Applets, Servlets e JSP
annuncio pubblicitario
J0 1 Marco Ronchetti - [email protected] Applets, Servlets e JSP Marco Ronchetti - [email protected] Applets J0 2 Special Java programs (without a “main”) callable from HTML and executed in a graphic context. They can be executed by: a Java enabled Web Browser; ad-hoc programs (e.g. Sun AppletViewer). Marco Ronchetti - [email protected] Applets J0 3 Every applet is implemented by creating a subclass of the Applet class. The hierarchy determines much of what an applet can do and how. Marco Ronchetti - [email protected] Applet Lifecycle J0 4 An applet can react to major events in the following ways: It can initialize itself. init() It can start running. start() It can draw some graphics. paint() It can respond to user-generated events (Mouse, keyboard, menus…). handleEvent() It can stop running. stop() It can perform a final cleanup, in preparation for being unloaded. destroy() Applet Lifecycle Marco Ronchetti - [email protected] init() start() handleEvent() stop() J0 5 Multithreading! destroy() Whenever it’s needed, at lower priority paint() Actually, more threads are active behind the scenes. handleEvent() Marco Ronchetti - [email protected] This code is part of the AWT (1.0 Event Model) J0 6 public boolean handleEvent(Event evt) { switch (evt.id) { case Event.MOUSE_ENTER: return mouseEnter(evt, evt.x, evt.y); case Event.MOUSE_EXIT: return mouseExit(evt, evt.x, evt.y); case Event.MOUSE_MOVE: return mouseMove(evt, evt.x, evt.y); case Event.MOUSE_DOWN: return mouseDown(evt, evt.x, evt.y); case Event.MOUSE_DRAG: return mouseDrag(evt, evt.x, evt.y); case Event.MOUSE_UP: return mouseUp(evt, evt.x, evt.y); handleEvent() Marco Ronchetti - [email protected] case Event.KEY_PRESS: case Event.KEY_ACTION: return keyDown(evt, evt.key); case Event.KEY_RELEASE: case Event.KEY_ACTION_RELEASE: return keyUp(evt, evt.key); case Event.ACTION_EVENT: case Event.GOT_FOCUS: case Event.LOST_FOCUS: } return false; } J0 7 return action(evt, evt.arg); return gotFocus(evt, evt.arg); return lostFocus(evt, evt.arg); Marco Ronchetti - [email protected] Applets-Event handling J0 8 To react to an event, an applet must override either the appropriate event-specific method or the handleEvent method. For example, adding the following code to the Simple applet makes it respond to mouse clicks. import java.awt.Event; ... public boolean mouseDown(Event event, int x, int y) { addItem("click!... "); return true; } Marco Ronchetti - [email protected] Applets J0 9 Le applets sono uno scheletro di applicazione che gira nello spazio concesso loro da un browser. Il programmatore ha la responsabilita’ di implementare i seguenti metodi (che possono anche essere lasciati vuoti): init() start() stop() destroy() paint() viene eseguito quando la viene eseguito quando la viene eseguito quando la viene eseguito quando la viene eseguito quando la applet viene creata applet (ri)parte applet viene fermata applet viene distrutta applet viene (ri)disegnata NOTA: il programmatore puo’ notificare la necessita’ di ridisegnare la applet tramite la chiamata repaint(). Tuttavia, l’effettivo ridisegno verra’ fatto dal sistema SOLO quando vi saranno risorse disponibili! (vedi Threads). Applet methods - 1a Marco Ronchetti - [email protected] import java.awt.Graphics; import java.util.Date; public class ShowAppletMethods extends java.applet.Applet Date d; int count=0; public void init() { System.out.println((count++)+" Init Executed"); } public void start() { System.out.println((count++)+" Start Executed"); } <HTML><HEAD> <TITLE>Another Applet</TITLE> </HEAD> <BODY> <APPLET CODE="ShowAppletMethods.class" WIDTH=200 HEIGHT=75> </APPLET> </BODY></HTML> public void stop() { System.out.println((count++)+" Stop Executed"); } public void destroy() { System.out.println((count++)+" Destroy Executed"); } public void paint(Graphics g) { System.out.println((count++)+" Paint Executed"); d=new Date(); g.drawString("Time now is "+d.getHours() +":” +d.getMinutes() +":” +d.getSeconds(), 5, 25); } } J0 10 { Marco Ronchetti - [email protected] Elementi Grafici J0 11 import java.awt.*; import java.awt.event.*; public class TestPattern extends java.applet.Applet { int theta = 45; public void paint( Graphics g ) { int Width = size().width; int Height = size().height; int width = Width/2; int height = Height/2; int x = (Width - width)/2; int y = (Height- height)/2; int [] polyx = { 0, Width/2, Width, Width/2 }; int [] polyy = { Height/2, 0, Height/2, Height }; Polygon poly = new Polygon( polyx, polyy, 4 ); g.setColor( Color.black ); g.fillRect( 0, 0, size().width, size().height ); g.setColor( Color.yellow ); g.fillPolygon( poly ); g.setColor( Color.red ); g.fillRect( x, y, width, height ); g.setColor( Color.green ); g.fillOval( x, y, width, height ); g.setColor( Color.blue ); int delta = 90; g.fillArc( x, y, width, height, theta, delta ); g.setColor( Color.white ); g.drawLine( x, y, x+width, x+height ); } public void init() { addMouseListener( new MouseAdapter() { public void mousePressed( MouseEvent e ) { theta= theta+10)%360; repaint(); } } ); } } Marco Ronchetti - [email protected] Metodi grafici di Graphics J0 12 draw3DRect() Draws a highlighted, 3D rectangle drawArc() Draws an arc drawLine() Draws a line drawOval() Draws an oval drawPolygon() Draws a polygon, connecting endpoints drawPolyline() Draws a line connecting a polygon's points drawRect() Draws a rectangle drawRoundRect() Draws a rounded-corner rectangle fill3DRect() Draws a filled, highlighted, 3D rectangle fillArc() Draws a filled arc fillOval() Draws a filled oval fillPolygon() Draws a filled polygon fillRect() Draws a filled rectangle fillRoundRect() Draws a filled, rounded-corner rectangle Text & Fonts Marco Ronchetti - [email protected] import java.awt.Font; import java.awt.FontMetrics; public class ManyFonts extends java.applet.Applet { public void paint(Graphics g) { Font f = new Font("TimesRoman", Font.PLAIN, 18); FontMetrics fm = getFontMetrics(f); g.setFont(f); String s = "This is a plain font"; int xstart = (size().width - fm.stringWidth(s)) / 2; //int ystart = (size().height + fm.getHeight()) / 2; g.drawString(s, xstart, 25); Font fb = new Font("TimesRoman", Font.BOLD, 18); Font fi = new Font("TimesRoman", Font.ITALIC, 18); Font fbi = new Font("TimesRoman", Font.BOLD + Font.ITALIC, 18); g.setFont(fb); g.drawString("This is a bold font", 10, 50); g.setFont(fi); g.drawString("This is an italic font", 10, 75); g.setFont(fbi); g.drawString("This is a bold italic font", 10, 100); } } J0 13 import java.awt.Graphics; Colore import java.awt.Graphics; Marco Ronchetti - [email protected] import java.awt.Color; public class ColorBoxes extends java.applet.Applet { public void paint(Graphics g) { int rval, gval, bval; for (int j = 30; j < (this.size().height -25); j += 30) for (int i = 5; i < (this.size().width -25); i+= 30) { rval = (int)Math.floor(Math.random() * 256); gval = (int)Math.floor(Math.random() * 256); bval = (int)Math.floor(Math.random() * 256); g.setColor(new Color(rval,gval,bval)); g.fillRect(i,j,25,25); g.setColor(Color.black); g.drawRect(i-1,j-1,25,25); } } } J0 14 Applet methods - 2 Marco Ronchetti - [email protected] import java.awt.Graphics; import java.util.Date; J0 15 public class ShowAppletMethods extends java.applet.Applet Date d; int count=0; int seconds; { <HTML><HEAD> <TITLE>Another Applet</TITLE> </HEAD><BODY> <APPLET CODE="ShowAppletMethods.class" WIDTH=200 HEIGHT=75> <PARAM name=secondi value=10> </APPLET> </BODY></HTML> public void init() { System.out.println((count++)+" Init Executed"); seconds=Integer.parseInt(this.getParameter("Secondi")); } public void start() { System.out.println((count++)+" Start Executed"); while (true) { try { public void destroy() { Thread.sleep(seconds*1000); System.out.println((count++)+" Destroy Executed"); } } catch (InterruptedException e) {} public void paint(Graphics g) { System.out.println("==> calling repaint"); System.out.println((count++)+" Paint Executed"); repaint(); d=new Date(); } g.drawString("Time now is ” +d.getHours() +":” } +d.getMinutes() +":” +d.getSeconds(), 5, 25); } public void stop() { } System.out.println((count++)+" Stop Executed"); } Marco Ronchetti - [email protected] Multithreading per la paint() J0 16 La versione precedente del codice non disegna MAI lo schermo! Il problema e’ che il programma ha una singola thread, che e’ sempre occupata: nessuno quindi puo’ eseguire la paint(). La soluzione e’ di creare una nuova thread che faccia il lavoro vero e proprio, lasciando alla applet meno compiti. import java.awt.Graphics; import java.util.Date; Applet methods - 3 Marco Ronchetti - [email protected] public class ShowAppletMethods extends java.applet.Applet Date d; int count=0; simpleThread t; { class simpleThread extends Thread { ShowAppletMethods a; int seconds; simpleThread(ShowAppletMethods a, int s) { this.a=a; seconds=s*1000; } public void init() { System.out.println((count++)+" Init Executed"); int seconds=Integer.parseInt(this.getParameter( "Secondi")); t=new simpleThread(this,seconds); t.start(); } public void run() { public void start() { while (true) { System.out.println((count++)+" Start Executed"); try { } sleep(seconds); public void stop() { } System.out.println((count++)+" Stop Executed"); catch (InterruptedException e) {} } System.out.println("==> THREAD: calling public void destroy() { repaint"); t.stop(); a.repaint(); System.out.println((count++)+" Destroy Executed"); } } } public void paint(Graphics g) { } System.out.println((count++)+" Paint Executed"); d=new Date(); g.drawString("Time now is "+d.getHours() +":” +d.getMinutes() +":” +d.getSeconds(), 5, 25); J0 } 17} Marco Ronchetti - [email protected] Double buffering J0 18 Le animazioni vengono effettuate cancellando l’immagine presente e ridisegnando la nuova. Questo da’ origine ad un fastidioso sfarfallio. Per evitare questo effetto, la nuova immagine viene disegnata in memoria anziche’ a video: quando l’immagine e’ pronta, quella presente a video viene sostituita con la nuova (tecnica di double buffering). La tecnica si basa sulla ridefinizione del metodo “update()” che viene chiamato dalla repaint(), e che a sua volta schedula la paint(). La versione standard di update e’ : public void update(Graphics g) { g.setColor(getBackground()); g.fillRect(0,0,width,height); g.setColor(getForeground()); paint(g); } Animazione con flickering Marco Ronchetti - [email protected] /* simple applet to show very basic startup and animation stuff */ public void run() { while (true) { for (xpos = 5; xpos <= 105; xpos+=4) { repaint(); try { Thread.sleep(100); } catch (InterruptedException e) { } } xpos=5; } } import java.awt.Graphics; import java.awt.Color; public class Checkers extends java.applet.Applet implements Runnable { Thread runner; int xpos; public void update(Graphics g) { paint(g); } public void start() { if (runner == null); { runner = new Thread(this); runner.start(); } } public void paint(Graphics g) { // Draw background g.setColor(Color.black); g.fillRect(0,0,100,100); g.setColor(Color.white); g.fillRect(100,0,100,100); public void stop() { if (runner != null) { runner.stop(); runner = null; } } J0 19 // Draw checker g.setColor(Color.red); g.fillOval(xpos,5,90,90); } } Animazione senza flickering import java.awt.Graphics; import java.awt.Color; import java.awt.Image; Marco Ronchetti - [email protected] public class Checkers2 extends java.applet.Applet implements Runnable { J0 20 Thread runner; int xpos; Image offscreenImg; Graphics offscreenG; g.drawImage(offscreenImg,0,0,this); public void init() { offscreenImg = createImage(this.size().width, this.size().height); offscreenG = offscreenImg.getGraphics(); } public void start() { if (runner == null); { runner = new Thread(this); runner.start(); } } public void stop() { if (runner != null) { runner.stop(); runner = null; } } public void paint(Graphics g) { // Draw background offscreenG.setColor(Color.black); offscreenG.fillRect(0,0,100,100); offscreenG.setColor(Color.white); offscreenG.fillRect(100,0,100,100); // Draw checker offscreenG.setColor(Color.red); offscreenG.fillOval(xpos,5,90,90); } public void destroy() { offscreenG.dispose(); } } NOTA: I contesti grafici non vengono liberati dalla garbage collection, vanno rilasciati esplicitamente! (Vedi destroy) public void run() { while (true) { for (xpos = 5; xpos <= 105; xpos+=4) { repaint(); try { Thread.sleep(100); } catch (InterruptedException e) { } } xpos = 5; } } public void update(Graphics g) { paint(g); } Marco Ronchetti - [email protected] Launching Applets as Apps import java.awt.*; import java.applet.*; public class ShowAppletMethodsAsApplication extends ShowAppletMethods { public static void main(String args[]) { Applet applet=new ShowAppletMethodsAsApplication(); Frame frame=new AppletFrame("ShowAppletMethodsAsApplication",applet,300,300); } } class AppletFrame extends Frame implements ActionListener { public AppletFrame (String title, Applet applet, int width, int height) { //create Frame with specified title // add the applet to the window, super(title); // set window size, show it //add a Menubar this.add("Center",applet); MenuBar menubar=new MenuBar(); this.resize(width,height); Menu file = new Menu("File",true); this.show(); menubar.add(file); //Start the applet MenuItem mExit=new MenuItem("Exit"); applet.init(); file.add(mExit); applet.start(); mExit.addActionListener(this); } this.setMenuBar(menubar); public void actionPerformed(ActionEvent e) System.exit(0); J0 } 21 } Applets and the status line Marco Ronchetti - [email protected] Applets display status lines with the showStatus method. J0 22 showStatus("MyApplet: hello!"); The status line is not usually very prominent, and it can be overwritten by other applets or by the browser. For these reasons, it's best used for incidental, transitory information. Note: Please don't put scrolling text in the status line. Browser users find such status line abuse highly annoying! Marco Ronchetti - [email protected] Applets and HTML text With the AppletContext showDocument method, an applet can tell the browser which URL to show and in which browser window. public void showDocument(java.net.URL url, String targetWindow) For a full example, see J0 23 http://java.sun.com/docs/books/tutorial/applet/appletsonly/browser.html Marco Ronchetti - [email protected] Interaction among applets Applets can find other applets and send messages to them, with the following security restrictions: Many browsers require that the applets originate from the same server. Many browsers require that the applets originate from the same directory on the server (the same code base). The Java API requires that the applets be running on the same page, in the same browser window. For a full example, see J0 24 http://java.sun.com/docs/books/tutorial/applet/appletsonly/iac.html Marco Ronchetti - [email protected] Servlets (JDK 1.2) Servlets are modules that extend Java-enabled web servers. For example, a servlet might be responsible for taking data in an HTML order-entry form and applying the business logic used to update a company's order database. Servlets are to servers what applets are to browsers. Unlike applets, however, servlets have no graphical user interface. For a full tutorial, see J0 25 http://java.sun.com/docs/books/tutorial/servlets/overview/index.html Other uses of servlets Marco Ronchetti - [email protected] Allowing collaboration between people. J0 26 A servlet can handle multiple requests concurrently, and can synchronize requests. This allows servlets to support systems such as on-line conferencing. Forwarding requests. Servlets can forward requests to other servers and servlets. Thus servlets can be used to balance load among several servers that mirror the same content, and to partition a single logical service over several servers, according to task type or organizational boundaries. Marco Ronchetti - [email protected] Applets vs. Servlets J0 27 Applet Servlet Gira: Client Server Ha un main: NO NO Estende: java.applet.Applet Grafica SI javax.servlet.http. HttpServlet NO Cuore: handleEvent() service() Marco Ronchetti - [email protected] Servlet Lifecycle J0 28 Chiamato solo la prima volta che la Servlet viene caricato in memoria! init() doXXX() service(HttpServletRequest r, HttpServletResponse p) doGet() doPost() Se la Servlet implements SingleThreadModel non ci saranno esecuzioni simultanee di codice destroy() Solo quando serve scaricare dalla memoria! service() Marco Ronchetti - [email protected] This code is part of the class HttpService J0 29 protected void service (HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String method = req.getMethod (); if (method.equals ("GET")) { long ifModifiedSince; long lastModified; long now; ifModifiedSince = req.getDateHeader ("If-Modified-Since"); lastModified = getLastModified (req); maybeSetLastModified (resp, lastModified); if (ifModifiedSince == -1 || lastModified == -1) doGet (req, resp); else { now = System.currentTimeMillis (); if (now < ifModifiedSince || ifModifiedSince < lastModified) doGet (req, resp); else resp.sendError (HttpServletResponse.SC_NOT_MODIFIED); } service() Marco Ronchetti - [email protected] } else if (method.equals ("HEAD")) { long lastModified; lastModified = getLastModified (req); maybeSetLastModified (resp, lastModified); doHead (req, resp); } else if (method.equals ("POST")) { doPost (req, resp); } else if (method.equals ("PUT")) { doPut(req, resp); } else if (method.equals ("DELETE")) { doDelete(req, resp); } else if (method.equals ("OPTIONS")) { doOptions(req,resp); } else if (method.equals ("TRACE")) { doTrace(req,resp); } else { resp.sendError (HttpServletResponse.SC_NOT_IMPLEMENTED, "Method '" + method + "' is not defined in RFC 2068"); } J0 30 } A taste of servlet programming-1 Marco Ronchetti - [email protected] public class SimpleServlet extends HttpServlet { J0 31 /** Handle the HTTP GET method by building a simple web page. */ public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out; String title = "Simple Servlet Output"; A taste of servlet programming-2 // set content type and other response header fields first Marco Ronchetti - [email protected] response.setContentType("text/html"); // then write the data of the response out = response.getWriter(); out.println("<HTML><HEAD><TITLE>"); out.println(title); out.println("</TITLE></HEAD><BODY>"); out.println("<H1>" + title + "</H1>"); out.println("<P>This is output from SimpleServlet."); out.println("</BODY></HTML>"); out.close(); } J0 32 } Marco Ronchetti - [email protected] Esempio: ShowParameters J0 33 package coreservlets; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; public class ShowParameters extends HttpServlet { public void doGet(HttpServletRequest request HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Reading All Request Parameters"; out.println(“<HEAD><TITLE>”+title + “</TITLE> </HEAD>”)+ "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<H1 ALIGN=CENTER>" + title + "</H1>\n" + "<TABLE BORDER=1 ALIGN=CENTER>\n" + "<TR BGCOLOR=\"#FFAD00\">\n" + "<TH>Parameter Name<TH>Parameter Value(s)"); Marco Ronchetti - [email protected] Esempio: ShowParameters J0 34 Enumeration paramNames = request.getParameterNames(); while(paramNames.hasMoreElements()) { String paramName = (String)paramNames.nextElement(); out.print("<TR><TD>" + paramName + "\n<TD>"); String[] paramValues = request.getParameterValues(paramName); if (paramValues.length == 1) { String paramValue = paramValues[0]; if (paramValue.length() == 0) out.println("<I>No Value</I>"); else out.println(paramValue); } else { out.println("<UL>"); for(int i=0; i<paramValues.length; i++) {out.println("<LI>" +paramValues[i]); } out.println("</UL>"); } } out.println("</TABLE>\n</BODY></HTML>"); } Marco Ronchetti - [email protected] Esempio: ShowParameters J0 35 public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } Marco Ronchetti - [email protected] Esempio: ShowParameters J0 36 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> <TITLE>A Sample FORM using POST </TITLE> </HEAD> <BODY BGCOLOR="#FDF5E6"> <H1 ALIGN="CENTER">A Sample FORM using POST</H1> <FORM ACTION="/servlet/coreservlets.ShowParameters“ METHOD="POST”> Item Number: <INPUT TYPE="TEXT" NAME="itemNum"><BR> Quantity: <INPUT TYPE="TEXT" NAME="quantity"><BR> Price Each: <INPUT TYPE="TEXT" NAME="price" VALUE="$"><BR> <HR> First Name: <INPUT TYPE="TEXT" NAME="firstName"><BR> Last Name: <INPUT TYPE="TEXT" NAME="lastName"><BR> Middle Initial: <INPUT TYPE="TEXT" NAME="initial"><BR> Shipping Address: <TEXTAREA NAME="address" ROWS=3 COLS=40></TEXTAREA><BR> Marco Ronchetti - [email protected] Esempio: ShowParameters J0 37 Credit Card:<BR> &nbsp;&nbsp;<INPUT TYPE="RADIO" NAME="cardType“ VALUE="Visa">Visa<BR> &nbsp;&nbsp;<INPUT TYPE="RADIO" NAME="cardType" VALUE="Master Card">Master Card<BR> &nbsp;&nbsp;<INPUT TYPE="RADIO" NAME="cardType" VALUE="Amex">American Express<BR> &nbsp;&nbsp;<INPUT TYPE="RADIO" NAME="cardType“ VALUE="Discover">Discover<BR> &nbsp;&nbsp;<INPUT TYPE="RADIO" NAME="cardType" VALUE="Java SmartCard">Java SmartCard<BR> Credit Card Number: <INPUT TYPE="PASSWORD" NAME="cardNum"><BR> Repeat Credit Card Number: <INPUT TYPE="PASSWORD" NAME="cardNum"><BR><BR> <CENTER><INPUT TYPE="SUBMIT" VALUE="Submit Order"></CENTER> </FORM> </BODY> </HTML> Marco Ronchetti - [email protected] Cookies: perché? J0 38 Identificazione di un utente in una sessione di e-commerce. Customizzazione di un sito Pubblicità mirata Eliminazione di username e password Marco Ronchetti - [email protected] Cookies: i metodi public void setComment(String c) public String getComment() public void setVersion(int c) public int getVersion () Version 0: Netscape standard Version 1: RFC 2109 J0 39 Marco Ronchetti - [email protected] Cookies: i metodi J0 40 public void setMaxAge(int c) public int getMaxAge() Positive value: secondi di vita 0: delete cookie Negative value: finchè dura la sessione del browser Marco Ronchetti - [email protected] Cookies: i metodi J0 41 public void setDomain(String c) public String getDomain() public void setPath(int c) public int getPath() Marco Ronchetti - [email protected] Cookies: esempio J0 42 Cookie userCookie = new Cookie(“user”,”uid1234”); userCookie.setMaxAge(60*60*24*365); response.addCookie(userCookie); Marco Ronchetti - [email protected] SetCookies J0 43 import java.io.*; import javax.servlet.*; import javax.servlet.http.*; /** Sets six cookies: three that apply only to the current session * (regardless of how long that session lasts) and three that persist for an hour * (regardless of whether the browser is restarted). */ public class SetCookies extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { for(int i=0; i<3; i++) { // Default maxAge is -1, indicating cookie // applies only to current browsing session. Cookie cookie = new Cookie("Session-Cookie-" + i, "Cookie-Value-S" + i); response.addCookie(cookie); Marco Ronchetti - [email protected] SetCookies J0 44 cookie = new Cookie("Persistent-Cookie-" + i,"Cookie-Value-P" + i); // Cookie is valid for an hour, regardless of whether // user quits browser, reboots computer, or whatever. cookie.setMaxAge(3600); response.addCookie(cookie); } response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Setting Cookies"; out.println (ServletUtilities.headWithTitle(title) + "<BODY BGCOLOR=\"#FDF5E6\">\n" +"<H1 ALIGN=\"CENTER\">" + title + "</H1>\n" +"There are six cookies associated with this page.\n" + "</BODY></HTML>"); } } Marco Ronchetti - [email protected] ShowCookies J0 45 import java.io.*; import javax.servlet.*; import javax.servlet.http.*; /** Creates a table of the cookies associated with the current page. */ public class ShowCookies extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Active Cookies"; out.println(ServletUtilities.headWithTitle(title) + "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<H1 ALIGN=\"CENTER\">" + title + "</H1>\n" + "<TABLE BORDER=1 ALIGN=\"CENTER\">\n" + "<TR BGCOLOR=\"#FFAD00\">\n" + " <TH>Cookie Name\n" + " <TH>Cookie Value"); Marco Ronchetti - [email protected] ShowCookies J0 46 Cookie[] cookies = request.getCookies(); Cookie cookie; for(int i=0; i<cookies.length; i++) { cookie = cookies[i]; out.println("<TR>\n" + " <TD>" + cookie.getName() + "\n" + " <TD>" + cookie.getValue()); } out.println("</TABLE></BODY></HTML>"); } } Marco Ronchetti - [email protected] Session tracking using cookies J0 47 String sessionID = makeUniqueString(); Hashtable sessionInfo = new Hashtable(); Hashtable globalTable = getTableStoringSession(); globalTable.put(sessionID,sessionInfo); Cookie sessionCookie=new Cookie(“SessionID”,sessionID); sessionCookie.setPath(“/”); response.addCookie(sessionCookie); Marco Ronchetti - [email protected] Session tracking API J0 48 HttpSession session = request.getSession(true); ShoppingCart cart = (ShoppingCart)session.getValue(“carrello”); // 2.1 // 2.2 (ShoppingCart)session.getAttribute(“carrello”); if (cart==null) { cart=new ShoppingCart(); session.putValue(“carrello”,cart); //2.1 //2.2 session.putValue(“carrello”,cart); } doSomeThingWith(cart); Marco Ronchetti - [email protected] Session tracking API J0 49 public void removeValue(String name); //2.1 public void removeAttribute(String name); //2.2 public String[] getValueNames() public Enumeration getAttributeNames() //2.1 //2.2 Marco Ronchetti - [email protected] Session tracking API J0 50 public long getCreationTime(); public long getLastAccessdTime(); Secondi dal 1.1.1970, mezzanotte public void removeAttribute(String name); public int getMaxInactiveInterval(); public void setMaxInactiveInterval(int sec); public void invalidate(); Marco Ronchetti - [email protected] ShowSession J0 51 import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.net.*; import java.util.*; /** Simple example of session tracking. */ public class ShowSession extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Session Tracking Example"; HttpSession session = request.getSession(true); String heading; // Use getAttribute instead of getValue in version 2.2. Integer accessCount = (Integer)session.getValue("accessCount"); Marco Ronchetti - [email protected] ShowSession J0 52 if (accessCount == null) { accessCount = new Integer(0); heading = "Welcome Newcomer"; } else { heading = "Welcome Back"; accessCount = new Integer(accessCount.intValue() + 1); } // Use setAttribute instead of putValue in version 2.2. session.putValue("accessCount", accessCount); Marco Ronchetti - [email protected] ShowSession J0 53 out.println(ServletUtilities.headWithTitle(title) + "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<H1 ALIGN=\"CENTER\">" + heading + "</H1>\n" + "<H2>Information on Your Session:</H2>\n" + "<TABLE BORDER=1 ALIGN=\"CENTER\">\n" + "<TR BGCOLOR=\"#FFAD00\">\n" + " <TH>Info Type<TH>Value\n" + "<TR>\n" +" <TD>ID\n" +" <TD>" + session.getId() + "\n" + "<TR>\n" +" <TD>Creation Time\n" + " <TD>" + new Date(session.getCreationTime()) + "\n" + "<TR>\n" +" <TD>Time of Last Access\n" + " <TD>" +new Date(session.getLastAccessedTime()) + "\n" + "<TR>\n" +" <TD>Number of Previous Accesses\n" +" <TD>" + accessCount + "\n" + "</TABLE>\n" +"</BODY></HTML>"); } ShowSession Marco Ronchetti - [email protected] /** Handle GET and POST requests identically. */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } J0 54 Marco Ronchetti - [email protected] Simple.jsp J0 55 <html> <body> <% out.println(“Hello World”); %> </body> </html> Marco Ronchetti - [email protected] JSP Lifecycle Server Web Pagina JSP Browser Servlet generato Servlet compilato J0 56 Direttive Marco Ronchetti - [email protected] <%@ DIRETTIVA {attributo=valore} %> J0 57 Esempi: <%@ page language=java %> <%@ page import=java.awt.*,java.util.* session=true %> Dichiarazioni Marco Ronchetti - [email protected] <%! DICHIARAZIONE %> J0 58 Esempi: <%! String nome=pippo %> <%! public String getName() {return nome} %> Espressioni Marco Ronchetti - [email protected] <%= ESPRESSIONE%> J0 59 Esempi: <%= getName() %> <%@ page import=java.util.* %> Sono le <%= new Date().toString(); %> Marco Ronchetti - [email protected] Esempio J0 60 <html><body> <%! String nome=pippo %> <%! public String getName() {return nome} %> <H1> Buongiorno <%= getName() %> </H1> </body></html> Marco Ronchetti - [email protected] Azioni <jsp:AZIONE> Esempi: <jsp:forward page=URL> <jsp:include page=URL flush=true> <jsp:useBean> J0 61 Scriptlet Marco Ronchetti - [email protected] <% SCRIPTLET %> J0 62 Esempi: <% z=z+1; %> <% // Get the Employee's Name from the request out.println("<b>Employee: </b>" + request.getParameter("employee")); // Get the Employee's Title from the request out.println("<br><b>Title: </b>" + request.getParameter("title")); %> Marco Ronchetti - [email protected] Oggetti predefiniti J0 63 out request response session page application Writer HttpServletRequest HttpServletResponse HttpSession this nel Servlet servlet.getServletContext area condivisa tra i servlet config exception pageContext ServletConfig solo nella errorPage sorgente degli oggetti, raramente usato Marco Ronchetti - [email protected] request J0 64 <%@ page errorPage="errorpage.jsp" %> <html> <head> <title>UseRequest</title> </head> <body> <% // Get the User's Name from the request out.println("<b>Hello: " + request.getParameter("user") + "</b>"); %> </body> </html> session Marco Ronchetti - [email protected] <%@ page errorPage="errorpage.jsp" %> J0 65 <html> <head> <title>UseSession</title> </head> <body> <% // Try and get the current count from the session Integer count = (Integer)session.getAttribute("COUNT"); // If COUNT is not found, create it and add it to the session if ( count == null ) { count = new Integer(1); session.setAttribute("COUNT", count); } Marco Ronchetti - [email protected] session J0 66 else { count = new Integer(count.intValue() + 1); session.setAttribute("COUNT", count); } // Get the User's Name from the request out.println("<b>Hello you have visited this site: " + count + " times.</b>"); %> </body> </html> Marco Ronchetti - [email protected] Direttive J0 67 include file=“URL” taglib uri=“URL” prefix=“prefisso” definisce un meccanismo di estensione delle tag esistenti! Marco Ronchetti - [email protected] Azioni jsp:useBean jsp:setProperty jsp:getProperty jsp:forward jsp:plugin J0 68
