📄 guestbook.java
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import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.oreilly.servlet.CacheHttpServlet;
public class Guestbook extends CacheHttpServlet {
private Vector entries = new Vector(); // User entry list
private long lastModified = 0; // Time last entry was added
// Display the current entries, then ask for a new entry
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;
}
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