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MatConsoleCtl - control MATLAB from Java
There is a newer version: 4.6.0
/*
 * Code licensed under new-style BSD (see LICENSE).
 * All code up to tags/original: Copyright (c) 2013, Joshua Kaplan
 * All code after tags/original: Copyright (c) 2016, DiffPlug
 */
package matlabcontrol;

import java.rmi.NoSuchObjectException;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
import java.util.Timer;
import java.util.TimerTask;

/**
 * Enables a session of MATLAB to be connected to by matlabcontrol running outside MATLAB.
 * 
 * @since 4.0.0
 * 
 * @author Joshua Kaplan
 */
class MatlabBroadcaster {
	/**
	 * A reference to the RMI registry which holds {@code MatlabSession}s.
	 */
	private static Registry _registry = null;

	/**
	 * Represents this session of MATLAB.
	 */
	private static final MatlabSessionImpl _session = new MatlabSessionImpl();

	/**
	 * The frequency (in milliseconds) with which to check if the connection to the registry still exists.
	 */
	private static final int BROADCAST_CHECK_PERIOD = 1000;

	/**
	 * The timer used to check if still connected to the registry.
	 */
	private static final Timer _broadcastTimer = new Timer("MLC Broadcast Maintainer");

	/**
	 * Private constructor so this class cannot be constructed.
	 */
	private MatlabBroadcaster() {}

	/**
	 * Returns the session object bound to the RMI registry by this broadcaster.
	 * 
	 * @return 
	 */
	static MatlabSessionImpl getSession() {
		return _session;
	}

	/**
	 * Makes this session of MATLAB visible to matlabcontrol. Once broadcasting, matlabcontrol running outside MATLAB
	 * will be able to connect to this session of MATLAB.
	 * 
	 * @throws MatlabConnectionException thrown if not running inside MATLAB or unable to broadcast
	 */
	synchronized static void broadcast(int broadcastPort) throws MatlabConnectionException {
		//If the registry hasn't been created
		if (_registry == null) {
			//Create or retrieve an RMI registry
			setupRegistry(broadcastPort);

			//Register this session so that it can be reconnected to
			bindSession();

			//If the registry becomes disconnected, either create a new one or locate a new one
			maintainRegistryConnection(broadcastPort);
		}
	}

	/**
	 * Attempts to create a registry, and if that cannot be done, then attempts to get an existing registry.
	 * 
	 * @throws MatlabConnectionException if a registry can neither be created nor retrieved
	 */
	private static void setupRegistry(int broadcastPort) throws MatlabConnectionException {
		try {
			_registry = LocalHostRMIHelper.createRegistry(broadcastPort);
		}
		//If we can't create one, try to retrieve an existing one
		catch (Exception e) {
			try {
				_registry = LocalHostRMIHelper.getRegistry(broadcastPort);
			} catch (Exception ex) {
				throw new MatlabConnectionException("Could not create or connect to the RMI registry", ex);
			}
		}
	}

	/**
	 * Binds the session object, an instance of {@link MatlabSession} to the registry with {@link #SESSION_ID}.
	 * 
	 * @throws MatlabConnectionException 
	 */
	private static void bindSession() throws MatlabConnectionException {
		//Unexport the object, it will throw an exception if it is not bound - so ignore that
		try {
			UnicastRemoteObject.unexportObject(_session, true);
		} catch (NoSuchObjectException e) {}

		try {
			_registry.bind(_session.getSessionID(), LocalHostRMIHelper.exportObject(_session));
		} catch (Exception e) {
			throw new MatlabConnectionException("Could not register this session of MATLAB", e);
		}
	}

	/**
	 * Checks with a timer that the registry still exists and that the session object is exported to it. If either
	 * stop being the case then an attempt is made to re-establish.
	 */
	private static void maintainRegistryConnection(final int broadcastPort) {
		//Configure the a timer to monitor the broadcast
		_broadcastTimer.schedule(new TimerTask() {
			@Override
			public void run() {
				//Check if the registry is connected
				try {
					//Will succeed if connected and the session object is still exported
					_registry.lookup(_session.getSessionID());
				}
				//Session object is no longer exported
				catch (NotBoundException e) {
					try {
						bindSession();
					}
					//Nothing more can be done if this fails
					catch (MatlabConnectionException ex) {}
				}
				//Registry is no longer connected
				catch (RemoteException e) {
					try {
						setupRegistry(broadcastPort);
						bindSession();
					}
					//Nothing more can be done if this fails
					catch (MatlabConnectionException ex) {}
				}
			}
		}, BROADCAST_CHECK_PERIOD, BROADCAST_CHECK_PERIOD);
	}
}