📄 cookieservlet.java

📁 java web services how to program
💻 JAVA
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// Fig. A.19: CookieServlet.java
// Using cookies to store data on the client computer.
package com.deitel.jws.servlets;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

public class CookieServlet extends HttpServlet {
   private final Map books = new HashMap();

   // initialize Map books
   public void init()
   {
      books.put( "C", "0130895725" );
      books.put( "C++", "0130895717" );
      books.put( "Java", "0130125075" );
      books.put( "VB6", "0134569555" );
   }

   // receive language selection and send cookie containing
   // recommended book to the client
   protected void doPost( HttpServletRequest request,
      HttpServletResponse response )
         throws ServletException, IOException
   {
      String language = request.getParameter( "language" );
      String isbn = books.get( language ).toString();
      Cookie cookie = new Cookie( language, isbn );

      response.addCookie( cookie );  // must precede getWriter 
      response.setContentType( "text/html" );
      PrintWriter out = response.getWriter();         

      // send XHTML page to client

      // start XHTML document
      out.println( "<?xml version = \"1.0\"?>" );

      out.println( "<!DOCTYPE html PUBLIC \"-//W3C//DTD " +
         "XHTML 1.0 Strict//EN\" \"http://www.w3.org" +
         "/TR/xhtml1/DTD/xhtml1-strict.dtd\">" ); 

      out.println( 
         "<html xmlns = \"http://www.w3.org/1999/xhtml\">" );
      
      // head section of document
      out.println( "<head>" );
      out.println( "<title>Welcome to Cookies</title>" );      
      out.println( "</head>" );

      // body section of document
      out.println( "<body>" );
      out.println( "<p>Welcome to Cookies! You selected " +
         language + "</p>" );

      out.println( "<p><a href = " +
         "\"/jws/servlets/CookieSelectLanguage.html\">" +
         "Click here to choose another language</a></p>" );

      out.println( "<p><a href = \"/jws/cookies\">" + 
         "Click here to get book recommendations</a></p>" );
      out.println( "</body>" );

      // end XHTML document
      out.println( "</html>" );
      out.close();    // close stream
   }

   // read cookies from client and create XHTML document
   // containing recommended books
   protected void doGet( HttpServletRequest request,
      HttpServletResponse response )
         throws ServletException, IOException
   {
      Cookie cookies[] = request.getCookies();  // get cookies

      response.setContentType( "text/html" ); 
      PrintWriter out = response.getWriter();

      // start XHTML document
      out.println( "<?xml version = \"1.0\"?>" );

      out.println( "<!DOCTYPE html PUBLIC \"-//W3C//DTD " +
         "XHTML 1.0 Strict//EN\" \"http://www.w3.org" +
         "/TR/xhtml1/DTD/xhtml1-strict.dtd\">" ); 

      out.println( 
         "<html xmlns = \"http://www.w3.org/1999/xhtml\">" );

      // head section of document
      out.println( "<head>" );
      out.println( "<title>Recommendations</title>" );
      out.println( "</head>" );

      // body section of document
      out.println( "<body>" );

      // if there are any cookies, recommend a book for each ISBN
      if ( cookies != null && cookies.length != 0 ) {
         out.println( "<h1>Recommendations</h1>" );
         out.println( "<p>" );

         // get the name of each cookie
         for ( int i = 0; i < cookies.length; i++ ) 
            out.println( cookies[ i ].getName() + 
               " How to Program. ISBN#: " + 
               cookies[ i ].getValue() + "<br />" );

         out.println( "</p>" );
      }
      else {   // there were no cookies
         out.println( "<h1>No Recommendations</h1>" );
         out.println( "<p>You did not select a language.</p>" );
      }

      out.println( "</body>" );

      // end XHTML document
      out.println( "</html>" );
      out.close();    // close stream
   }
}
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