Servlet II Anwendungen • Formular Auswertung • Zähler • Zähler mit Zwischenspeicherung • Hintergrund Berechnung • Passwort Abfrage
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Servlet II
Anwendungen• Formular Auswertung
• Zähler
• Zähler mit Zwischenspeicherung
• Hintergrund Berechnung
• Passwort Abfrage
Auswertung eines Formulars
Servlet Container
processformular
http://www.sdf.... Webserver
index.html
Response
Response
Post Request
Get Request
<FORM>
<form method="POST" action="processformular">
<input type="text" name=name size=50 >
<input type="submit" >
</form>
http
Request
HTML
Formular
Servlet
Auswertung
get <form method=“GET" doGet(…
post <form method="POST" doPost(…
HTML
Formular erstellen
Auswertung
package counter;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.util.*;
public class formular extends HttpServlet { private static final String CONTENT_TYPE = "text/html";
public void init() throws ServletException { }
public void doPost(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException {
response.setContentType(CONTENT_TYPE); PrintWriter out = response.getWriter(); String name = req.getParameter("name"); String s1 = req.getParameter("is-gift"); String s2 = req.getParameter("address-line-1"); String s3 = req.getParameter("address-line-2"); String s4 = req.getParameter("city");
Auswertung
String s5 = req.getParameter("state"); String s6 = req.getParameter("country"); String s7 = req.getParameter("phone-number"); String s8 = req.getParameter("shipping-billing"); out.println("<HTML>"); out.println("<HEAD><TITLE>Formular</TITLE></HEAD>"); out.println("<BODY>"); out.println("Name: " + name +"<BR>"); out.println("Geschenk: " + s1 +"<BR>"); out.println("Adr: " + s2 +"<BR>"); out.println("Adr2: " + s3 +"<BR>"); out.println("Stadt: " + s4 +"<BR>"); out.println("Land: " + s6 +"<BR>"); out.println("Tel: " + s7 +"<BR>"); out.println("Rechnung: " + s8 +"<BR>"); out.println("</BODY></HTML>"); } public void destroy() {}}
Simple Counter
package counter;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class SimpleCounter extends HttpServlet {
int count = 0;
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
count++;
out.println("Since loading, this servlet has been accessed " + count + " times.");
}
}
Internet Mehrfach Anfragen
Daten Inkonsistenz
Kein Problem bei lokalen Variablen Vorsicht bei Instanz VariablenBsp: Simple Counter count++; // Thread 1 count++; // Thread 2 out.println("Since loading, ….. // Thread 1 out.println("Since loading, ….. // Thread 2
Hilfe: synchronized Blocks:Nur ein einzelner Thread darf einen synchronized Block ausführen
Simple Counter synchronized
package counter;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class SimpleCounter extends HttpServlet {
int count = 0;
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
synchronized(this) { count++;
out.println("Since loading, this servlet has been accessed "+count +" times.");
}
}
}
Counter IIpackage counter;
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HolisticCounter extends HttpServlet {
static int classCount = 0; // verteilt auf alle Instanzen
int count = 0; // Nur für dieses Servlet
static Hashtable instances = new Hashtable(); // verteilt auf alle Instanzen
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
count++;
out.println("Since loading, this servlet instance has been accessed " +
count + " times.");
Counter II
// Trick: Die Instanzen werden gezählt, indem sie in eine
// Hashtable eingetragen werden. Gleiche Einträge werden ignoriert.
// Die size() Methode liefert die Zahl der einzelnen Instanzen.
instances.put(this, this);
out.println("There are currently " +
instances.size() + " instances.");
classCount++;
out.println("Across all instances, this servlet class has been " +
"accessed " + classCount + " times.");
}
}
Lebenszyklus
• Initialisierung
• Antworten auf Anfragen
• Zerstörung
Persistenz
DB Verbindung
Information von früheren Transaktionen
Counter III
package counter;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class InitDestroyCounter extends HttpServlet {
int count;
public void init() throws ServletException {
// Versuch den gespeicherten Zustand des Zählers zu laden
FileReader fileReader = null;
BufferedReader bufferedReader = null;
try {
fileReader = new FileReader("InitDestroyCounter.initial");
bufferedReader = new BufferedReader(fileReader);
String initial = bufferedReader.readLine();
count = Integer.parseInt(initial);
return;
}
catch (FileNotFoundException ignored) { } // kein gespeicherter Zähler catch (IOException ignored) { } // Problem beim lesen catch (NumberFormatException ignored) { } // Korruptes File finally { // Schliessen des Files try { if (bufferedReader != null) {bufferedReader.close(); } } catch (IOException ignored) { } } // Überprüfe ob ein Initialisierungsparameter vorhanden ist. String initial = getInitParameter("initial"); try { count = Integer.parseInt(initial); return; } catch (NumberFormatException ignored) { } // null or non-integer value // Default 0 count = 0; }
InitDestroyCounter
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
count++;
out.println("Since the beginning, this servlet has been accessed " +
count + " times.");
}
public void destroy() {
super.destroy();
saveState();
}
InitDestroyCounter
public void saveState() {
// Versuch den Counter zu speichern
FileWriter fileWriter = null;
PrintWriter printWriter = null;
try {
fileWriter = new FileWriter("InitDestroyCounter.initial");
printWriter = new PrintWriter(fileWriter);
printWriter.println(count);
return;
}
catch (IOException e) { // Problem beim Schreiben
}
finally {
// Zur Sicherheit das File schliessen
if (printWriter != null) {
printWriter.close();
}
}
}
}
InitDestroyCounter
PrimSearcher
package counter;import java.io.*;import java.util.*;import javax.servlet.*;import javax.servlet.http.*;
public class PrimeSearcher extends HttpServlet implements Runnable {
long lastprime = 0; // letzte gefundene Primzahl Date lastprimeModified = new Date(); // Zeit Thread searcher; // Hintergrund Thread
public void init() throws ServletException { searcher = new Thread(this); searcher.setPriority(Thread.MIN_PRIORITY); searcher.start(); }
http://www.mindview.net/Books/DownloadSites/
PrimSearcher
public void run() { long candidate = 1000000000000001L;
while (true) { if (isPrime(candidate)) { lastprime = candidate; // aktuelle Primzahl lastprimeModified = new Date(); // Zeit der letzten gefunden
Primzahl } candidate += 2; // keine geraden Primzahlen
try { searcher.sleep(200); // an andere Prozesse denken } catch (InterruptedException ignored) { } }
PrimSearcherprivate static boolean isPrime(long candidate) { // Dividiere die Zahl durch alle ungeraden Zahlen zwischen 3 und sqrt(z) long sqrt = (long) Math.sqrt(candidate); for (long i = 3; i <= sqrt; i += 2) { if (candidate % i == 0) return false; // Ein Faktor gefunden }
return true; //kein Faktor } public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException { res.setContentType("text/plain"); PrintWriter out = res.getWriter(); if (lastprime == 0) { out.println("Still searching for first prime..."); } else { out.println("The last prime discovered was " + lastprime); out.println(" at " + lastprimeModified); } } public void destroy() { searcher.stop();}}
http://archive.coreservlets.com/
package protectedpage;import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import java.util.Properties;
import sun.misc.BASE64Decoder;public class ProtectedPage extends HttpServlet { private Properties passwords; private String passwordFile;
public void init(ServletConfig config) throws ServletException { super.init(config); try { passwordFile = config.getInitParameter("passwordFile"); passwords = new Properties(); passwords.load(new FileInputStream(passwordFile)); } catch(IOException ioe) {} }
Protected Page
Protected Page
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String authorization = request.getHeader("Authorization");
if (authorization == null) {
askForPassword(response);
} else {
Protected Page
String userInfo = authorization.substring(6).trim();
BASE64Decoder decoder = new BASE64Decoder();
String nameAndPassword = new String(decoder.decodeBuffer(userInfo));
int index = nameAndPassword.indexOf(":");
String user = nameAndPassword.substring(0, index);
String password = nameAndPassword.substring(index+1);
String realPassword = passwords.getProperty(user);
if ((realPassword != null) &&
(realPassword.equals(password))) {
String title = "Welcome to the Protected Page";
out.println(ServletUtilities.headWithTitle(title) +
Protected Page
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1 ALIGN=CENTER>" + title + "</H1>\n" +
"Congratulations. You have accessed a\n" +
"highly proprietary company document.\n" +
"Shred or eat all hardcopies before\n" +
"going to bed tonight.\n" +
"</BODY></HTML>");
} else {
askForPassword(response);
}
}
}
Protected Page
private void askForPassword(HttpServletResponse response) {
response.setStatus(response.SC_UNAUTHORIZED); // Ie 401
response.setHeader("WWW-Authenticate",
"BASIC realm=\"privileged-few\"");
}
/** Handle GET and POST identically. */
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
Praktikum
Kundenangaben mit PW Abfrage:
1. http Passwortabfrage
2. Formular mit Passwortabfrage
3. Alle Adressen im Container werden angezeigt.
4. Formular zur Eingabe von weiteren Adressen
(5.) Save & Edit & Delete
3.) alle Daten anzeigen
Ihr Job
1.)
4.) Eingabe2.)
1.) Neues Projekt
2.) HTML Files in Projekt Ordner kopieren und hinzufügen
3. Neues Servlet oder Webanwendung erzeugen
HTML Files zur Webanwendung hinzufügen
web.xml File anpassen
Servlet Class-File Angaben
Servlet Mapping Angaben
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