Using a method to retrieve a cookie

[Derek Harper]

Hi guys,

I'm doing some experimenting with cookies. Below is code from a "Murach's Java Servlets & JSP" exercise to create a cookie that stores the first name of a user and adds it to the browser:

package download;
 
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
 
import business.User;
import data.UserIO;
 
public class RegisterUserServlet extends HttpServlet
{    
    @Override
    public void doPost(HttpServletRequest request,
            HttpServletResponse response)
            throws IOException, ServletException
    {      
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");
        String emailAddress = request.getParameter("emailAddress");
        
        User user = new User();
        user.setFirstName(firstName);
        user.setLastName(lastName);
        user.setEmailAddress(emailAddress);
 
        ServletContext sc = getServletContext();
        String path = sc.getRealPath("WEB-INF/EmailList.txt");
 
        UserIO.add(user, path);
        
        HttpSession session = request.getSession();
        session.setAttribute("user", user);
        String productCode = (String) session.getAttribute("productCode");
        
        Cookie emailCookie = new Cookie("emailCookie", emailAddress);
        emailCookie.setMaxAge(60*60*24*365*2); //set its age to 2 years
        emailCookie.setPath("/"); //allow the entire application to access it
        response.addCookie(emailCookie);
        
        //create cookie to store first name of user
        Cookie userCookie = new Cookie("user", firstName);
        userCookie.setPath("/");
        response.addCookie(userCookie);
        
        Cookie[] cookies = request.getKookies();
        String cookieName = "userCookie";
        String cookieValue = "";
        for (int i=0; i <cookies.length; i++)
        {
            Cookie cookie = cookies[i];
            if (cookieName.equals(cookie.getName()))
                cookieValue = cookie.getValue();
        }
        
        String url = "/" + productCode + "_download.jsp";
        RequestDispatcher dispatcher =
            getServletContext().getRequestDispatcher(url);
        dispatcher.forward(request, response);           
    }
    public void doGet(
            HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException, IOException
    {
        doPost(request, response);
    }
}
 
</CODE>
 
What I am trying to do is create an index.jsp file that will display a message that says "Welcome back, <first name of user>". I initially thought that I could use a scriptlet that uses the "getKookieValue" method to retrieve the cookie. 
 
 
So I tried the following code, but it didn't work:
 
 
<p><h1>Welcome back, 
 
    <% 
     String getKookieValue(
        Cookie[] cookies, String cookieName)
    {       
        String cookieValue = "";
        Cookie cookie;
        if (cookies != null)
        {
            for (int i=0; i<cookies.length; i++)
            {
                cookie = cookies[i];
                if (cookieName.equals(cookie.getName()))
                {
                    cookieValue = cookie.getValue();
                }
            }
        }
        return cookieValue;
%>
 
 

Yes, I know it's pretty "ugly" and i've spent hours trying to figure this out :-). Where am I going wrong? Please help. Thanks in advance.

[ September 17, 2008: Message edited by: Derek Harper ]
[ September 17, 2008: Message edited by: Derek Harper ]

[Steve Luke]

So I am going to do this in steps.

The first step is for academic purposes, I don't support actually doing this.

1) In JSPs, methods need to be declared in JSP Declarations, they are surround with <%! %> not <% %>. So your getKookieValue method should look like this:

<%! //<-- See now I am using Declaration, not Scriptlet
  String getKookieValue(Cookie[] cookies, String cookieName)
  {
    String cookieValue = "";
    Cookie cookie;
    if (cookies != null)
    {
      for (int i=0; i<cookies.length; i++)
      {
        cookie = cookies[i];
        if (cookieName.equals(cookie.getName()))
        {
          cookieValue = cookie.getValue();
        }
      }
    }
    return cookieValue;
  }
%>

This doesn't actually call the method, it just declares it, so use an Expression (<%= %>) to call the method and display the results:

<p><h1>Welcome back, <%= getKookieValue(request.getCookies(), "user") %></h1></p>

Like I said, I don't support using that, as it requires a lot of Java Code inside the JSP. This makes the JSP hard to manage and error-prone. The next option is the better one:

2) Use a controller servlet that gets called before this page (or every page). Use the Servlet to get the cookie value and store it in the request. Then use the JSP to retrieve the value from the request and display it:

//in servlet
    ...
    String userName = getKookieValue("user");
    request.setAttribute("user", userName);
    ...
    request.getRequestDispatcher(displaypage).forward(request,response);

//in JSP
  <p><h1>Welcome back, <%= request.getAttribute("user") %></h1></p>

[ August 08, 2008: Message edited by: Steve Luke ]

[Derek Harper]

Thanks for your reply Steve. I'll make sure to take into consideration what you recommended. I'm sorta "new" at this so I want to make sure I fully understand what's happening first.

Thanks again!

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