; cookies != null && i < cookies.length; ++i) { if (cookies[i].getName().equals("username")) user = cookies[i].getValue(); } } else res.addCookie(new Cookie("username", user));
WelcomeBack.java
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An Example (cont)An Example (cont) if (user == null) // No parameter and no cookie res.sendRedirect("getname.html");
res.setContentType("text/html"); PrintWriter out = res.getWriter(); out.println("<html><body><h1>Welcome Back " + user + "</h1></body></html>");
}} WelcomeBack.java
