Encapsulates mail transport agent with FIFO queue and non-blocking send capabilities. More...

Collaboration diagram for MailTransport:

Classes
interface	Context
	Provides message presentation and call-back context for the instance of `MailTransport` class. More...
Public Member Functions
	MailTransport (Context context, String smtpServer, int smtpPort)
	Creates instance of the mail transport with the (new) session to SMTP server.
int	getQueueSize ()
	Gets number of messages in the queue.
void	startSending ()
	Starts the worker thread (if not already started)
void	noMoreMessages ()
	Sends QUIT message to the worker thread.
void	enqueueMessage (String from, String[] to, String subject, String textMessage) throws MessagingException
	Creates and puts new MIME text message into outgoing queue.
void	run ()
	Waits for messages to become available in the queue, then takes messages (first-in first-out) from the queue and relays them through the session to remote SMTP server.
Private Attributes
Thread	workerThread = null
	Instance of the main thread.
Context	context = null
	Presentation contexts.
Session	session = null
	Session to SMTP server.
LinkedBlockingQueue< Message >	queue = null
	FIFO message queue served by worker thread.
Message	quitSignal = null
	The special message used to signal the worker thread to stop processing of messages and terminate.

Detailed Description

Encapsulates mail transport agent with FIFO queue and non-blocking send capabilities.

Instances of this class may be used in two different scenarios (note the position of MailTransport.startSending() method and the usage of MailTransport.noMoreMessages() bellow):

Scenario 1: Sends one ore more messages at once.

Usage:

create instance using constructor MailTransport.MailTransport() (with SMTP server as parameter)
call MailTransport.enqueueMessage()
[ call MailTransport.enqueueMessage() ]...
call MailTransport.noMoreMessages() to terminate worker thread
call MailTransport.startSending()

Scenario 2. Works in background as relay client to SMTP server.

Usage:

create instance using constructor MailTransport.MailTransport() (with SMTP server as parameters)
call MailTransport.startSending()
call MailTransport.enqueueMessage()
[ call MailTransport.enqueueMessage() ]...

Author:: Mikica B Kocic

Definition at line 44 of file MailTransport.java.

Constructor & Destructor Documentation

MailTransport.MailTransport	(	Context	context,
		String	smtpServer,
		int	smtpPort
	)

Creates instance of the mail transport with the (new) session to SMTP server.

Definition at line 97 of file MailTransport.java.

References context, queue, quitSignal, and session.

    {
        this.context    = context;
        this.queue      = new LinkedBlockingQueue<Message> ();
        this.quitSignal = new MimeMessage( this.session );

        Properties relayHost = new Properties();
        relayHost.put( "mail.smtp.host", smtpServer );
        relayHost.put( "mail.smtp.port", smtpPort );

        /* Create instance of the session.
         * DO NOT USE: getDefaultInstance() as it will create cached session.
         */
        this.session = Session.getInstance( relayHost, null ); 
    }

Member Function Documentation

void MailTransport.enqueueMessage	(	String	from,
		String[]	to,
		String	subject,
		String	textMessage
	)		throws MessagingException

Creates and puts new MIME text message into outgoing queue.

Definition at line 157 of file MailTransport.java.

References queue, and session.

Referenced by SendMailApp.enqueueMessage().

    {
        InternetAddress[] toAddr = new InternetAddress[ to.length ];
        for( int i = 0; i < to.length; i++ ) {
            toAddr[i] = new InternetAddress( to[i] );
        }

        MimeMessage mimeMsg = new MimeMessage( session );
        mimeMsg.setFrom( new InternetAddress( from ) );
        mimeMsg.setRecipients( Message.RecipientType.TO, toAddr );
        mimeMsg.setHeader( "X-Mailer", "IP1-MailSender" );
        mimeMsg.setSubject( subject );
        mimeMsg.setContent( textMessage, "text/plain" );

        /* Places the message into outgoing queue...
         */
        try {
            this.queue.put( mimeMsg );
        } catch( InterruptedException e ) {
            /* ignore */
        }
    }

int MailTransport.getQueueSize ( )

Gets number of messages in the queue.

Definition at line 116 of file MailTransport.java.

References queue.

Referenced by SendMailApp.enqueueMessage(), and SendMailApp.onSendCompleted().

    {
        return this.queue.size ();
    }

void MailTransport.noMoreMessages ( )

Sends QUIT message to the worker thread.

Definition at line 140 of file MailTransport.java.

References queue, and quitSignal.

Referenced by SendMailApp.enqueueMessage(), and SendMailApp.formWindowClosing().

    {
        synchronized( this )
        {
            /* put the 'QUIT' message into queue
             */
            try {
                this.queue.put( this.quitSignal );
            } catch( InterruptedException e ) {
                /* ignore */
            }
        }
    }

void MailTransport.run ( )

Waits for messages to become available in the queue, then takes messages (first-in first-out) from the queue and relays them through the session to remote SMTP server.

After receiving special 'QUIT' message, the worker thread terminates. In case of error, thread also quits and reports the error using Context.onSendCompleted() from the MailTransport.Context call-back interface.

Definition at line 191 of file MailTransport.java.

References context, MailTransport.Context.onSendCompleted(), MailTransport.Context.println(), queue, quitSignal, and workerThread.

    {
        context.println( "MailTransport(" + workerThread.getId () 
                + "): Worker thread started..." );
        
        context.println( "MailTransport(" + workerThread.getId () 
                + "): Found " + queue.size() + " messages in queue." );
        
        String errorMessage = null; // error to be reported to the owner
        int curMessageNo = 0; // keeps track of the current message id

        while( true )
        {
            Message msgToSend = null;

            /* Retrieves and removes the head message from the queue,
             * waiting if necessary until an element becomes available).
             * Terminates the thread in case of interrupt.
             */
            try {
                context.println( "MailTransport(" + workerThread.getId () 
                        + "): Waiting for messsages..." );
                msgToSend = this.queue.take ();
            } catch( InterruptedException e ) {
                break;
            }

            /* Terminates the thread if the last retrieved message is
             * the 'QUIT thread' message.
             */
            if ( msgToSend == quitSignal || msgToSend == null ) {
                context.println( "MailTransport(" + workerThread.getId () 
                        + "): Got signal to 'QUIT'..." );
                break;
            }

            /* Sends message via transport protocol
             */
            try
            {
                ++curMessageNo;
                
                context.println( "MailTransport(" + workerThread.getId () 
                        + "): Sending message #" + curMessageNo + "..." );
                
                for( javax.mail.Address a : msgToSend.getFrom() ) {
                    context.println( "    From:    " + a.toString () );
                }
                for( javax.mail.Address a : msgToSend.getRecipients( RecipientType.TO ) ) {
                    context.println( "    To:      " + a.toString () );
                }
                context.println( "    Subject: " + msgToSend.getSubject () );

                Transport.send( msgToSend );
                
                context.println( "MailTransport(" + workerThread.getId () 
                        + "): MESSAGE SENT!" );
            }
            catch( MessagingException e )
            {
                context.println( "MailTransport(" + workerThread.getId () 
                        + "): Error\n\n" + e.toString () + "\n" );
                
                errorMessage = e.toString ();

                break; // there is no point to continue in case of error...
            }
        }
        
        context.println( "MailTransport(" + workerThread.getId () 
                + "): Thread done." );
        
        context.onSendCompleted( errorMessage );
    }

void MailTransport.startSending ( )

Starts the worker thread (if not already started)

Definition at line 124 of file MailTransport.java.

References workerThread.

Referenced by SendMailApp.enqueueMessage().

    {
        synchronized( this )
        {
            if ( workerThread != null ) {
                return; // already started (there can be only one worker thread)
            }

            this.workerThread = new Thread( this );
            this.workerThread.start ();
        }
    }