• @RabbitListener默认是单线程监听队列(@RabbitListener(queues = {MqConstants.OA_TAB_REFRESH}, concurrency = "10") 也能实现十个并发)
• 缺点 : 单线程处理消息, 当消息队列有多个任务时消费端监听队列每次只消费一个消息 , 容易引起消息堆积 , 处理效率慢…
• 解决方法 : 多线程处理消息 , 配置mq容器工厂参数 , 增加并发处理量 .

@Configuration
public class RabbitMQConfig {
    public static final String QUEUE_INFORM_EMAIL = "queue_inform_email";
    // 声明交换机
    // 声明队列
    // 队列绑定交换机,指定routingKey
	...
	//并发数量
	public static final int DEFAULT_CONCURRENT = 10;
	@Bean("customContainerFactory")
	public SimpleRabbitListenerContainerFactory containerFactory(SimpleRabbitListenerContainerFactoryConfigurer configurer, 
		ConnectionFactory connectionFactory) {
   		SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
   		factory.setConcurrentConsumers(DEFAULT_CONCURRENT);
   		factory.setMaxConcurrentConsumers(DEFAULT_CONCURRENT);
  		configurer.configure(factory, connectionFactory);
   		return factory;
 	}
 }

@Component
public class ReceiveHandler {
    private static final Logger LOGGER = LoggerFactory.getLogger(ReceiveHandler.class);
    // 在@RabbitListener注解中指定容器工厂
    @RabbitListener(queues = {RabbitmqConfig.QUEUE_INFORM_EMAIL},
                    containerFactory = "customContainerFactory")
   //@RabbitListener(queues = {MqConstants.OA_TAB_REFRESH}, concurrency = "10") 也能实现十个并发
    public void send_email(String msg,Message message,Channel channel){
        LOGGER.info("receive message is:"+msg);
        // work
        ...
    }
}