How to bind to topic with Spring AMQP only if exchange exists? - spring

Question

I need to bind a queue to a topic exchange, but:
Only if the topic exists
If the topic exists, use the existing settings (e.g. durable, auto-delete, etc)
Reason is, I need a 3rd party application to create the exchange with whatever settings they want to use, I don't want to modify the topic settings.
I put the code below together by reading RabbitMQ Spring AMQP tutorial. It works, but creates an exchange if doesn't exist.
#Configuration
public class BeanConfiguration {
#Bean
public TopicExchange topic() {
return new TopicExchange("MyTopicExchange", true, false);
}
#Bean
public Queue queue() {
return QueueBuilder.durable("MyQueue").build();
}
#Bean
public Binding binding(TopicExchange topicExchange, Queue queue) {
return BindingBuilder.bind(queue).to(topicExchange).with("purchases.*");
}
}

Answer 1

I found a way by using superclass method setShouldDeclareFalse:
#Bean
public TopicExchange topic() {
TopicExchange topicExchange = new TopicExchange("MyTopicExchange", true, false);
topicExchange.setShouldDeclare(false);
return topicExchange;
}

Answer 2

Skip the exchange declaration bean and ignore the binding declaration failure.
#SpringBootApplication
public class So59994152Application {
public static void main(String[] args) {
SpringApplication.run(So59994152Application.class, args);
}
#Bean
public Queue queue() {
return QueueBuilder.durable("MyQueue").build();
}
#Bean
public Binding binding(Queue queue, AmqpAdmin admin) {
((RabbitAdmin) admin).setIgnoreDeclarationExceptions(true);
return new Binding("MyQueue", DestinationType.QUEUE, "MyTopicExchange", "purchases.*", null);
}
#Bean
public ApplicationRunner runner(CachingConnectionFactory cf) {
return args -> {
cf.createConnection();
cf.destroy();
};
}
}
If you are not using Spring Boot; set the admin property in the admin bean.