which session listner to be impletement

[Samanthi perera]

I need to be loaded the information from database to the system at the start of a ticket purchasing session.
so which type of listner to be impletement?

[Ben Souther]

Why don't you tell us which one you were thinking of using and why.

[Samanthi perera]

here is my requirment.
You are required to design, implement and test a system to simulate the zone/fare management and ticket purchasing system. Your system must be designed using a database to manage zone and fare information and etc. The information should be loaded to the system at the start of a ticket purchasing session. You should set up your database by hand so it has some initial data with a sufficient variety of information in order to fully demonstrate the functionality that you have implemented

[Ben Souther]

Samanthi,

We're happy to help you out with your assignment but we won't do it for you.
Have you read the servlet spec to see which listeners are available?
Did you understand what you read?
Do you have any questions about a particular listener that wasn't answered by reading the spec?

After reading about them, which one do you think best suites your needs?
Why?

[Samanthi perera]

i think sessionbindinglistner is the best.

[Ben Souther]

Why is that?

When does a sessionBindingListener fire?

[Samanthi perera]

when we making a new session it fires.

[Ulf Dittmer]

No, check its javadocs for when it fires.

[Samanthi perera]

it fires when session times out or session invalidate.

[Ben Souther]

Samanthi,

There is a link to the servlet spec in my signature.
It shouldn't take more than 15 minutes to search for the various listeners it provides and read up on them.
That's a lot less time than you've already spent trying to get us to do your work for you.

[Samanthi perera]

still confusing?

[Ben Souther]

Are you asking me if I'm confused or are you telling me that you're confused?

[David Newton]

Ben Souther wrote:Are you asking me if I'm confused or are you telling me that you're confused?

Still confusing?

[Samanthi perera]

i am confused.anyway finally i found the httpsessionlistener is good for my work.

The information should be loaded to the system at the start of a ticket purchasing session

[Ben Souther]

Good luck with your project.

[Samanthi perera]

I need to add a arraylist reference to the servletcontext .
arraylist contain data retrived by database.
then can i do it implimenting httpsessionlistener in a normal java class?
or should i impliment httpsessionlistener in a servlet?

[Ben Souther]

Don't do it from a servlet.

Servlets should only ever have to respond to web requests.
Create a class that implements the listener that you want to use.

[Samanthi perera]

this is my DaoImple class

package dao;

import java.sql.*;
import java.util.ArrayList;

public class ZoneDaoImpl implements ZoneDao {

    public ArrayList<TicketDetails> geTicketDetails() throws Exception {

        Connection c = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        TicketDetails ticket =new TicketDetails();
        ArrayList<TicketDetails> ticketArray = new ArrayList<TicketDetails>();

        try {

            c = getConnection();
            Statement st = c.createStatement();
            ResultSet res = st.executeQuery("SELECT * FROM  tickt");
            while (res.next()) {
               
                
                ticket.setZonetype(res.getString("zonetype"));
                ticket.setZone(res.getString("zone"));
                ticket.setPeak(res.getInt("peak"));
                ticket.setOffpeak(res.getInt("offpeak"));
                ticket.setCash(res.getInt("cash"));
                ticketArray.add(ticket);
                 
            }
        } catch (Exception e) {
            e.printStackTrace();
        }


        return ticketArray;
    }

    public Connection getConnection() {

        Connection conn = null;
        String url = "jdbc:mysql://localhost:3306/";
        String dbName = "zone";
        String driver = "com.mysql.jdbc.Driver";
        String userName = "root";
        String password = "root";

        try {
            Class.forName(driver).newInstance();
            conn = DriverManager.getConnection(url + dbName, userName, password);
            System.out.println("Connected to the database");
           // conn.close();
            System.out.println("Disconnected from database");
            if(conn==null){
                System.out.println("NULLLLLLLLLLLLLLLLLLLLLLLLLLL");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return conn;
    }
}

this is my httpListener class

package listeners;

import dao.TicketDetails;
import dao.ZoneDaoImpl;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class MyHttpSessionListener implements HttpSessionListener {

    static private int activeSessions;

    public static int getActiveSessions() {
        return activeSessions;
    }

    public void sessionCreated(HttpSessionEvent se) {
        activeSessions++;
       
        if(activeSessions==1){
            try {
                getAllData();               
            } catch (Exception ex) {
                Logger.getLogger(MyHttpSessionListener.class.getName()).log(Level.SEVERE, null, ex);
                ex.printStackTrace();
            }
        }
    }

    public void sessionDestroyed(HttpSessionEvent se) {
        activeSessions--;
    }

    private void getAllData() throws Exception {
        ZoneDaoImpl z = new ZoneDaoImpl();
        // z.getConnection();
        ArrayList a = z.geTicketDetails();
        TicketDetails ticket = new TicketDetails();
    }
}

but i need to access this Arraylist fron anywere in my application.
how to archive this?

[Ben Souther]

Why are you only reading from the database when activeSessions == 1?

What is your intent in doing that?

[Samanthi perera]

i change my listener class

package listeners;

import dao.TicketDetails;
import dao.ZoneDaoImpl;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class MyHttpSessionListener implements HttpSessionListener {

    static private int activeSessions;

    public static int getActiveSessions() {
        return activeSessions;
    }

    public void sessionCreated(HttpSessionEvent se) {
        activeSessions++;
       
        if(activeSessions==1){
            try {
                getAllData();

            } catch (Exception ex) {
                Logger.getLogger(MyHttpSessionListener.class.getName()).log(Level.SEVERE, null, ex);
                ex.printStackTrace();
            }
        }
    }

    public void sessionDestroyed(HttpSessionEvent se) {
        activeSessions--;
    }

    private void getAllData() throws Exception {
        ZoneDaoImpl z = new ZoneDaoImpl();
        // z.getConnection();
        ArrayList a = z.geTicketDetails();
        
        MyAllData.setMydata(a);
    }
}

here my static class

package listeners;

import dao.TicketDetails;
import java.util.ArrayList;


public  class  MyAllData{

    public static ArrayList<TicketDetails> getMydata() {
        return mydata;
    }

    public static void setMydata(ArrayList<TicketDetails> mydata) {
        MyAllData.mydata = mydata;
    }

    private static ArrayList<TicketDetails> mydata;

   
}

i use staic method to store arraylist.
is this good design way?

[Ben Souther]

Samanthi perera wrote:
but i need to access this Arraylist fron anywere in my application.
how to archive this?

Hint: What scope object can be seen by all resources in a servlet application?

[Ben Souther]

Storing things in static variables can cause problems in Java web applications.

The servlet spec provides a better place for you to store them.
Again, hint: What scoped object can be seen from all resources in a servlet application?

[Ben Souther]

Ben Souther wrote:Why are you only reading from the database when activeSessions == 1?

What is your intent in doing that?

You still haven't answered this question.

[Samanthi perera]

then only first user loging it get data from database,otherwise each time it gets data from database.
i think it is very resourse consuming.

[Ben Souther]

Is the data going to be the same for all users or is it going to be specific to each user?

The requirements that you posted lead me to believe that the data will be different for each user.
If not then a session listener is not the right tool for this job.

[Samanthi perera]

currently it is same for all users.but there are different data tables which is not same data.
anyway if all data are same what is the listner?

[Ben Souther]

Samanthi perera wrote:currently it is same for all users.but there are different data tables which is not same data.

I'm not sure what that means.
Does your app need to be able to work with different data for each user?

Samanthi perera wrote:
anyway if all data are same what is the listner?

Hint: What scoped object can be seen by all resources in a servlet application?
What other listeners did you see when you were reading the spec earlier?

[Samanthi perera]

I'm not sure what that means.
Does your app need to be able to work with different data for each user?

still i am developing database tables too.
so there is some tables data common for all users,and some tables data is specific for some users.

1)anyway if the all data is common it is better to use contextlistener?
2)if the data is specific for each user httpsessionlistener is good?