实现延迟消息

接下来我们需要在SpringBoot中实现延迟消息功能，使用商品下单的场景。比如说有个用户下单了，他60分钟不支付订单，订单就会被取消，这就是一个典型的延迟消息使用场景

·首先我们需要在pom.xml文件中添加AMQP相关依赖
<!--消息队列相关依赖-->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-amqp</artifactId>
</dependency>
·之后在application.yml添加RabbitMQ的相关配置
spring:
  rabbitmq:
    host: localhost # rabbitmq的连接地址
    port: 5672 # rabbitmq的连接端口号
    virtual-host: /mall # rabbitmq的虚拟host
    username: mall # rabbitmq的用户名
    password: mall # rabbitmq的密码
    publisher-confirms: true #如果对异步消息需要回调必须设置为true
接下来创建RabbitMQ的Java配置，主要用于配置交换机、队列和绑定关系
/**
 * 消息队列配置
 */
@Configuration
public class RabbitMqConfig {

    /**
     * 订单延迟插件消息队列所绑定的交换机
     */
    @Bean
    CustomExchange  orderPluginDirect() {
        //创建一个自定义交换机，可以发送延迟消息
        Map<String, Object> args = new HashMap<>();
        args.put("x-delayed-type", "direct");
        return new CustomExchange(QueueEnum.QUEUE_ORDER_PLUGIN_CANCEL.getExchange(), "x-delayed-message",true, false,args);
    }

    /**
     * 订单延迟插件队列
     */
    @Bean
    public Queue orderPluginQueue() {
        return new Queue(QueueEnum.QUEUE_ORDER_PLUGIN_CANCEL.getName());
    }

    /**
     * 将订单延迟插件队列绑定到交换机
     */
    @Bean
    public Binding orderPluginBinding(CustomExchange orderPluginDirect,Queue orderPluginQueue) {
        return BindingBuilder
                .bind(orderPluginQueue)
                .to(orderPluginDirect)
                .with(QueueEnum.QUEUE_ORDER_PLUGIN_CANCEL.getRouteKey())
                .noargs();
    }

}
·创建一个取消订单消息的发出者，通过给消息设置x-delay头来设置消息从交换机发送到队列的延迟时间
/**
 * 取消订单消息的发出者
 */
@Component
public class CancelOrderSender {
    private static Logger LOGGER =LoggerFactory.getLogger(CancelOrderSender.class);
    @Autowired
    private AmqpTemplate amqpTemplate;

    public void sendMessage(Long orderId,final long delayTimes){
        //给延迟队列发送消息
        amqpTemplate.convertAndSend(QueueEnum.QUEUE_ORDER_PLUGIN_CANCEL.getExchange(), QueueEnum.QUEUE_ORDER_PLUGIN_CANCEL.getRouteKey(), orderId, new MessagePostProcessor() {
            @Override
            public Message postProcessMessage(Message message) throws AmqpException {
                //给消息设置延迟毫秒值
                message.getMessageProperties().setHeader("x-delay",delayTimes);
                return message;
            }
        });
        LOGGER.info("send delay message orderId:{}",orderId);
    }
}
·创建一个取消订单消息的接收者，用于处理订单延迟插件队列中的消息
/**
 * 取消订单消息的处理者
 */
@Component
@RabbitListener(queues = "mall.order.cancel.plugin")
public class CancelOrderReceiver {
    private static Logger LOGGER =LoggerFactory.getLogger(CancelOrderReceiver.class);
    @Autowired
    private OmsPortalOrderService portalOrderService;
    @RabbitHandler
    public void handle(Long orderId){
        LOGGER.info("receive delay message orderId:{}",orderId);
        portalOrderService.cancelOrder(orderId);
    }
}
·然后在我们的订单业务实现类中添加如下逻辑，当下单成功之前，往消息队列中发送一个取消订单的延迟消息，这样如果订单没有被支付的话，就能取消订单了
在这里插入代码片/**
 * 前台订单管理Service
 */
@Service
public class OmsPortalOrderServiceImpl implements OmsPortalOrderService {
    private static Logger LOGGER = LoggerFactory.getLogger(OmsPortalOrderServiceImpl.class);
    @Autowired
    private CancelOrderSender cancelOrderSender;

    @Override
    public CommonResult generateOrder(OrderParam orderParam) {
        //todo 执行一系类下单操作，具体参考mall项目
        LOGGER.info("process generateOrder");
        //下单完成后开启一个延迟消息，用于当用户没有付款时取消订单（orderId应该在下单后生成）
        sendDelayMessageCancelOrder(11L);
        return CommonResult.success(null, "下单成功");
    }

    @Override
    public void cancelOrder(Long orderId) {
        //todo 执行一系类取消订单操作，具体参考mall项目
        LOGGER.info("process cancelOrder orderId:{}",orderId);
    }

    private void sendDelayMessageCancelOrder(Long orderId) {
        //获取订单超时时间，假设为60分钟(测试用的30秒)
        long delayTimes = 30 * 1000;
        //发送延迟消息
        cancelOrderSender.sendMessage(orderId, delayTimes);
    }

}
·调用完成后查看控制台日志可以发现，从消息发送和消息接收处理正好相差了30s，我们设置的延迟时间
2020-06-08 13:46:01.474  INFO 1644 --- [nio-8080-exec-1] c.m.m.t.s.i.OmsPortalOrderServiceImpl    : process generateOrder
2020-06-08 13:46:01.482  INFO 1644 --- [nio-8080-exec-1] c.m.m.tiny.component.CancelOrderSender   : send delay message orderId:11
2020-06-08 13:46:31.517  INFO 1644 --- [cTaskExecutor-4] c.m.m.t.component.CancelOrderReceiver    : receive delay message orderId:11
2020-06-08 13:46:31.520  INFO 1644 --- [cTaskExecutor-4] c.m.m.t.s.i.OmsPortalOrderServiceImpl    : process cancelOrder orderId:11