Java Tutorial/Servlet/Session

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Get Set SessionAttributes in Servlet

import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyServlet extends HttpServlet {
   
  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    res.setContentType("text/html");
    PrintWriter out = res.getWriter();
    HttpSession session = req.getSession();
    Integer count = (Integer)session.getAttribute("tracker.count");
    if (count == null)
      count = new Integer(1);
    else
      count = new Integer(count.intValue() + 1);
    session.setAttribute("tracker.count", count);
    out.println("<HTML><HEAD><TITLE>SessionTracker</TITLE></HEAD>");
    out.println("<BODY><H1>Session Tracking Demo</H1>");
    out.println("You"ve visited this page " + count +
      ((count.intValue() == 1) ? " time." : " times."));
    out.println("<P>");
    out.println("<H2>Here is your session data:</H2>");
    Enumeration e = session.getAttributeNames();
    while (e.hasMoreElements()) {
      String name = (String) e.nextElement();
      out.println(name + ": " + session.getAttribute(name) + "<BR>");
    }
    out.println("</BODY></HTML>");
  }
}





Get Set Session Value in a Servlet

import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyServlet extends HttpServlet {
   
    public void doGet(HttpServletRequest request, HttpServletResponse response) 
        throws ServletException, IOException 
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        HttpSession session = request.getSession(true);
        Integer counter2 = (Integer) getServletContext().getAttribute ("counter2");
        if (counter2 == null) {
            counter2 = new Integer(1);
        } else {
            counter2 = new Integer(counter2.intValue() + 1);
        }
        getServletContext().setAttribute("counter2", counter2);
        Integer counter = (Integer) session.getAttribute("counter");
        if (counter == null) {
            counter = new Integer(1);
        } else {
            counter = new Integer(counter.intValue() + 1);
        } 
        session.setAttribute("counter", counter);
        out.println("<HTML>");
        out.println("<HEAD>");
        out.println("<TITLE>");
        out.println("Using Contexts");
        out.println("</TITLE>");
        out.println("</HEAD>");
        out.println("<BODY>");
        out.println("<H1>Using Contexts</H1>");
        out.println("Welcome! You have been here " + counter + " times.<BR>");
        out.println("Total page accesses: " + counter2 + "<BR>");
        if(session.isNew()){
            out.println("This is a new session.<BR>");
        } else {
            out.println("This is not a new session.<BR>");
        }
        out.println("The session ID: " + session.getId() + "<BR>");
        out.println("Last time accessed: " + new Date(session.getLastAccessedTime()) + "<BR>"); 
        out.println("Creation time: " + new Date(session.getCreationTime()) + "<BR>");
        out.println("Timeout length: " + session.getMaxInactiveInterval() + " seconds<BR>");
        out.println("</BODY>");
        out.println("</HTML>");
    } 
}





Servlet Session Check

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.text.DateFormat;
public class MyServlet extends HttpServlet {
   
 public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, java.io.IOException {
        
    HttpSession session = request.getSession(false);
    if (session == null){
        response.sendRedirect("/dbproj/login.jsp");
      } else {
        response.sendRedirect("/dbproj/menu.jsp");
    }
       
     
  } 
}





Servlet Session Creation Last Access Time

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.text.DateFormat;
public class MyServlet extends HttpServlet {
   
 public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, java.io.IOException {
        
        response.setContentType("text/html");
        java.io.PrintWriter out = response.getWriter();
        HttpSession session = request.getSession();
        Date creationTime = new Date(session.getCreationTime() );
        Date lastAccessed = new Date(session.getLastAccessedTime());
        Date now = new Date();
        DateFormat formatter = DateFormat.getDateTimeInstance(DateFormat.MEDIUM,DateFormat.MEDIUM);
        
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Displaying the Session Creation and Last-Accessed Time</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h2>Session Creation and Last-Accessed Time</h2>");
        out.println("The time and date now is: " + formatter.format(now) + "<br><br>");
        out.println("The session creation time: HttpSession.getCreationTime( ): " + formatter.format(creationTime) + "<br><br>");
        out.println("The last time the session was accessed: HttpSession.getLastAccessedTime( ): " + formatter.format(lastAccessed) );
        out.println("</body>");
        out.println("</html>");
        
        
    }
}





Servlet Session Info

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
public class MyServlet extends HttpServlet {
   
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, java.io.IOException {
        
        response.setContentType("text/html");
        java.io.PrintWriter out = response.getWriter();
        HttpSession session = request.getSession();
        
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Simple Session Tracker</title>");
        out.println("</head>");
        out.println("<body>");
        
        out.println("<h2>Session Info</h2>");
        out.println("session Id: " + session.getId() + "<br><br>");
        out.println( "The SESSION TIMEOUT period is " + session.getMaxInactiveInterval() + " seconds.<br><br>");
        out.println( "Now changing it to 20 minutes.<br><br>");
        session.setMaxInactiveInterval(20 * 60);
        out.println("The SESSION TIMEOUT period is now " + session.getMaxInactiveInterval()  + " seconds.");
        
        out.println("</body>");
        out.println("</html>");
        
    } 
    /** Handles the HTTP <code>POST</code> method.
    * @param request servlet request
    * @param response servlet response
    */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, java.io.IOException {
       
    doGet(request,response);
    }

}





Servlet Session Max Inactive Interval

import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyServlet extends HttpServlet {
   
  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    res.setContentType("text/html");
    PrintWriter out = res.getWriter();
    // Get the current session object, create one if necessary
    HttpSession session = req.getSession();
    out.println("<HTML><HEAD><TITLE>SessionTimer</TITLE></HEAD>");
    out.println("<BODY><H1>Session Timer</H1>");
    // Display the previous timeout
    out.println("The previous timeout was " +
                session.getMaxInactiveInterval());
    out.println("<BR>");
    // Set the new timeout
    session.setMaxInactiveInterval(2*60*60);  // two hours
    // Display the new timeout
    out.println("The newly assigned timeout is " +
                session.getMaxInactiveInterval());
    out.println("</BODY></HTML>");
  }
}





Servlet Session Snoop

import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyServlet extends HttpServlet {
   
  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    res.setContentType("text/html");
    PrintWriter out = res.getWriter();
    HttpSession session = req.getSession();
    Integer count = (Integer)session.getAttribute("snoop.count");
    if (count == null)
      count = new Integer(1);
    else
      count = new Integer(count.intValue() + 1);
    session.setAttribute("snoop.count", count);
    out.println("<HTML><HEAD><TITLE>SessionSnoop</TITLE></HEAD>");
    out.println("<BODY><H1>Session Snoop</H1>");
    out.println("You"ve visited this page " + count +
      ((count.intValue() == 1) ? " time." : " times."));
    out.println("<P>");
    out.println("<H3>Here is your saved session data:</H3>");
    Enumeration e = session.getAttributeNames();
    while (e.hasMoreElements()) {
      String name = (String) e.nextElement();
      out.println(name + ": " + session.getAttribute(name) + "<BR>");
    }
    out.println("<H3>Here are some vital stats on your session:</H3>");
    out.println("Session id: " + session.getId() +
                " <I>(keep it secret)</I><BR>");
    out.println("New session: " + session.isNew() + "<BR>");
    out.println("Timeout: " + session.getMaxInactiveInterval());
    out.println("<I>(" + session.getMaxInactiveInterval() / 60 + 
                " minutes)</I><BR>");
    out.println("Creation time: " + session.getCreationTime());
    out.println("<I>(" + new Date(session.getCreationTime()) + ")</I><BR>");
    out.println("Last access time: " + session.getLastAccessedTime());
    out.println("<I>(" + new Date(session.getLastAccessedTime()) +
                ")</I><BR>");
    out.println("Requested session ID from cookie: " +
                req.isRequestedSessionIdFromCookie() + "<BR>");
    out.println("Requested session ID from URL: " +
                req.isRequestedSessionIdFromURL() + "<BR>");
    out.println("Requested session ID valid: " +
                 req.isRequestedSessionIdValid() + "<BR>");
    out.println("<H3>Test URL Rewriting</H3>");
    out.println("Click 



==  Session Events ==






   
  <!-- start source code -->
   
    <source lang="java">
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;
public class Binder extends HttpServlet {
  public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException,
      IOException {
    resp.setContentType("text/html");
    PrintWriter out = resp.getWriter();
    HttpSession session = req.getSession(true);
    SessionObject o = new SessionObject(getServletContext());
    session.setAttribute("Binder.object", o);
    out.println("<html>");
    out.println("<head>");
    out.println("<title>Session Binder</title>");
    out.println("</head>");
    out.println("<body>");
    out.println("Object bound to session " + session.getId());
    out.println("</body>");
    out.println("</html>");
    out.flush();
  }
}
class SessionObject implements HttpSessionBindingListener {
  ServletContext context;
  public SessionObject(ServletContext context) {
    this.context = context;
  }
  public void valueBound(HttpSessionBindingEvent event) {
    context.log("" + (new java.util.Date()) + " Binding " + event.getName() + " to session "
        + event.getSession().getId());
  }
  public void valueUnbound(HttpSessionBindingEvent event) {
    context.log("" + (new java.util.Date()) + " Unbinding " + event.getName() + " from session "
        + event.getSession().getId());
  }
}





use the Servlet API to manage session information

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class Counter extends HttpServlet {
  static final String COUNTER_KEY = "Counter.count";
  public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException,
      IOException {
    HttpSession session = req.getSession(true);
    resp.setContentType("text/html");
    PrintWriter out = resp.getWriter();
    int count = 1;
    Integer i = (Integer) session.getAttribute(COUNTER_KEY);
    if (i != null) {
      count = i.intValue() + 1;
    }
    session.setAttribute(COUNTER_KEY, new Integer(count));
    out.println("<html>");
    out.println("<head>");
    out.println("<title>Session Counter</title>");
    out.println("</head>");
    out.println("<body>");
    out.println("Your session ID is <b>" + session.getId());
    out.println("</b> and you have hit this page <b>" + count
        + "</b> time(s) during this browser session");
    out.println("<form method=GET action=\"" + req.getRequestURI() + "\">");
    out.println("<input type=submit " + "value=\"Hit page again\">");
    out.println("</form>");
    out.println("</body>");
    out.println("</html>");
    out.flush();
  }
}


Источник — «http://jexp.ru/index.php?title=Java_Tutorial/Servlet/Session&oldid=4904»