Red Hat Summit Red Hat SummitSupportConsoleDéveloppeursCommencer un essaiContact

Ce contenu n'est pas disponible dans la langue sélectionnée.

4.6.3. Subscribe to the Default Exchange

To subscribe to the Default Exchange, create a receiver and pass the name of the queue to the constructor. For example, to subscribe to the queue "quick-publish", using the Python API:
C++
Receiver receiver = session.createReceiver('quick-publish');
Copy to Clipboard Toggle word wrap
Python
receiver = session.receiver('quick-publish')
Copy to Clipboard Toggle word wrap
This receiver can now be used to retrieve messages from the quick-publish queue.
To obtain a browse-only view that does not remove messages from the queue:
C++
Receiver receiver = session.createReceiver('quick-publish; {mode: browse}');
Copy to Clipboard Toggle word wrap
Python
receiver = session.receiver('quick-publish; {mode: browse}')
Copy to Clipboard Toggle word wrap
If you want to create and subscribe a queue that does not yet exist, for example for your application to request its own copies of messages, use the create parameter:
C++
Receiver receiver = session.createReceiver("my-own-copies-please; {create: always, node: {type: 'queue'}}");
Copy to Clipboard Toggle word wrap
Python
receiver = session.receiver("my-own-copies-please; {create: always, node: {type: 'queue'}}")
Copy to Clipboard Toggle word wrap
If the queue "my-own-copies-please" already exists, then your receiver will connect to that queue. If the queue does not exist, then it will be created (all of this assumes sufficient privileges, of course).
One thing to bear in mind is that if an exchange named "my-own-copies-please" exists, your receiver will silently connect to that in preference to creating a queue. This is not what you intended, and will have unpredictable results. To avoid this, you can use the assert parameter, like this:
C++
try {
  Receiver receiver = session.createReceiver("my-own-copies-please; {create: always, assert: always, node: {type: 'queue'}}");
} catch(const std::exception& error) {
  std::cerr << error.what() << std::endl;
}
Copy to Clipboard Toggle word wrap
Python
try:
  receiver = session.receiver("my-own-copies-please; {create: always, assert: always, node: {type: 'queue'}}")
except MessagingError m:
  print m
Copy to Clipboard Toggle word wrap
Now if "my-own-copies-please" already exists and is an exchange, the receiver constructor will raise an exception: "expected queue, got topic".
Note that although it is an instance of a Direct Exchange, the Default Exchange does not allow multiple bindings using the same key. Each queue is bound to the Default Exchange uniquely. This means that you can only connect to a queue to get messages sent to it; you cannot bind another queue to the exchange in parallel to receive copies of the messages, as you can with other Direct Exchanges.

See Also:

Report a bug
Retour au début
Red Hat logoGithubredditYoutubeTwitter

Apprendre

Essayez, achetez et vendez

Communautés

À propos de la documentation Red Hat

Nous aidons les utilisateurs de Red Hat à innover et à atteindre leurs objectifs grâce à nos produits et services avec un contenu auquel ils peuvent faire confiance. Découvrez nos récentes mises à jour.

Rendre l’open source plus inclusif

Red Hat s'engage à remplacer le langage problématique dans notre code, notre documentation et nos propriétés Web. Pour plus de détails, consultez le Blog Red Hat.

À propos de Red Hat

Nous proposons des solutions renforcées qui facilitent le travail des entreprises sur plusieurs plates-formes et environnements, du centre de données central à la périphérie du réseau.

Theme

© 2025 Red Hat