Saturday, January 15, 2011

Teach Spring to use per-listener JMS destination queue names, not hard-coded ones

This took some experimenting.

My problem: I am using Spring Framework 3.0 JMS support to wire up a JMS listener container to listener beans. The XML syntax looks like:

<jms:listener-container>
    <jms:listener
            destination="hard-coded-queue-name"
            ref="listener"/>
</jms:listener-container>

This XML is distributed with each program instance. Not a single single server or client instance but a server cluster or client farm: each one of these needs a unique destination so JMS routes correctly.

My first try fixed the uniqueness problem but was less than fully usable:

<jms:listener-container>
    <jms:listener
            destination="#{T(java.util.UUID).randomUUID().toString()}"
            ref="listener"/>
</jms:listener-container>

This suffers excess cleverness. Each listener gets a random UUID for its destination. But, how does the listener refer to this queue name when filling in a JMS reply-to field, or logging or other purposes?

The real answer is to ask the listener for a destination, no produce one externally:

<jms:listener-container>
    <jms:listener
            destination="#{listener.inbox}"
            ref="listener"/>
</jms:listener-container>

And in the listener:

private final String inbox = UUID.randomUUID().toString();

public String getInbox() {
    return inbox;
}
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