MyServlet.java Source code

Introduction

Here is the source code for MyServlet.java
Source

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

public class MyServlet extends HttpServlet {

    private Vector entries = new Vector();
    private long lastModified = 0;

    public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
        res.setContentType("text/html");
        PrintWriter out = res.getWriter();

        printHeader(out);
        printForm(out);
        printMessages(out);
        printFooter(out);
    }

    // Add a new entry, then dispatch back to doGet()
    public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
        handleForm(req, res);
        doGet(req, res);
    }

    private void printHeader(PrintWriter out) throws ServletException {
        out.println("<HTML><HEAD><TITLE>Guestbook</TITLE></HEAD>");
        out.println("<BODY>");
    }

    private void printForm(PrintWriter out) throws ServletException {
        out.println("<FORM METHOD=POST>"); // posts to itself
        out.println("<B>Please submit your feedback:</B><BR>");
        out.println("Your name: <INPUT TYPE=TEXT NAME=name><BR>");
        out.println("Your email: <INPUT TYPE=TEXT NAME=email><BR>");
        out.println("Comment: <INPUT TYPE=TEXT SIZE=50 NAME=comment><BR>");
        out.println("<INPUT TYPE=SUBMIT VALUE=\"Send Feedback\"><BR>");
        out.println("</FORM>");
        out.println("<HR>");
    }

    private void printMessages(PrintWriter out) throws ServletException {
        String name, email, comment;

        Enumeration e = entries.elements();
        while (e.hasMoreElements()) {
            GuestbookEntry entry = (GuestbookEntry) e.nextElement();
            name = entry.name;
            if (name == null)
                name = "Unknown user";
            email = entry.email;
            if (name == null)
                email = "Unknown email";
            comment = entry.comment;
            if (comment == null)
                comment = "No comment";
            out.println("<DL>");
            out.println("<DT><B>" + name + "</B> (" + email + ") says");
            out.println("<DD><PRE>" + comment + "</PRE>");
            out.println("</DL>");

            // Sleep for half a second to simulate a slow data source
            try {
                Thread.sleep(500);
            } catch (InterruptedException ignored) {
            }
        }
    }

    private void printFooter(PrintWriter out) throws ServletException {
        out.println("</BODY>");
    }

    private void handleForm(HttpServletRequest req, HttpServletResponse res) {
        GuestbookEntry entry = new GuestbookEntry();

        entry.name = req.getParameter("name");
        entry.email = req.getParameter("email");
        entry.comment = req.getParameter("comment");

        entries.addElement(entry);

        // Make note we have a new last modified time
        lastModified = System.currentTimeMillis();
    }

    public long getLastModified(HttpServletRequest req) {
        return lastModified;
    }
}

class GuestbookEntry {
    public String name;
    public String email;
    public String comment;
}