Topics vs Queues

Topics:

• A JMS Topic implements publish and subscribe semantics.
• When you publish a message it goes to all the subscribers who are interested - so zero to many subscribers will receive a copy of the message.
• Only subscribers who had an active subscription at the time the broker receives the message will get a copy of the message.

    Topics = Insert > Broadcast (send to all subscribers) 1:n

Queues:

• A JMS Queue implements load balancer semantics. 
• A single message will be received by exactly one consumer. 
• If there are no consumers available at the time the message is sent it will be kept until a consumer is available that can process the message. If a consumer receives a message and does not acknowledge it before closing then the message will be redelivered to another consumer. 
• A queue can have many consumers with messages load balanced across the available consumers.

    Queues = Insert > Withdraw (send to single subscriber) 1:1

Queues vs Topics