How to Server Push when Event has occured?

Hello!

Does anyone got a better solution for this?

What I need to create is a servlet that uses Server side Push/Server sid Reload. When something happens a page should be reloaded.

Suppose that you got a visit counter at a page in a browser and if that counter is updated from an other page in an other browser all other page in all browsers with that counter needs to be updated.

I have created a ugly hack that produce this, but I'm not satisfied with it. My hack does a file access every second and I do not want that.

What I would like is some Listener that listens if perhaps the file is changed or some other Event has occur on the server side but I do not know if that is possible.

Below is my ugly hack divided in 2 Servlets. My FileManager just reads a number from a file, nothing magic.

So if any one got a nice solution please let me know!

BTW Server side Push doesn't work in Internet Explorer I use a old NetScape at Linux Mandrake 8.0 that works fine. I have heard that it is possible with FireFox as well.

Best regards
Fredrik

The servlets that checks for changes:

package my.servlets;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

import my.servlets.*;
import my.tools.*;

import com.oreilly.servlet.*;
import com.oreilly.servlet.multipart.*;

public class ServerReload extends GeneralServlet
{
    public void start(HttpServletRequest request, HttpServletResponse response) throws IOException
    {
        ServletOutputStream out = response.getOutputStream();
        MultipartResponse multi = new MultipartResponse(response);

        int counter = 0;
        while(counter < 100)
        {
            String output = FileManager.getStringFor("counter.txt");
            int tempCounter = Integer.parseInt(output);

            if(counter != tempCounter)
            {
                multi.startResponse("text/plain");
                counter = tempCounter;
                out.println(counter);
                multi.endResponse();
            }

            try
            {
                Thread.sleep(1000);
            }
            catch (InterruptedException e)
            {
            }
        }
        multi.finish();
        out.close();
    }
}


The servlet that updates the counter.txt file:

package my.servlets.assignments1;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

import my.servlets.*;
import my.tools.*;

public class SecureFileAccess extends GeneralServlet
{
    public void start(HttpServletRequest request, HttpServletResponse response) throws IOException
    {
        response.setContentType("text/plain");
        out = new PrintWriter(response.getOutputStream());

        String output = null;
        synchronized(this)
        {
            try
            {
                output = FileManager.getStringFor("counter.txt");
                int counter = Integer.parseInt(output);
                output = ""+(++counter);
                FileManager.writeString("counter.txt", output, false);
            }
            catch(Exception e)
            {
                output = "1";
                FileManager.writeString("counter.txt", output, false);
            }
        }

        printString(output);
        flush();
    }
}