springboot+rabbitmq 之 消费端配置

Chapter1

直接上代码：

@Slf4j
@Component
public class UserSettlementConsumer {

    @RabbitHandler
    @RabbitListener(queues = "${spring.rabbitmq.mq-name}")
    public void testListener(String msg) {
        log.info("消息出队:"+msg);
    }
}

 可以看出来，RabbitMQ主要是借助于@RabbitHandler和@RabbitListener这两个注解来实现消息队列的消费。

@RabbitHandler的javadoc注释：Annotation that marks a method to be the target of a Rabbit message listener within a class that is annotated with RabbitListener.
@RabbitListener的javadoc注释：Annotation that marks a method to be the target of a Rabbit message listener on the specified queues() (or bindings()).

Chapter2

需要说明的是，在应用程序服务启动时，如果指定的消息在broker中不存在，则会导致mq初始化失败，服务也无法启动。错误信息：channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no queue 'test.queue' in vhost '/', class-id=50, method-id=10)

如下是详细的错误信息：

2021-06-15 15:13:14.997 [][] [main] INFO  o.s.a.rabbit.connection.CachingConnectionFactory:497 - Created new connection: connectionFactory#53ea380b:0/SimpleConnection@5b1cedfd [delegate=amqp://rabbitadmin@192.168.40.20:5672/, localPort= 1142]
2021-06-15 15:13:15.155 [][] [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#3-1] WARN  o.s.amqp.rabbit.listener.BlockingQueueConsumer:707 - Failed to declare queue: test.queue
2021-06-15 15:13:15.155 [][] [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#3-1] WARN  o.s.amqp.rabbit.listener.BlockingQueueConsumer:641 - Queue declaration failed; retries left=3
org.springframework.amqp.rabbit.listener.BlockingQueueConsumer$DeclarationException: Failed to declare queue(s):[test.queue]
    at org.springframework.amqp.rabbit.listener.BlockingQueueConsumer.attemptPassiveDeclarations(BlockingQueueConsumer.java:713)
    at org.springframework.amqp.rabbit.listener.BlockingQueueConsumer.passiveDeclarations(BlockingQueueConsumer.java:597)
    at org.springframework.amqp.rabbit.listener.BlockingQueueConsumer.start(BlockingQueueConsumer.java:584)
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.initialize(SimpleMessageListenerContainer.java:1338)
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:1183)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: null
    at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:126)
    at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:122)
    at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:144)
    at com.rabbitmq.client.impl.ChannelN.queueDeclarePassive(ChannelN.java:1006)
    at com.rabbitmq.client.impl.ChannelN.queueDeclarePassive(ChannelN.java:52)
    at org.springframework.amqp.rabbit.connection.PublisherCallbackChannelImpl.queueDeclarePassive(PublisherCallbackChannelImpl.java:363)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.amqp.rabbit.connection.CachingConnectionFactory$CachedChannelInvocationHandler.invoke(CachingConnectionFactory.java:1190)
    at com.sun.proxy.$Proxy252.queueDeclarePassive(Unknown Source)
    at org.springframework.amqp.rabbit.listener.BlockingQueueConsumer.attemptPassiveDeclarations(BlockingQueueConsumer.java:692)
    ... 5 common frames omitted
Caused by: com.rabbitmq.client.ShutdownSignalException: channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no queue 'test.queue' in vhost '/', class-id=50, method-id=10)
    at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:66)
    at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:36)
    at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:494)
    at com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:288)
    at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:138)
    ... 15 common frames omitted

错误描述很明显，是要求指定的队列必须存在。

解决办法有2个：

• 一是利用@Bean注解来声明queue。
• 二是借助于@RabbitListener的成员：queuesToDeclare

@Bean声明方式如下：

@Configuration
public class DirectRabbitConfig {

    @Value("${spring.rabbitmq.mq-name}")
    private String mqName;

    @Bean
    public Queue myQueue() {
        return new Queue(mqName, true);
    }
}

org.springframework.amqp.rabbit.annotation.RabbitListener#queuesToDeclare 可以在队列不存在时直接创建：

@Slf4j
@Component
public class UserSettlementConsumer {

    @RabbitHandler
    @RabbitListener(queuesToDeclare ={@Queue(name = "${spring.rabbitmq.mq-name}",durable = "true")})
    public void testListener(String msg) {
        log.info("消息出队:"+msg);
    }
}

 如下是spring-rabbit-2.2.0.RELEASE.jar里org.springframework.amqp.rabbit.annotation.RabbitListener#queuesToDeclare的javadoc：

package org.springframework.amqp.rabbit.annotation;
public @interface RabbitListener {

    /**
     * The queues for this listener.
     * If there is a {@link org.springframework.amqp.rabbit.core.RabbitAdmin} in the
     * application context, the queue will be declared on the broker with default
     * binding (default exchange with the queue name as the routing key).
     * Mutually exclusive with {@link #bindings()} and {@link #queues()}.
     * @return the queue(s) to declare.
     * @see org.springframework.amqp.rabbit.listener.MessageListenerContainer
     * @since 2.0
     */
    Queue[] queuesToDeclare() default {};

}

Chapter3

回过头来介绍RabbitListener#queues()

package org.springframework.amqp.rabbit.annotation;
public @interface RabbitListener {

    /**
     * The queues for this listener.
     * The entries can be 'queue name', 'property-placeholder keys' or 'expressions'.
     * Expression must be resolved to the queue name or {@code Queue} object.
     * The queue(s) must exist, or be otherwise defined elsewhere as a bean(s) with
     * a {@link org.springframework.amqp.rabbit.core.RabbitAdmin} in the application
     * context.
     * Mutually exclusive with {@link #bindings()} and {@link #queuesToDeclare()}.
     * @return the queue names or expressions (SpEL) to listen to from target
     * @see org.springframework.amqp.rabbit.listener.MessageListenerContainer
     */
    String[] queues() default {};

}

从以上RabbitListener#queues()的javadoc内容可以看出来如下三点信息，其中第2条指明了队列必须存在：

1. queues的取值可以是常量（如 MessageQueueConstant.USER_QUEUE），可以是属性占位符（如 "${spring.rabbitmq.mq-name}"），可以是SpEL表达式（如 "#{configToolkitProp['zk.address']}"、"#{userQueue.name}"）
2. 所指定的队列必须存在，或者是ApplicationContext里的一个具有org.springframework.amqp.rabbit.core.RabbitAdmin的bean。
3. queues()与bindings()和queuesToDeclare()是互斥的。设定了queues()，就不能再设定bindings()和queuesToDeclare()了。

Chapter4

在服务运行过程中，如果broker里的交换机或队列被删掉了，同样会导致无法生产消息。如下是错误信息。这时，只能重启服务或者手动在broker里创建所需的交换机和队列。
2021-06-17 15:13:18.782 [AMQP Connection 192.168.40.20:5672] ERROR o.s.a.rabbit.connection.CachingConnectionFactory:1468 - Channel shutdown: channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no exchange 'test-USER_SETTLEMENT_EXCHANGE' in vhost '/', class-id=60, method-id=40)