/*
* @(#)SurveyServlet.java
*
* Copyright (c) 1995, 2004, Oracle. All rights reserved.  
*
* This software is the confidential and proprietary information of Sun
* Microsystems, Inc. ("Confidential Information").  You shall not
* disclose such Confidential Information and shall use it only in
* accordance with the terms of the license agreement you entered into
* with Sun.
* 
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
* SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*/

import java.io.*;
import java.util.*;

import javax.servlet.*;
import javax.servlet.http.*;

/**
 * A sample single-threaded servlet that takes input from a form
 * and writes it out to a file.  It is single threaded to serialize
 * access to the file.  After the results are written to the file,
 * the servlet returns a "thank you" to the user.
 * <p/>
 * <p>You can run the servlet as provided, and only one thread will run
 * a service method at a time.  There are no thread synchronization
 * issues with this type of servlet, even though the service method
 * writes to a file.  (Writing to a file within a service method
 * requires synchronization in a typical servlet.)
 * <p/>
 * <p>You can also run the servlet without using the single thread
 * model by removing the <tt>implements</tt> statement.  Because the
 * service method does not synchronize access to the file, multiple
 * threads can write to it at the same time.  When multiple threads try
 * to write to the file concurrently, the data from one survey does not
 * follow the data from another survey in an orderly fashion.
 * <p/>
 * <p>To see interaction (or lack of interaction) between threads, use
 * at least two browser windows and have them access the servlet as
 * close to simultaneously as possible.  Expect correct results (that
 * is, expect no interference between threads) only when the servlet
 * implements the <code>SingleThreadedModel</code> interface.
 */

public class SurveyServlet extends HttpServlet
        implements SingleThreadModel {
    String resultsDir;


    public void init(ServletConfig config)
            throws ServletException {
        super.init(config);
        resultsDir = getInitParameter("resultsDir");
        if (resultsDir == null) {
            Enumeration initParams = getInitParameterNames();
            System.err.println("The init parameters were: ");
            while (initParams.hasMoreElements()) {
                System.err.println(initParams.nextElement());
            }
            System.err.println("Should have seen one parameter name");
            throw new UnavailableException(this,
                                           "Not given a directory to write survey results!");
        }
    }


    /**
     * Write survey results to output file in response to the POSTed
     * form.  Write a "thank you" to the client.
     */
    public void doPost(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {
        // first, set the "content type" header of the response
        res.setContentType("text/html");

        //Get the response's PrintWriter to return text to the client.
        PrintWriter toClient = res.getWriter();

        try {
            //Open the file for writing the survey results.
            String surveyName = req.getParameterValues("survey")[0];
            FileWriter resultsFile = new FileWriter(resultsDir
                                                    + System.getProperty("file.separator")
                                                    + surveyName + ".txt", true);
            PrintWriter toFile = new PrintWriter(resultsFile);

            // Get client's form data & store it in the file
            toFile.println("<BEGIN>");
            Enumeration values = req.getParameterNames();
            while (values.hasMoreElements()) {
                String name = (String) values.nextElement();
                String value = req.getParameterValues(name)[0];
                if (name.compareTo("submit") != 0) {
                    toFile.println(name + ": " + value);
                }
            }
            toFile.println("<END>");

            //Close the file.
            resultsFile.close();

            // Respond to client with a thank you
            toClient.println("<html>");
            toClient.println("<title>Thank you!</title>");
            toClient.println("Thank you for participating");
            toClient.println("</html>");

        } catch (IOException e) {
            e.printStackTrace();
            toClient.println("A problem occured while recording your answers.  "
                             + "Please try again.");
        }

        // Close the writer; the response is done.
        toClient.close();
    }
}