在ThreadLocal中包装JMS连接时拒绝连接

Question

Running into an issue where connection.start() fails due to

java.net.ConnectException: Connection refused: connect

when I wrap my javax.jms.TopicConnection in a ThreadLocal , as follows:

private ThreadLocal<TopicConnection> createThreadLocalTopicConnection(final TopicConnectionFactory cf)
{
    return new ThreadLocal<TopicConnection>() {
        public TopicConnection result;

        protected synchronized TopicConnection initialValue() {
            try {
                // Returns a javax.jms.TopicConnection object.
                result = cf.createTopicConnection();
                result.start();
                return result;
            } catch (JMSException e) {
                throw new RuntimeException(e);
            }
        }

            protected void finalize() throws Throwable {
                if(result!=null) result.close();
            }
        };
    }

If I just create the TopicConnection as a bare static variable, it connects without any issues. Can anybody explain why it would work as a bare variable but when wrapped in a ThreadLocal it would fail? Google has failed me pretty spectacularly this time around.

Answer 1

It's hard to say exactly why this is happening, but JMS clients are usually multi-threaded beasts, so I can see that this strategy might not be totally kosher.

JMS Connections are intended to be thread-safe, you you might want to just wrap your connection in a singleton or something. (JMS Sessions and below are not thread-safe and should not be shared by threads, so you might consider putting the session in a thread local if you're committed to this approach).

Answer 2

ThreadLocal would mean every Thread is getting it's own Connection. Do compare how many threads the application is spawning vs the number of connections in the ActivationSpec