service.java

java Email you can use it to send email to others

		password = pw.getPassword();

		// have the service connect again
		connected = protocolConnect(host, port, user, password);
	    }
	}

	// if we're not connected by now, we give up
	if (!connected) {
	    if (authEx != null)
		throw authEx;
	    else
		throw new AuthenticationFailedException();
	}

	setURLName(new URLName(protocol, host, port, file, user, password));

	if (save)
	    session.setPasswordAuthentication(getURLName(),
			    new PasswordAuthentication(user, password));

	// set our connected state
	setConnected(true);

	// finally, deliver the connection event
	notifyConnectionListeners(ConnectionEvent.OPENED);
    }


    /**
     * The service implementation should override this method to
     * perform the actual protocol-specific connection attempt.
     * The default implementation of the <code>connect</code> method
     * calls this method as needed. <p>
     *
     * The <code>protocolConnect</code> method should return
     * <code>false</code> if a user name or password is required
     * for authentication but the corresponding parameter is null;
     * the <code>connect</code> method will prompt the user when
     * needed to supply missing information.  This method may
     * also return <code>false</code> if authentication fails for
     * the supplied user name or password.  Alternatively, this method
     * may throw an AuthenticationFailedException when authentication
     * fails.  This exception may include a String message with more
     * detail about the failure. <p>
     *
     * The <code>protocolConnect</code> method should throw an
     * exception to report failures not related to authentication,
     * such as an invalid host name or port number, loss of a
     * connection during the authentication process, unavailability
     * of the server, etc.
     *
     * @param	host		the name of the host to connect to
     * @param	port		the port to use (-1 means use default port)
     * @param	user		the name of the user to login as
     * @param	password	the user's password
     * @return	true if connection successful, false if authentication failed
     * @exception AuthenticationFailedException	for authentication failures
     * @exception MessagingException	for non-authentication failures
     */
    protected boolean protocolConnect(String host, int port, String user,
				String password) throws MessagingException {
	return false;
    }

    /**
     * Is this service currently connected? <p>
     *
     * This implementation uses a private boolean field to 
     * store the connection state. This method returns the value
     * of that field. <p>
     *
     * Subclasses may want to override this method to verify that any
     * connection to the message store is still alive.
     *
     * @return	true if the service is connected, false if it is not connected
     */
    public synchronized boolean isConnected() {
	return connected;
    }

    /**
     * Set the connection state of this service.  The connection state
     * will automatically be set by the service implementation during the
     * <code>connect</code> and <code>close</code> methods.
     * Subclasses will need to call this method to set the state
     * if the service was automatically disconnected. <p>
     *
     * The implementation in this class merely sets the private field
     * returned by the <code>isConnected</code> method.
     *
     * @param connected true if the service is connected,
     *                  false if it is not connected
     */
    protected synchronized void setConnected(boolean connected) {
	this.connected = connected;
    }

    /**
     * Close this service and terminate its connection. A close
     * ConnectionEvent is delivered to any ConnectionListeners. Any
     * Messaging components (Folders, Messages, etc.) belonging to this
     * service are invalid after this service is closed. Note that the service
     * is closed even if this method terminates abnormally by throwing
     * a MessagingException. <p>
     *
     * This implementation uses <code>setConnected(false)</code> to set
     * this service's connected state to <code>false</code>. It will then
     * send a close ConnectionEvent to any registered ConnectionListeners.
     * Subclasses overriding this method to do implementation specific
     * cleanup should call this method as a last step to insure event
     * notification, probably by including a call to <code>super.close()</code>
     * in a <code>finally</code> clause.
     *
     * @see javax.mail.event.ConnectionEvent
     * @throws	MessagingException	for errors while closing
     */
    public synchronized void close() throws MessagingException {
	setConnected(false);
	notifyConnectionListeners(ConnectionEvent.CLOSED);
    }

    /**
     * Return a URLName representing this service.  The returned URLName
     * does <em>not</em> include the password field.  <p>
     *
     * Subclasses should only override this method if their
     * URLName does not follow the standard format. <p>
     *
     * The implementation in the Service class returns (usually a copy of)
     * the <code>url</code> field with the password and file information
     * stripped out.
     *
     * @return	the URLName representing this service
     * @see	URLName
     */
    public synchronized URLName getURLName() {
	if (url != null && (url.getPassword() != null || url.getFile() != null))
	    return new URLName(url.getProtocol(), url.getHost(),
			url.getPort(), null /* no file */,
			url.getUsername(), null /* no password */);
	else
	    return url;
    }

    /**
     * Set the URLName representing this service.
     * Normally used to update the <code>url</code> field
     * after a service has successfully connected. <p>
     *
     * Subclasses should only override this method if their
     * URL does not follow the standard format.  In particular,
     * subclasses should override this method if their URL
     * does not require all the possible fields supported by
     * <code>URLName</code>; a new <code>URLName</code> should
     * be constructed with any unneeded fields removed. <p>
     *
     * The implementation in the Service class simply sets the
     * <code>url</code> field.
     *
     * @see URLName
     */
    protected synchronized void setURLName(URLName url) {
	this.url = url;
    }

    /**
     * Add a listener for Connection events on this service. <p>
     *
     * The default implementation provided here adds this listener
     * to an internal list of ConnectionListeners.
     *
     * @param l         the Listener for Connection events
     * @see             javax.mail.event.ConnectionEvent
     */
    public synchronized void addConnectionListener(ConnectionListener l) {
   	if (connectionListeners == null)
	    connectionListeners = new Vector();
	connectionListeners.addElement(l);
    }

    /**
     * Remove a Connection event listener. <p>
     *
     * The default implementation provided here removes this listener
     * from the internal list of ConnectionListeners.
     *
     * @param l         the listener
     * @see             #addConnectionListener
     */
    public synchronized void removeConnectionListener(ConnectionListener l) {
        if (connectionListeners != null)
	    connectionListeners.removeElement(l);
    }

    /**
     * Notify all ConnectionListeners. Service implementations are
     * expected to use this method to broadcast connection events. <p>
     *
     * The provided default implementation queues the event into
     * an internal event queue. An event dispatcher thread dequeues
     * events from the queue and dispatches them to the registered
     * ConnectionListeners. Note that the event dispatching occurs
     * in a separate thread, thus avoiding potential deadlock problems.
     */
    protected synchronized void notifyConnectionListeners(int type) {
   	if (connectionListeners != null) {
	    ConnectionEvent e = new ConnectionEvent(this, type);
	    queueEvent(e, connectionListeners);
	}

        /* Fix for broken JDK1.1.x Garbage collector :
         *  The 'conservative' GC in JDK1.1.x occasionally fails to
         *  garbage-collect Threads which are in the wait state.
         *  This would result in thread (and consequently memory) leaks.
         *
         * We attempt to fix this by sending a 'terminator' event
         * to the queue, after we've sent the CLOSED event. The
         * terminator event causes the event-dispatching thread to
         * self destruct.
         */
        if (type == ConnectionEvent.CLOSED)
            terminateQueue();
    }

    /**
     * Return <code>getURLName.toString()</code> if this service has a URLName,
     * otherwise it will return the default <code>toString</code>.
     */
    public String toString() {
	URLName url = getURLName();
	if (url != null)
	    return url.toString();
	else
	    return super.toString();
    }

    /*
     * The queue of events to be delivered.
     */
    private EventQueue q;

    /*
     * A lock for creating the EventQueue object.  Only one thread should
     * create an EventQueue for this service.  We can't synchronize on the
     * service's lock because that might violate the locking hierarchy in
     * some cases.
     */
    private Object qLock = new Object();

    /**
     * Add the event and vector of listeners to the queue to be delivered.
     */
    protected void queueEvent(MailEvent event, Vector vector) {
	// synchronize creation of the event queue
	synchronized (qLock) {
	    if (q == null)
		q = new EventQueue();
	}

	/*
         * Copy the vector in order to freeze the state of the set
         * of EventListeners the event should be delivered to prior
         * to delivery.  This ensures that any changes made to the
         * Vector from a target listener's method during the delivery
         * of this event will not take effect until after the event is
         * delivered.
         */
	Vector v = (Vector)vector.clone();
	q.enqueue(event, v);
    }

    static class TerminatorEvent extends MailEvent {
	private static final long serialVersionUID = 5542172141759168416L;

	TerminatorEvent() {
	    super(new Object());
	}

	public void dispatch(Object listener) {
	    // Kill the event dispatching thread.
	    Thread.currentThread().interrupt();
	}
    }

    // Dispatch the terminator
    private void terminateQueue() {
	synchronized (qLock) {
	    if (q != null) {
		Vector dummyListeners = new Vector();
		dummyListeners.setSize(1); // need atleast one listener
		q.enqueue(new TerminatorEvent(), dummyListeners);
		q = null;
	    }
	}
    }

    /**
     * Stop the event dispatcher thread so the queue can be garbage collected.
     */
    protected void finalize() throws Throwable {
	super.finalize();
	terminateQueue();
    }
}