Reading data from a thread ( in a Servlet)

Question

I'm using the ServletContextListener to create a new thread.

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.util.concurrent.*;

    public class Port implements ServletContextListener {
        private ExecutorService executor;

        public void contextDestroyed(ServletContextEvent event) {
            executor.shutdown();

        }

        public void contextInitialized(ServletContextEvent event) { 
            // start task
            executor = Executors.newSingleThreadExecutor();
            executor.submit(new Task()); //task should implement Runnable!

        }
    }

Inside this thread I'm reading data from a serial port (SerialPortEventListener). The task.class should read out information from the serial port during the whole period in which the server is active. I've thrown this inside a thread because there can only be one instance that reads from the serial port; data should then be shared to all clients.

Now I would like to acces the data this thread is reading from the serial port.

Can this be done? And if yes then how?

Answer 1

You could, for example, store the read data in a servlet context attribute. Then, from the other classes, you would get the attribute from the servlet context:

public void contextInitialized(final ServletContextEvent event) { 
        // start task
        executor = Executors.newSingleThreadExecutor();
        executor.submit(new Runnable() {
            @Override
            public void run() {
                String data = readFromPort();
                event.getServletContext().setAttribute("serialPortData", data); 
            }
        });
    }
}