2.9 RabbitMQ整合Spring AMQP實戰（二）- SpringAMQP 聲明

在Rabbit基礎API裏面聲明一個Exchange、聲明一個綁定、一個隊列的方式如下：

使用Spring AMQP聲明，就需要用Spring AMQP 的如下模式，即聲明式@Bean方式。

在RabbitMQConfig中定義如下代碼：

 /*------------------- 聲明TopicExchange：topic001 隊列：queue001 交換機和隊列綁定 -------------------------*/
    @Bean
    public TopicExchange exchange001() {
        return new TopicExchange("topic001", true, false);
    }
    @Bean
    public Queue queue001() {
        //隊列持久
        return new Queue("queue001", true);
    }
    @Bean
    public Binding binding001() {
        return BindingBuilder.bind(queue001()).to(exchange001()).with("spring.*");
    }

    /*------------------- 聲明TopicExchange：topic002 隊列：queue002 交換機和隊列綁定 -------------------------*/
    @Bean
    public TopicExchange exchange002() {
        return new TopicExchange("topic002", true, false);
    }
    @Bean
    public Queue queue002() {
        //隊列持久
        return new Queue("queue002", true);
    }
    @Bean
    public Binding binding002() {
        return BindingBuilder.bind(queue002()).to(exchange002()).with("rabbit.*");
    }

    /*------------------- 聲明隊列：queue003 交換機exchange001和隊列綁定 -------------------------*/
    @Bean
    public Queue queue003() {
        //隊列持久
        return new Queue("queue003", true);
    }
    @Bean
    public Binding binding003() {
        return BindingBuilder.bind(queue003()).to(exchange001()).with("mq.*");
    }

    /*--------------------定義一個image_queue隊列和一個pdf_queue------------*/
    @Bean
    public Queue queue_image() {
        //隊列持久
        return new Queue("image_queue", true);
    }
    @Bean
    public Queue queue_pdf() {
        //隊列持久
        return new Queue("pdf_queue", true);
    }

代碼解析：
定義了2個交換機、5個隊列，其中的交換機和隊列的綁定關係入代碼所示。
啓動之前寫的測試方法觀察是否創建成功

觀察管理頁面，相應隊列和綁定關係創建成功



SpringAMQP 聲明源碼分析
step1. 查看RabbitAdmin源碼

step 2 . InitializingBean
在InitializingBean中初始化之前做的方法afterPropertiesSet

step3. 查看RabbitAdmin中的afterPropertiesSet方法

step4. initialize函數

創建了三個隊列，用於存放交換機、隊列綁定關係

public void initialize() {

		if (this.applicationContext == null) {
			this.logger.debug("no ApplicationContext has been set, cannot auto-declare Exchanges, Queues, and Bindings");
			return;
		}

		this.logger.debug("Initializing declarations");
		Collection<Exchange> contextExchanges = new LinkedList<Exchange>(
				this.applicationContext.getBeansOfType(Exchange.class).values());
		Collection<Queue> contextQueues = new LinkedList<Queue>(
				this.applicationContext.getBeansOfType(Queue.class).values());
		Collection<Binding> contextBindings = new LinkedList<Binding>(
				this.applicationContext.getBeansOfType(Binding.class).values());

		processLegacyCollections(contextExchanges, contextQueues, contextBindings);
		processDeclarables(contextExchanges, contextQueues, contextBindings);

		final Collection<Exchange> exchanges = filterDeclarables(contextExchanges);
		final Collection<Queue> queues = filterDeclarables(contextQueues);
		final Collection<Binding> bindings = filterDeclarables(contextBindings);

		for (Exchange exchange : exchanges) {
			if ((!exchange.isDurable() || exchange.isAutoDelete())  && this.logger.isInfoEnabled()) {
				this.logger.info("Auto-declaring a non-durable or auto-delete Exchange ("
						+ exchange.getName()
						+ ") durable:" + exchange.isDurable() + ", auto-delete:" + exchange.isAutoDelete() + ". "
						+ "It will be deleted by the broker if it shuts down, and can be redeclared by closing and "
						+ "reopening the connection.");
			}
		}

		for (Queue queue : queues) {
			if ((!queue.isDurable() || queue.isAutoDelete() || queue.isExclusive()) && this.logger.isInfoEnabled()) {
				this.logger.info("Auto-declaring a non-durable, auto-delete, or exclusive Queue ("
						+ queue.getName()
						+ ") durable:" + queue.isDurable() + ", auto-delete:" + queue.isAutoDelete() + ", exclusive:"
						+ queue.isExclusive() + ". "
						+ "It will be redeclared if the broker stops and is restarted while the connection factory is "
						+ "alive, but all messages will be lost.");
			}
		}

		if (exchanges.size() == 0 && queues.size() == 0 && bindings.size() == 0) {
			this.logger.debug("Nothing to declare");
			return;
		}
		this.rabbitTemplate.execute(channel -> {
			declareExchanges(channel, exchanges.toArray(new Exchange[exchanges.size()]));
			declareQueues(channel, queues.toArray(new Queue[queues.size()]));
			declareBindings(channel, bindings.toArray(new Binding[bindings.size()]));
			return null;
		});
		this.logger.debug("Declarations finished");

	}

其中的代碼邏輯用於存放聲明的相關隊列、交換機和綁定關係。