subscribeservlet.java

JAVA Servlet2.3外文书籍源码

package personalPortal;

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

/**
 * Title:        Professional Java Servlet Programming - Chapter 2
 * Description:  Servlet to manage subscriptions to the newsletter(s).
 *               This will present the user with a form if they have not
 *               filled in the form, or process the request if the form
 *               has been completed.
 * Copyright:    Copyright (c) 2001
 * Company:
 * @author Andrew Harbourne-Thomas
 * @version 1.0
 */
public class SubscribeServlet extends GenericServlet implements DataMapping {

  /** Constant included as hidden value in the Subscription
   *  form so we know if this is a new request
   */
  public static final String SUB_FORM = "SubForm";

  /** used in subscription page as email parameter */
  public static final String EMAIL = "email";

  /** Daily subscription */
  public static final String DAILY = "Daily";

  /** Weekly subscription */
  public static final String WEEKLY = "Weekly";

  /** Monthly subscription */
  public static final String MONTHLY = "Monthly";

  /**
   * This processes requests to this servlet, determining if they
   * are new requests (to be given a form) or form submissions
   * for processing subscription requests
   *
   * @param request The object containing the client request
   * @param response The object used to send the response back
   */
  public void service(ServletRequest request, ServletResponse response)
    throws ServletException, IOException {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();

    String subscribeForm = request.getParameter(SUB_FORM);

    if (subscribeForm != null) {
      //its a subscribe request
      out.println(processSubscription(request));
    }
    else {
      //its a form request
      out.println(printForm());
    }
  }

  /**
   * This method processes subscription requests.  In this case we
   * perform little validation, but in a real world applciaiton
   * we would thoroughly validate the data, and then save it to a
   * database.
   *
   * @param request - the ServletRequest object (to extract parameters)
   */
  private StringBuffer processSubscription(ServletRequest request) {
    StringBuffer sub = new StringBuffer();
    String email = request.getParameter(EMAIL);
    String daily = request.getParameter(DAILY);
    String weekly = request.getParameter(WEEKLY);
    String monthly = request.getParameter(MONTHLY);

    //basic validation of email
    if (!isEmailOK(email)) {
      //failed validation
      sub.append("<h3>Error Processing Request</h3>");
      sub.append("Email entered is invalid.  Please go ");
      sub.append("<a href=\"javascript:history.go(-1)\">Back</a>");
      sub.append(" to try again.");
    }
    else {
      //here, if the request was successful, we would normally
      //save the data to a database
      sub.append("<h3>Request Processed</h3>");
      sub.append("<p>Your request is being processed. ");
      sub.append("You should receive an email confirmation shortly. ");
      sub.append("<p>Thank you.");
    }
    return sub;
  }

  /**
   * Performs Basic validation of the email address.
   *
   * @return Indicates if the email is OK (true), or failed validation (false)
   */
  private boolean isEmailOK(String emailToValidate) {
    if (emailToValidate == null ||
        emailToValidate.trim().length() == 0) {
      return false;
    }
    //check for an @
    int at = emailToValidate.indexOf("@");
    if (at == -1) {
      return false;
    }
    //check for a dot after the @
    int dot = emailToValidate.indexOf(".", at);
    if (dot == -1) {
      return false;
    }
    return true;
  }

  /**
   * This returns the form for the client to fill in.
   *
   * @return The HTML form
   */
  private StringBuffer printForm() {
    StringBuffer form = new StringBuffer();
    form.append("<form action=\"").append(PORTAL_RESOURCE);
    form.append("\" method=\"post\">");
    form.append("<input type=\"hidden\" name=\"");
    form.append(PORTAL_VIEW_PARAM_NAME).append("\" value=\"");
    form.append(PORTAL_VIEW_PARAM);
    form.append("\"><input type=\"hidden\" name=\"");
    form.append(PAGE_REQUESTED_NAME).append("\" value=\"");
    form.append(SUBSCRIBE_NAME);
    form.append("\"><input type=\"hidden\" name=\"");
    form.append(SUB_FORM).append("\" value=\"");
    form.append(SUB_FORM);
    form.append("\"><table align=\"center\" width=400>");
    form.append("<tr><td colspan=2><h3 align=\"center\">");
    form.append("Subscribe to the newsletters</h3></td></tr>");
    form.append("<tr><td width=\"50%\">Email Address</td>");
    form.append("<td width=\"50%\"><input type=\"text\" name=\"");
    form.append(EMAIL).append("\">");
    form.append("</td></tr><tr><td>Daily Newsletter</td>");
    form.append("<td><input type=\"checkbox\" name=\"");
    form.append(DAILY).append("\"></td></tr>");
    form.append("<tr><td>Weekly Newsletter</td>");
    form.append("<td><input type=\"checkbox\" name=\"");
    form.append(WEEKLY).append("\"></td></tr>");
    form.append("<tr><td>Monthly Newsletter</td>");
    form.append("<td><input type=\"checkbox\" name=\"");
    form.append(MONTHLY).append("\"></td></tr>");
    form.append("<tr><td colspan=2 align=center>");
    form.append("<input type=\"submit\" value=\"Submit Form\">");
    form.append("<input type=\"reset\" value=\"Clear Form\"></td></tr>");
    form.append("</table></form>");
    return form;
  }
}