5.RabbitMQ系列之headers交换器

headers exchange是根据消息header值而不是routing key将消息路由到队列的交换器。
生产者在消息头中以键值对的形式添加一些值，并将其发送到headers exchange,
收到消息后，headers exchange尝试将所有或任何（基于x-match的值）header值与绑定到它的所有队列的值匹配。 如果找到匹配，则将消息路由到绑定值匹配的队列，如果未找到匹配，则忽略该消息

1. 完整示例代码

• 编写HeaderExchangeConfig.java配置文件，已声明headers exchange及其绑定

@Configuration
public class HeaderExchangeConfig {

    @Bean
    public HeadersExchange headers() {
        return new HeadersExchange("headers");
    }

    private static class ConsumerConfig {

        @Bean
        public Queue headersAutoDeleteQueue1() {
            return new AnonymousQueue();
        }

        @Bean
        public Queue headersAutoDeleteQueue2() {
            return new AnonymousQueue();
        }

        @Bean
        public Queue headersAutoDeleteQueue3() {
            return new AnonymousQueue();
        }

        @Bean
        public Binding headersBinding1(HeadersExchange headers, Queue headersAutoDeleteQueue1) {
            Map<String, Object> headerMap = new HashMap<>();
            headerMap.put("h1", "Header1");
            headerMap.put("h2", "Header2");
            /**
             * 匹配到任意一个就发送至队列
             */
            return BindingBuilder.bind(headersAutoDeleteQueue1).to(headers).whereAny(headerMap).match();
        }

        @Bean
        public Binding headersBinding2(HeadersExchange headers, Queue headersAutoDeleteQueue2) {
            Map<String, Object> headerMap = new HashMap<>();
            headerMap.put("h1", "Header1");
            headerMap.put("h2", "Header2");
            /**
             * 全部匹配到才会发送至队列
             */
            return BindingBuilder.bind(headersAutoDeleteQueue2).to(headers).whereAll(headerMap).match();
        }

        @Bean
        public Binding headersBinding3(HeadersExchange headers, Queue headersAutoDeleteQueue3) {
            /**
             * 匹配到任意一个就发送至队列， 此处与headersBinding1一致，为了证明其也有fanout模式的功能
             */
            Map<String, Object> headerMap = new HashMap<>();
            headerMap.put("h1", "Header1");
            headerMap.put("h2", "Header2");
            return BindingBuilder.bind(headersAutoDeleteQueue3).to(headers).whereAny(headerMap).match();
        }
    }
}

• 编写生产者

@Component
public class HeaderSender {

    private RabbitMessagingTemplate rabbitMessagingTemplate;

    public HeaderSender(RabbitMessagingTemplate rabbitMessagingTemplate) {
        this.rabbitMessagingTemplate = rabbitMessagingTemplate;
    }

    public void send() {
        String msg = "Hello World!";
        Map<String, Object> headerMap = new HashMap<>();
        headerMap.put("h1", "Header1");
        headerMap.put("h3", "Header3");
        rabbitMessagingTemplate.convertAndSend("headers", "", msg, headerMap);

        msg = "My Girl!";
        headerMap.clear();
        headerMap.put("h1", "Header1");
        headerMap.put("h2", "Header2");
        rabbitMessagingTemplate.convertAndSend("headers", "", msg, headerMap);
    }
}

• 编写消费者

@Component
public class HeaderReceiver {

    @RabbitListener(queues = "#{headersAutoDeleteQueue1.name}")
    public void receive1(String in) {
        System.out.println("临时队列1接收到消息:" + in);
    }

    @RabbitListener(queues = "#{headersAutoDeleteQueue2.name}")
    public void receive2(String in) {
        System.out.println("临时队列2接收到消息:" + in);
    }

    @RabbitListener(queues = "#{headersAutoDeleteQueue3.name}")
    public void receive3(String in) {
        System.out.println("临时队列3接收到消息:" + in);
    }
}

• 编写测试方法

@SpringBootTest
public class RabbitTest {
    @Autowired
    private HeaderSender headerSender;

    @Test
    public void testHeaderSender() {
        headerSender.send();
    }
}

从结果中不难看出，My Girl消息3个队列都匹配到headers, 而Hello Word消息只有队列1与3匹配到，毕竟他没有h2头啦

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