temperaturesensorserver.java

Java网络编程与分布式计算, 主要分析java网络各方面的编程, 提供许多实用安全

import java.util.*;
import java.rmi.*;
import java.rmi.server.*;

// Chapter 11, Listing 7
public class TemperatureSensorServer extends UnicastRemoteObject implements TemperatureSensor, Runnable
{
	private volatile double  temp;
	private Vector list = new Vector();

	public TemperatureSensorServer() throws java.rmi.RemoteException
	{
		// Assign a default setting for the temperature
		temp = 98.0;
	}

	public double getTemperature() throws java.rmi.RemoteException
	{
		return temp;
	}

	public void  addTemperatureListener ( TemperatureListener listener ) 
		throws java.rmi.RemoteException
	{
		System.out.println ("adding listener -" + listener);
		list.add (listener);
	}

	public void  removeTemperatureListener ( TemperatureListener listener )
		throws java.rmi.RemoteException
	{
		System.out.println ("removing listener -" + listener);
		list.remove (listener);
	}

	public void run()
	{
		Random r = new Random();

		for (;;)			
		{
			try
			{
				// Sleep for a random amount of time
				int duration = r.nextInt() % 10000 + 2000;

				// Check to see if negative, if so, reverse
				if (duration < 0) duration = duration * -1;

				Thread.sleep(duration);
			}
			catch (InterruptedException ie) { }

			// Get a number, to see if temp goes up or down
			int num = r.nextInt();

			if (num < 0)
			{
				temp += 0.5;				
			}
			else
			{
				temp -= 0.5;				
			}

			// Notify registered listeners
			notifyListeners();
		}
	}

	private void notifyListeners()
	{
		// Notify every listener in the registered list
		for (Enumeration e = list.elements(); e.hasMoreElements(); )
		{
			TemperatureListener listener = (TemperatureListener) e.nextElement();

			// Notify, if possible a listener
			try
			{
				listener.temperatureChanged (temp);
			}
			catch (RemoteException re)
			{
				System.out.println ("removing listener -" + listener);
				// Remote the listener
				list.remove( listener );
			}
		}
	}

	public static void main(String args[])
	{
		System.out.println ("Loading temperature service");

		// Only required for dynamic class loading
		//System.setSecurityManager ( new RMISecurityManager() );

		try
		{
			// Load the service
			TemperatureSensorServer sensor = new TemperatureSensorServer();
			
			// Check to see if a registry was specified
			String registry = "localhost";
			if (args.length >=1)
			{
				registry = args[0];
			}

			// Registration format //registry_hostname (optional):port /service
			String registration = "rmi://" + registry + "/TemperatureSensor";
			
			// Register with service so that clients can find us
			Naming.rebind( registration, sensor );

			// Create a thread, and pass the sensor server.
			// This will activate the run() method, and trigger
			// regular temperature changes.
			Thread thread = new Thread (sensor);
			thread.start();

		}
		catch (RemoteException re)
		{
			System.err.println ("Remote Error - " + re);
		}
		catch (Exception e)
		{
			System.err.println ("Error - " + e);
		}
	}
}