Java Servlets

Java Servlets Svetlin Nakov Borislava Spasova

Contents ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Contents (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Java Servlets Technology Overview

What is a Java Servlet? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What is a Java Servlet? (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Servlet Services ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Why Use Servlets? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Why Use Servlets? (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Time Servlet – Example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Deploying Servlets on Eclipse IDE ,[object Object]

Deploying Servlets on Eclipse IDE (2) ,[object Object]

Java Servlets Technical Architecture

Servlets Architecture ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Servlets Architecture (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Servlets Architecture (3) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Servlets API ,[object Object],[object Object],[object Object],[object Object],HttpServletRequest.getParameter( String ) ServletConfig.getInitParameter () HttpServletRequest.getHeader( String )

Servlets API (2) ,[object Object],[object Object],[object Object],[object Object],HttpServletResponse.setHeader (<name>, <value>) / HttpServletResponse.setContentType( String ) HttpServletResponse.getWriter() HttpServletResponse . getOutputStream() HttpServletResponse.sendRedirect()

Servlets Life-Cycle ,[object Object],[object Object],[object Object],init() ...() service() doGet() doPost() doDelete() destroy() doPut() New Destroyed Running

The init() Method ,[object Object],[object Object],[object Object],[object Object],[object Object]

The service() Method ,[object Object],[object Object],[object Object],[object Object]

The destroy() Method ,[object Object],[object Object],[object Object],[object Object],[object Object]

Processing Parameters – Hello Servlet ,[object Object],[object Object],[object Object],<form method=" GET or POST " action=" the servlet "> <input type="text" name=" user_name "> </form> String n ame = r equest.getParameter("user_name");

Hello Servlet – Example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],HelloForm.html import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloServlet extends HttpServlet { Hello Servlet . java

Hello Servlet – Example public void doGet(HttpServletRequest r equest, HttpServletResponse r esponse) throws ServletException, IOException { r esponse.setContentType("text/html"); ServletOutputStream out = r esponse.getOutputStream(); String userName = r equest.getParameter("user_name"); out.println("<html> <head> "); out.println("<title>Hello Servlet</title>"); out.println("</head><body>"); out.println("<h1>Hello, " + userName + "</h1>"); out.println("</body></html>"); } Hello Servlet . java

Creating The Form in Eclipse IDE ,[object Object]

Creating New Servlet in Eclipse IDE ,[object Object]

Hello Servlet – HTTP Request ,[object Object],[object Object],GET /FirstWebApp/HelloServlet?user_name=Nakov HTTP/1.1 Accept: image/gif, image/x-xbitmap, image/jpeg,image/pjpeg, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-shockwave-flash, */* Accept-Language: bg Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; Q312461) Host: nakov:808 4 Connection: Keep-Alive

Hello Servlet – HTTP Response ,[object Object],[object Object],HTTP/1.1 200 OK Content-Length: 100 Date: Fri, 26 Mar 200 6 10:06:28 GMT Server: Apache-Coyote/1.1 <html><head> <title>Hello Servlet</title> </head><body> <h1>Hello, Nakov</h1> </body></html>

Image Counter Servlet ,[object Object],[object Object],[object Object],[object Object],[object Object]

Image Counter Servlet (2) import javax.servlet.*; import javax.servlet.http.*; ... public class ImageCounterServlet extends HttpServlet { private String mStartDate; private int mVisitCounter; public void init() { mStartDate = (new Date()).toString(); mVisitCounter = 0; } public BufferedImage createImage(String msg) { ... }

Image Counter Servlet (3) public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { String msg; synchronized(this) { mVisitCounter++; msg = "" + mVisitCounter + " visits since " + mStartDate; } BufferedImage image = createImage(msg); response.setContentType("image/jpeg"); OutputStream out = response.getOutputStream(); // Encode the image in JPEG format and // write the image to the output stream } }

Image Counter Servlet in Action

What is a Session? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Sessions in Servlets ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The Sessions API ,[object Object],[object Object],[object Object],[object Object],[object Object]

Getting The Session Object ,[object Object],[object Object],[object Object],[object Object],[object Object],HttpSession session = request.getSession();

Behind T he Scenes ,[object Object],[object Object],[object Object],[object Object],[object Object]

Extracting Data From The Session ,[object Object],[object Object],[object Object],[object Object],[object Object],Integer accessCount = (Integer) session.getAttribute("accessCount"); Enumeration attributes = request.getAttributeNames();

Storing Data In The Session ,[object Object],[object Object],HttpSession session = request.getSession(); session.setAttribute("name", "Svetlin Nakov"); session. remove Attribute("name");

Getting Additional Session Information ,[object Object],[object Object],[object Object],[object Object],public boolean isNew(); public String getId(); public long getLastAccessedTime(); public long getCreationTime();

Session Timeout ,[object Object],[object Object],[object Object],[object Object],public int getMaxInactiveInterval(); public void setMaxInactiveInterval (int seconds) ;

Terminating Sessions ,[object Object],[object Object],[object Object],[object Object],public void invalidate() ;

Login / Logout – Example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Login Form <html> <head><title>Login</title></head> <body> <form method="POST" action="LoginServlet"> Please login:<br> Username: <input type="text" name="username"><br> Password: <input type="password" name="password"><br> <input type="submit" value="Login"> </form> </body> </html> LoginForm.html

Login Servlet public class LoginServlet extends HttpServlet { public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException { String username = req.getParameter("username"); String password = req.getParameter("password"); PrintWriter out = resp.getWriter(); if (isLoginValid(username, password)) { HttpSession session = req.getSession(); session.setAttribute("USER", username); response.sendRedirect("MainServlet"); } else { response.sendRedirect("InvalidLogin.html"); } } } Login Servlet . java

Main Servlet public class MainServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse resp) throws ServletException, IOException { HttpSession session = request.getSession(); String userName = (String) s ession.getAttribute("USER"); if (userName != null) { response.setContentType("text/html"); ServletOutputStream out = resp.getOutputStream(); out.println("<html> <body><h1> "); out.println("Hello, " + userName + "! "); out.println(" </h1> </body></html>"); } else { response.sendRedirect("LoginForm.html"); } } } MainServlet.java

Logout Servlet public class LogoutServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); session.invalidate(); response.setContentType("text/html"); ServletOutputStream out = response.getOutputStream(); out.println("<html><head>"); out.println("<title>Logout</title></head>"); out.println("<body>"); out.println("<h1>Logout successfull.</h1>"); out.println("</body></html>"); } } LogoutServlet.java

Invalid Login Page <html> <head> <title>Error</title> </head> <body> <h1>Invalid login!</h1> Please <a href="LoginForm.html">try again</a>. </body> </html> InvalidLogin.html

The Browser's Cache Problems ,[object Object],[object Object],[object Object],[object Object],response.setHeader("Pragma", "No-cache"); response.setDateHeader("Expires", 0); response.setHeader("Cache-Control", "no-cache");

Problems ,[object Object],[object Object],[object Object],[object Object]

Homework ,[object Object],[object Object],[object Object],[object Object],[object Object]

Homework (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Java Servlets

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