多 Broker（或叢集）支援

版本 2.3 增加了在單個應用程式與多個代理或代理叢集之間通訊的便利性。在消費者端，主要的好處是基礎設施可以自動將自動宣告的佇列與適當的代理關聯起來。

透過一個示例可以最好地說明這一點

@SpringBootApplication(exclude = RabbitAutoConfiguration.class)
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    CachingConnectionFactory cf1() {
        return new CachingConnectionFactory("localhost");
    }

    @Bean
    CachingConnectionFactory cf2() {
        return new CachingConnectionFactory("otherHost");
    }

    @Bean
    CachingConnectionFactory cf3() {
        return new CachingConnectionFactory("thirdHost");
    }

    @Bean
    SimpleRoutingConnectionFactory rcf(CachingConnectionFactory cf1,
            CachingConnectionFactory cf2, CachingConnectionFactory cf3) {

        SimpleRoutingConnectionFactory rcf = new SimpleRoutingConnectionFactory();
        rcf.setDefaultTargetConnectionFactory(cf1);
        rcf.setTargetConnectionFactories(Map.of("one", cf1, "two", cf2, "three", cf3));
        return rcf;
    }

    @Bean("factory1-admin")
    RabbitAdmin admin1(CachingConnectionFactory cf1) {
        return new RabbitAdmin(cf1);
    }

    @Bean("factory2-admin")
    RabbitAdmin admin2(CachingConnectionFactory cf2) {
        return new RabbitAdmin(cf2);
    }

    @Bean("factory3-admin")
    RabbitAdmin admin3(CachingConnectionFactory cf3) {
        return new RabbitAdmin(cf3);
    }

    @Bean
    public RabbitListenerEndpointRegistry rabbitListenerEndpointRegistry() {
        return new RabbitListenerEndpointRegistry();
    }

    @Bean
    public RabbitListenerAnnotationBeanPostProcessor postProcessor(RabbitListenerEndpointRegistry registry) {
        MultiRabbitListenerAnnotationBeanPostProcessor postProcessor
                = new MultiRabbitListenerAnnotationBeanPostProcessor();
        postProcessor.setEndpointRegistry(registry);
        postProcessor.setContainerFactoryBeanName("defaultContainerFactory");
        return postProcessor;
    }

    @Bean
    public SimpleRabbitListenerContainerFactory factory1(CachingConnectionFactory cf1) {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(cf1);
        return factory;
    }

    @Bean
    public SimpleRabbitListenerContainerFactory factory2(CachingConnectionFactory cf2) {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(cf2);
        return factory;
    }

    @Bean
    public SimpleRabbitListenerContainerFactory factory3(CachingConnectionFactory cf3) {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(cf3);
        return factory;
    }

    @Bean
    RabbitTemplate template(SimpleRoutingConnectionFactory rcf) {
        return new RabbitTemplate(rcf);
    }

    @Bean
    ConnectionFactoryContextWrapper wrapper(SimpleRoutingConnectionFactory rcf) {
        return new ConnectionFactoryContextWrapper(rcf);
    }

}

@Component
class Listeners {

    @RabbitListener(queuesToDeclare = @Queue("q1"), containerFactory = "factory1")
    public void listen1(String in) {

    }

    @RabbitListener(queuesToDeclare = @Queue("q2"), containerFactory = "factory2")
    public void listen2(String in) {

    }

    @RabbitListener(queuesToDeclare = @Queue("q3"), containerFactory = "factory3")
    public void listen3(String in) {

    }

}

如你所見，我們聲明瞭 3 組基礎設施（連線工廠、管理員、容器工廠）。如前所述，@RabbitListener 可以定義要使用的容器工廠；在這種情況下，它們還使用 queuesToDeclare，這會導致佇列（如果不存在）在代理上被宣告。透過以 <container-factory-name>-admin 的約定命名 RabbitAdmin bean，基礎設施能夠確定哪個管理員應該宣告佇列。這也適用於 bindings = @QueueBinding(…)，其中交換機和繫結也將被宣告。它不適用於 queues，因為後者期望佇列已經存在。

在生產者端，提供了方便的 ConnectionFactoryContextWrapper 類，以簡化 RoutingConnectionFactory（參見路由連線工廠）的使用。

如上所示，已添加了一個 SimpleRoutingConnectionFactory bean，路由鍵為 one、two 和 three。還有一個使用該工廠的 RabbitTemplate。以下是使用該模板和包裝器路由到其中一個代理叢集的示例。

@Bean
public ApplicationRunner runner(RabbitTemplate template, ConnectionFactoryContextWrapper wrapper) {
    return args -> {
        wrapper.run("one", () -> template.convertAndSend("q1", "toCluster1"));
        wrapper.run("two", () -> template.convertAndSend("q2", "toCluster2"));
        wrapper.run("three", () -> template.convertAndSend("q3", "toCluster3"));
    };
}