Servlets - An Introduction to Network Programming with Java

Java Reference

In-Depth Information

void setComment(String <value>)

(A comment is optionally used to describe the cookie.)

String getComment()

String getName()

String getValue()

void setValue(String <value>)

int getMaxAge()

Example

This will be a modifi cation of the earlier 'Simple Adder' example. On the user's fi rst

visit to the site, he/she will be prompted to enter his/her name and a choice of both

foreground and background colours for the addition result page. These values will be

saved in cookies, which will be retrieved on subsequent visits to the site. If the user fails

to enter a name, there will be no personalised header. Failure to select a foreground

colour will result in a default value of black being set, whilst failure to select a back-

ground colour will result in a default value of white being set. The only differences in

the initial HTML fi le are in the lines giving the names of the two fi les involved:

.............................................

.............................................

Servlet CookieAdder will set up a new Session object, retrieve the user's cookies

and create session variables corresponding to those cookies. (A Session object is

preferable, since three servlets will be involved, all of which require access to the

data values. This saves each servlet from having to download the cookies sepa-

rately.) In addition to the contents of the cookies, the result of the addition will need

to be saved in a session variable. If the appropriate session variable indicates that

this is the user's fi rst visit to the site, method sendRedirect will be used to pass con-

trol to a preferences servlet. In order to avoid code duplication, control will also

need to be redirected to a result-displaying servlet from both the initial servlet and

the preferences servlet.

Here's the code for CookieAdder (the initial servlet):

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

import javax.servlet.annotation.WebServlet;

@WebServlet("/CookieAdder")

public class CookieAdder extends HttpServlet

{

public void doPost(HttpServletRequest request,

HttpServletResponse response)

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