ActiveMQ Connection is not working - jms

Question

I created the ActiveMQ Connection with ActiveMQConnectionFactory,
connectionFactory = new ActiveMQConnectionFactory("nio://0.0.0.0:" + activeMqPort);
connection = connectionFactory.createConnection();
connection.start();
Later some point of time I am using the connection to get the session:
Session session = connection.createSession(false, Session.CLIENT_ACKNOWLEDGE);
While creating session from Connection it will fail with a NullPointerException (connection is null),
PS: Connection was working before, suddenly its null.
Can anyone explain it to me when this will happen and how to fix this ?

Answer 1

Your URI is incorrect for a client-side connection. nio:// is only relevant on the server-side, and specifying "0.0.0.0" is used by the server-side to instruct the server to listen on all ip interfaces.
Try this instead to connect to an ActiveMQ server running on the same computer as this client code:
connectionFactory = new ActiveMQConnectionFactory("tcp://localhost:" + activeMqPort);
connection = connectionFactory.createConnection();
connection.start();
Session session = connection.createSession(false, Session.CLIENT_ACKNOWLEDGE);
Bonus recommendations:
Externalize the entire client url, not just the port. This will allow you to specify multiple servers for failover, reconnect timeout parameters and other client connectivity settings that would otherwise require a code change.
Do not use CLIENT_ACKNOWLEDGE unless you really know what it does. Its is a source of a lot of pain and suffering if you don't clearly have a handle on how it works. If you want per-message Acknowledgement, use ActiveMQSession.INDIVIDUAL_ACKNOWLEDGE. For non-transacted, use Session.AUTO_ACKNOWLEDGE.