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J0 1 Marco Ronchetti - Servlets e JSP.

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Presentation on theme: "J0 1 Marco Ronchetti - Servlets e JSP."— Presentation transcript:

1 J0 1 Marco Ronchetti - ronchet@altavista.it Servlets e JSP

2 J0 2 Marco Ronchetti - ronchet@altavista.it Applets 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 ).

3 J0 3 Marco Ronchetti - ronchet@altavista.it Applets Every applet is implemented by creating a subclass of the Applet class. The hierarchy determines much of what an applet can do and how.

4 J0 4 Marco Ronchetti - ronchet@altavista.it Applet Lifecycle 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()

5 J0 5 Marco Ronchetti - ronchet@altavista.it Applet Lifecycle Whenever its needed, at lower priority init() stop() destroy() start() handleEvent() Multithreading! Actually, more threads are active behind the scenes. paint()

6 J0 6 Marco Ronchetti - ronchet@altavista.it handleEvent() This code is part of the AWT (1.0 Event Model) 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);

7 J0 7 Marco Ronchetti - ronchet@altavista.it handleEvent() 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: return action(evt, evt.arg); case Event.GOT_FOCUS: return gotFocus(evt, evt.arg); case Event.LOST_FOCUS: return lostFocus(evt, evt.arg); } return false; }

8 J0 8 Marco Ronchetti - ronchet@altavista.it Applets-Event handling 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; }

9 J0 9 Marco Ronchetti - ronchet@altavista.it 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 http://java.sun.com/docs/books/tutorial/servlets/overview/index.html http://java.sun.com/docs/books/tutorial/servlets/overview/index.html

10 J0 10 Marco Ronchetti - ronchet@altavista.it Other uses of servlets Allowing collaboration between people. 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.

11 J0 11 Marco Ronchetti - ronchet@altavista.it Applets vs. Servlets AppletServlet Gira:ClientServer Ha un main:NO Estende:java.applet.Appletjavax.servlet.http. HttpServlet GraficaSINO Cuore:handleEvent()service()

12 J0 12 Marco Ronchetti - ronchet@altavista.it Servlet Lifecycle init() destroy() service(HttpServletRequest r, HttpServletResponse p) Chiamato solo la prima volta che la Servlet viene caricato in memoria! doGet() doPost() doXXX() Solo quando serve scaricare dalla memoria! Se la Servlet implements SingleThreadModel non ci saranno esecuzioni simultanee di codice

13 J0 13 Marco Ronchetti - ronchet@altavista.it service() This code is part of the class HttpService protected void service (HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String method = req.getMethod (); if (method.equals ("GET")) { long ifModifiedSince = req.getDateHeader ("If-Modified-Since"); long lastModified = getLastModified (req); maybeSetLastModified (resp, lastModified); if (ifModifiedSince == -1 || lastModified == -1) doGet (req, resp); else { long now = System.currentTimeMillis (); if (now < ifModifiedSince || ifModifiedSince < lastModified) doGet (req, resp); else resp.sendError (HttpServletResponse.SC_NOT_MODIFIED); }

14 J0 14 Marco Ronchetti - ronchet@altavista.it service() } else if (method.equals ("HEAD")) { longlastModified; 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"); }

15 J0 15 Marco Ronchetti - ronchet@altavista.it A taste of servlet programming-1 public class SimpleServlet extends HttpServlet { /** 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";

16 J0 16 Marco Ronchetti - ronchet@altavista.it A taste of servlet programming-2 // set content type and other response header fields first response.setContentType("text/html"); // then write the data of the response out = response.getWriter(); out.println(" "); out.println(title); out.println(" "); out.println(" " + title + " "); out.println(" This is output from SimpleServlet."); out.println(" "); out.close(); }

17 J0 17 Marco Ronchetti - ronchet@altavista.it Esempio: ShowParameters 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(ServletUtilities.headWithTitle(title) + " \n" + " " + title + " \n" + " \n" + " Parameter Name Parameter Value(s)");

18 J0 18 Marco Ronchetti - ronchet@altavista.it Esempio: ShowParameters Enumeration paramNames = request.getParameterNames(); while(paramNames.hasMoreElements()) { String paramName = (String)paramNames.nextElement(); out.print(" " + paramName + "\n "); String[] paramValues = request.getParameterValues(paramName); if (paramValues.length == 1) { String paramValue = paramValues[0]; if (paramValue.length() == 0) out.println(" No Value "); else out.println(paramValue); } else { out.println(" "); for(int i=0; i " +paramValues[i]); } out.println(" "); } out.println(" \n "); }

19 J0 19 Marco Ronchetti - ronchet@altavista.it Esempio: ShowParameters public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }

20 J0 20 Marco Ronchetti - ronchet@altavista.it Esempio: ShowParameters A Sample FORM using POST A Sample FORM using POST Item Number: Quantity: Price Each: First Name: Last Name: Middle Initial: Shipping Address:

21 J0 21 Marco Ronchetti - ronchet@altavista.it Esempio: ShowParameters Credit Card: Visa Master Card American Express Discover Java SmartCard Credit Card Number: Repeat Credit Card Number:

22 J0 22 Marco Ronchetti - ronchet@altavista.it Cookies: perché? Identificazione di un utente in una sessione di e-commerce. Customizzazione di un sito Pubblicità mirata Eliminazione di username e password

23 J0 23 Marco Ronchetti - ronchet@altavista.it 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

24 J0 24 Marco Ronchetti - ronchet@altavista.it Cookies: i metodi public void setMaxAge(int c) public int getMaxAge() Positive value: secondi di vita 0: delete cookie Negative value: finchè dura la sessione del browser

25 J0 25 Marco Ronchetti - ronchet@altavista.it Cookies: i metodi public void setDomain(String c) public String getDomain() public void setPath(int c) public int getPath()

26 J0 26 Marco Ronchetti - ronchet@altavista.it Cookies: esempio Cookie userCookie = new Cookie(user,uid1234); userCookie.setMaxAge(60*60*24*365); response.addCookie(userCookie);

27 J0 27 Marco Ronchetti - ronchet@altavista.it SetCookies 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);

28 J0 28 Marco Ronchetti - ronchet@altavista.it 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) + " \n" +" " + title + " \n" +"There are six cookies associated with this page.\n" + " "); } SetCookies

29 J0 29 Marco Ronchetti - ronchet@altavista.it 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) + " \n" + " " + title + " \n" + " \n" + " Cookie Name\n" + " Cookie Value"); ShowCookies

30 J0 30 Marco Ronchetti - ronchet@altavista.it Cookie[] cookies = request.getCookies(); Cookie cookie; for(int i=0; i { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/570876/1/slides/slide_29.jpg", "name": "J0 30 Marco Ronchetti - ronchet@altavista.it Cookie[] cookies = request.getCookies(); Cookie cookie; for(int i=0; i

31 J0 31 Marco Ronchetti - ronchet@altavista.it 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); Session tracking using cookies

32 J0 32 Marco Ronchetti - ronchet@altavista.it 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); Session tracking API

33 J0 33 Marco Ronchetti - ronchet@altavista.it public void removeValue(String name);//2.1 public void removeAttribute(String name); //2.2 public String[] getValueNames()//2.1 public Enumeration getAttributeNames()//2.2 Session tracking API

34 J0 34 Marco Ronchetti - ronchet@altavista.it 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(); Session tracking API

35 J0 35 Marco Ronchetti - ronchet@altavista.it 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"); ShowSession

36 J0 36 Marco Ronchetti - ronchet@altavista.it 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); ShowSession

37 J0 37 Marco Ronchetti - ronchet@altavista.it out.println(ServletUtilities.headWithTitle(title) + " \n" + " " + heading + " \n" + " Information on Your Session: \n" + " \n" + " Info Type Value\n" + " \n" +" ID\n" +" " + session.getId() + "\n" + " \n" +" Creation Time\n" + " " + new Date(session.getCreationTime()) + "\n" + " \n" +" Time of Last Access\n" + " " +new Date(session.getLastAccessedTime()) + "\n" + " \n" +" Number of Previous Accesses\n" +" " + accessCount + "\n" + " \n" +" "); } ShowSession

38 J0 38 Marco Ronchetti - ronchet@altavista.it /** Handle GET and POST requests identically. */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } ShowSession

39 J0 39 Marco Ronchetti - ronchet@altavista.it Simple.jsp

40 J0 40 Marco Ronchetti - ronchet@altavista.it JSP Lifecycle Browser Servlet generato Servlet compilato Pagina JSP Server Web

41 J0 41 Marco Ronchetti - ronchet@altavista.it Esempi: Direttive

42 J0 42 Marco Ronchetti - ronchet@altavista.it Esempi: Dichiarazioni

43 J0 43 Marco Ronchetti - ronchet@altavista.it Esempi: Sono le Espressioni

44 J0 44 Marco Ronchetti - ronchet@altavista.it Buongiorno Esempio

45 J0 45 Marco Ronchetti - ronchet@altavista.it Esempi: Azioni

46 J0 46 Marco Ronchetti - ronchet@altavista.it Esempi: <% // Get the Employee's Name from the request out.println(" Employee: " + request.getParameter("employee")); // Get the Employee's Title from the request out.println(" Title: " + request.getParameter("title")); %> Scriptlet

47 J0 47 Marco Ronchetti - ronchet@altavista.it outWriter requestHttpServletRequest responseHttpServletResponse sessionHttpSession pagethis nel Servlet applicationservlet.getServletContext area condivisa tra i servlet configServletConfig exceptionsolo nella errorPage pageContext sorgente degli oggetti, raramente usato Oggetti predefiniti

48 J0 48 Marco Ronchetti - ronchet@altavista.it UseRequest <% // Get the User's Name from the request out.println(" Hello: " + request.getParameter("user") + " "); %> request

49 J0 49 Marco Ronchetti - ronchet@altavista.it UseSession <% // 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); } session

50 J0 50 Marco Ronchetti - ronchet@altavista.it else { count = new Integer(count.intValue() + 1); session.setAttribute("COUNT", count); } // Get the User's Name from the request out.println(" Hello you have visited this site: " + count + " times. "); %> session

51 J0 51 Marco Ronchetti - ronchet@altavista.it include file=URL taglib uri=URL prefix=prefisso definisce un meccanismo di estensione delle tag esistenti! Direttive

52 J0 52 Marco Ronchetti - ronchet@altavista.it jsp:useBean jsp:setProperty jsp:getProperty jsp:forward jsp:plugin Azioni


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