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Anwendungen Servlet II Formular Auswertung Zähler
Zähler mit Zwischenspeicherung Hintergrund Berechnung Passwort Abfrage
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Auswertung eines Formulars
Get Request Webserver index.html Response Servlet Container processformular Post Request Response
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HTML <FORM> <form method="POST" action="processformular">
<input type="text" name=name size=50 > <input type="submit" > </form> HTML http Request HTML Formular Servlet Auswertung get <form method=“GET" doGet(… post <form method="POST" doPost(…
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Formular erstellen
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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");
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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() {}
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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."); }
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Internet Mehrfach Anfragen
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Daten Inkonsistenz Kein Problem bei lokalen Variablen
Vorsicht bei Instanz Variablen Bsp: 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
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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."); }
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Counter II package 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.");
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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."); }
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Lebenszyklus Initialisierung Antworten auf Anfragen Zerstörung
Persistenz DB Verbindung Information von früheren Transaktionen
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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; }
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InitDestroyCounter 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"); count = Integer.parseInt(initial); return; catch (NumberFormatException ignored) { } // null or non-integer value // Default 0 count = 0;
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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();
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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();
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PrimSearcher http://www.mindview.net/Books/DownloadSites/
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(); }
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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) { }
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PrimSearcher http://archive.coreservlets.com/
private 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();}
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Protected Page 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) {} }
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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 {
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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) +
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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); }
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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);
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Praktikum Kundenangaben mit PW Abfrage: http Passwortabfrage
Formular mit Passwortabfrage Alle Adressen im Container werden angezeigt. Formular zur Eingabe von weiteren Adressen (5.) Save & Edit & Delete
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Ihr Job 1.) 3.) alle Daten anzeigen 2.) 4.) Eingabe
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1.) Neues Projekt
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2.) HTML Files in Projekt Ordner kopieren und hinzufügen
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3. Neues Servlet oder Webanwendung erzeugen
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HTML Files zur Webanwendung hinzufügen
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web.xml File anpassen
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Servlet Class-File Angaben
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Servlet Mapping Angaben
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