扔AmqprejectanddontrequeueException后，RabbitMQ消息仍会重试

Question

我有一个简单的 Spring Boot应用程序在其中我有以下设置 RabbitMQ （Spring-Boot-Starter-Amqp版本为2.7.0）：

spring:
  rabbitmq:
    host: localhost
    port: 5672
    virtual-host: my_host
    username: admin
    password: password
    template:
      retry:
        enabled: true
        initial-interval: 3s
        max-interval: 10s
        multiplier: 2
        max-attempts: 3
    listener:
      simple:
        retry:
          enabled: true
          initial-interval: 3s
          max-interval: 10s
          multiplier: 2
          max-attempts: 3

a simpleererabbitlistenerconercontainerfactory < /code>使用 MessagePostProcessor ：

@Bean
public SimpleRabbitListenerContainerFactory myInterceptContainerFactory(final SimpleRabbitListenerContainerFactoryConfigurer configurer,
                                                                        final ConnectionFactory connectionFactory,
                                                                        final MyMessagePostProcessor myMessagePostProcessor) {
    SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory() {
        @Override
        protected void initializeContainer(SimpleMessageListenerContainer instance, RabbitListenerEndpoint endpoint) {
            instance.setAfterReceivePostProcessors(myMessagePostProcessor);
            super.initializeContainer(instance, endpoint);
        }
    };
    ((CachingConnectionFactory) connectionFactory).setRequestedHeartBeat(60);
    configurer.configure(factory, connectionFactory);
    return factory;
}

MessagePostProcessor 非常简单，如果版本错误在标题中，它会抛出 AmqPrejectAndDontrequeueException ：

@Component
public class MyMessagePostProcessor implements MessagePostProcessor {

    private static final Logger LOGGER = LogManager.getLogger(MyMessagePostProcessor.class);

    @Override
    public Message postProcessMessage(Message message) throws AmqpException {
        if (!"1.0".equalsIgnoreCase(message.getMessageProperties().getHeader("version"))) {
            LOGGER.error("wrong version");
            throw new AmqpRejectAndDontRequeueException("wrong version");
        }
        return message;
    }

}

当我发送带有错误版本的消息时，它基于日志正常工作：

MyApp: 2022-07-05 15:49:33,675 ERROR [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#0-1] c.g.r.a.q.p.MyMessagePostProcessor:22 - wrong version
MyApp: 2022-07-05 15:49:33,676  WARN [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#0-1] o.s.a.r.l.ConditionalRejectingErrorHandler:169 - Execution of Rabbit message listener failed.
org.springframework.amqp.AmqpRejectAndDontRequeueException: wrong version
    at com.my.app.queue.postprocess.MyMessagePostProcessor.postProcessMessage(MyMessagePostProcessor.java:23) ~[classes/:1.0.0]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doExecuteListener(AbstractMessageListenerContainer.java:1544) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.executeListener(AbstractMessageListenerContainer.java:1499) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.doReceiveAndExecute(SimpleMessageListenerContainer.java:992) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.receiveAndExecute(SimpleMessageListenerContainer.java:939) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$1600(SimpleMessageListenerContainer.java:84) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.mainLoop(SimpleMessageListenerContainer.java:1316) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:1222) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at java.lang.Thread.run(Thread.java:833) ~[?:?]

我的消费者仅执行一个错误log，并立即投掷 amqpreject和DontrequequeueException 查看该消息是否没有重试的无生气者队列：

@Component
public class MyMessageConsumer {
    private static final Logger LOGGER = LogManager.getLogger(MyMessageConsumer.class);

    @RabbitListener(queues = "my.queue", containerFactory = "myInterceptContainerFactory")
    public void consumerMessage() {
        LOGGER.error("error in consuming message");
        throw new AmqpRejectAndDontRequeueException("over");
    }

}

但基于日志，它清楚地看到了重试3次（因为我的错误日志被打印了3次），只有在此之后，该消息才传递到无聊的队列中：

MyApp: 2022-07-05 15:50:32,182 ERROR [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#0-1] c.g.r.a.q.c.MyMessageConsumer:23 - error in consuming message
MyApp: 2022-07-05 15:50:46,603 ERROR [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#0-1] c.g.r.a.q.c.MyMessageConsumer:23 - error in consuming message
MyApp: 2022-07-05 15:50:52,617 ERROR [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#0-1] c.g.r.a.q.c.MyMessageConsumer:23 - error in consuming message
MyApp: 2022-07-05 15:50:52,618  WARN [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#0-1] o.s.a.r.r.RejectAndDontRequeueRecoverer:74 - Retries exhausted for message (Body:'[B@4060893b(byte[75])' MessageProperties [headers={version=1.0, requestor=MyApp}, contentLength=0, receivedDeliveryMode=NON_PERSISTENT, redelivered=false, receivedExchange=, receivedRoutingKey=my.queue, deliveryTag=2, consumerTag=amq.ctag-5Xx6EwwjVokRV6wD9xL8Og, consumerQueue=my.queue])
org.springframework.amqp.rabbit.support.ListenerExecutionFailedException: Listener method 'public void com.my.app.queue.consumer.MyMessageConsumer.retrieveNcid()' threw exception
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:271) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandlerAndProcessResult(MessagingMessageListenerAdapter.java:208) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.onMessage(MessagingMessageListenerAdapter.java:147) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:1657) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.actualInvokeListener(AbstractMessageListenerContainer.java:1576) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.retry.interceptor.RetryOperationsInterceptor$1.doWithRetry(RetryOperationsInterceptor.java:97) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:329) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:225) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.interceptor.RetryOperationsInterceptor.invoke(RetryOperationsInterceptor.java:122) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.amqp.rabbit.listener.$Proxy187.invokeListener(Unknown Source) ~[?:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.invokeListener(AbstractMessageListenerContainer.java:1564) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doExecuteListener(AbstractMessageListenerContainer.java:1555) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.executeListener(AbstractMessageListenerContainer.java:1499) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.doReceiveAndExecute(SimpleMessageListenerContainer.java:992) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.receiveAndExecute(SimpleMessageListenerContainer.java:939) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$1600(SimpleMessageListenerContainer.java:84) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.mainLoop(SimpleMessageListenerContainer.java:1316) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:1222) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at java.lang.Thread.run(Thread.java:833) ~[?:?]
Caused by: org.springframework.amqp.AmqpRejectAndDontRequeueException: over
    at com.my.app.queue.consumer.MyMessageConsumer.retrieveNcid(MyMessageConsumer.java:24) ~[classes/:1.0.0]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:169) ~[spring-messaging-5.3.20.jar:5.3.20]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:119) ~[spring-messaging-5.3.20.jar:5.3.20]
    at org.springframework.amqp.rabbit.listener.adapter.HandlerAdapter.invoke(HandlerAdapter.java:75) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:262) ~[spring-rabbit-2.4.5.jar:2.4.5]
    ... 27 more
MyApp: 2022-07-05 15:50:52,620  WARN [org.springframework.amqp.rabbit.RabbitListenerEndpointContainer#0-1] o.s.a.r.l.ConditionalRejectingErrorHandler:169 - Execution of Rabbit message listener failed.
org.springframework.amqp.rabbit.support.ListenerExecutionFailedException: Retry Policy Exhausted
    at org.springframework.amqp.rabbit.retry.RejectAndDontRequeueRecoverer.recover(RejectAndDontRequeueRecoverer.java:76) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.config.StatelessRetryOperationsInterceptorFactoryBean.recover(StatelessRetryOperationsInterceptorFactoryBean.java:77) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.retry.interceptor.RetryOperationsInterceptor$ItemRecovererCallback.recover(RetryOperationsInterceptor.java:157) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.support.RetryTemplate.handleRetryExhausted(RetryTemplate.java:539) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:387) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:225) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.interceptor.RetryOperationsInterceptor.invoke(RetryOperationsInterceptor.java:122) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.amqp.rabbit.listener.$Proxy187.invokeListener(Unknown Source) ~[?:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.invokeListener(AbstractMessageListenerContainer.java:1564) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doExecuteListener(AbstractMessageListenerContainer.java:1555) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.executeListener(AbstractMessageListenerContainer.java:1499) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.doReceiveAndExecute(SimpleMessageListenerContainer.java:992) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.receiveAndExecute(SimpleMessageListenerContainer.java:939) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$1600(SimpleMessageListenerContainer.java:84) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.mainLoop(SimpleMessageListenerContainer.java:1316) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:1222) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at java.lang.Thread.run(Thread.java:833) ~[?:?]
Caused by: org.springframework.amqp.AmqpRejectAndDontRequeueException
    ... 19 more
Caused by: org.springframework.amqp.rabbit.support.ListenerExecutionFailedException: Listener method 'public void com.my.app.queue.consumer.MyMessageConsumer.retrieveNcid()' threw exception
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:271) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandlerAndProcessResult(MessagingMessageListenerAdapter.java:208) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.onMessage(MessagingMessageListenerAdapter.java:147) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:1657) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.actualInvokeListener(AbstractMessageListenerContainer.java:1576) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.retry.interceptor.RetryOperationsInterceptor$1.doWithRetry(RetryOperationsInterceptor.java:97) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:329) ~[spring-retry-1.3.3.jar:?]
    ... 14 more
Caused by: org.springframework.amqp.AmqpRejectAndDontRequeueException: over
    at com.my.app.queue.consumer.MyMessageConsumer.retrieveNcid(MyMessageConsumer.java:24) ~[classes/:1.0.0]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:169) ~[spring-messaging-5.3.20.jar:5.3.20]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:119) ~[spring-messaging-5.3.20.jar:5.3.20]
    at org.springframework.amqp.rabbit.listener.adapter.HandlerAdapter.invoke(HandlerAdapter.java:75) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:262) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandlerAndProcessResult(MessagingMessageListenerAdapter.java:208) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.onMessage(MessagingMessageListenerAdapter.java:147) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:1657) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.actualInvokeListener(AbstractMessageListenerContainer.java:1576) ~[spring-rabbit-2.4.5.jar:2.4.5]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.20.jar:5.3.20]
    at org.springframework.retry.interceptor.RetryOperationsInterceptor$1.doWithRetry(RetryOperationsInterceptor.java:97) ~[spring-retry-1.3.3.jar:?]
    at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:329) ~[spring-retry-1.3.3.jar:?]
    ... 14 more

但是我想将消息传递到无需重试3次的情况下将消息传递到无用的队列中。

我猜 LinereXecutionFailedException：重试策略用尽，但我不明白为什么我的 amqprejectAnddontrequeueexception 包裹在此例外，因为我的 message> MessagePostProcessor 不抛出 listererexecutionfailedexception ，只是我投入代码的那个。

我在这里想念什么？

Answer 1

正如@gary Russel所建议的那样，我修改了以下重试策略：

@Bean
public RabbitRetryTemplateCustomizer customizeRetryPolicy(@Value("${spring.rabbitmq.listener.simple.retry.max-attempts}") int maxAttempts) {
    SimpleRetryPolicy policy = new SimpleRetryPolicy(maxAttempts, Map.of(AmqpRejectAndDontRequeueException.class, false), true, true);
    return (target, retryTemplate) -> retryTemplate.setRetryPolicy(policy);
}

仅配置此新豆，一切都按预期工作！

Answer 2

在重新恢复耗尽之前，容器对例外情况一无所知。

您需要自定义重试策略，以免为该例外重试。

目前使用应用程序属性是不可能的。您需要将重试拦截器配置为bean并将其注入容器工厂。

如果您需要帮助，我可以添加一个示例。