Trying to implement a mail queue

Question

I'm trying to implement a very basic mail queue using ExecutorService and a Callable split into a producer which builds the email and an email queue and a consumer to send the queued message out but I keep getting:
java.lang.NullPointerException
     at javax.mail.Transport.send(Transport.java:97)
     at org.bedework.mail.sendMail.call(sendMail.java:45)
     at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
     at java.util.concurrent.FutureTask.run(Unknown Source)
     at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
     at java.lang.Thread.run(Unknown Source)
I'm not sure how to get the transport variable passed across and read by the consumer thread.
The consumer code is:
public class sendMail implements Callable<Object> {
     private ArrayBlockingQueue<Object>  queuedMail;
     private Transport trans;
     private MimeMessage msg;
     private Logger log = Logger.getLogger(sendMail.class);
     public sendMail (ArrayBlockingQueue<Object> queuedMail, Transport trans) {
          this.trans = trans;
          this.queuedMail = queuedMail;
     public Object call() throws Exception {
          try {
               queuedMail.poll();
               synchronized (queuedMail) {
                  if (queuedMail.isEmpty()) {
                     queuedMail.wait(1000);
               try {
                    trans.send(msg);
                    Thread.sleep(1000);
               } catch (Exception e) {
                    e.printStackTrace();
          } catch (Exception e) {
               e.printStackTrace();
          return null;
}The code that calls it is:
tr = sess.getTransport(config.getProtocol());
        pool.submit(new buildMail(sess, cal, originator, to, subject));
        pool.submit(new sendMail (mailqueue, tr));I'd be grateful for any pointers in getting this sorted out.

Answer 1

First, read this FAQ item:
[http://java.sun.com/products/javamail/FAQ.html#send|http://java.sun.com/products/javamail/FAQ.html#send]
Then explain to me how "msg" is ever set in your sendMail class.