Spring Cloud Stream POJO 来自/到 JSON 异常答案

【问题标题】：Spring Cloud Stream POJO from/to JSON ExceptionsSpring Cloud Stream POJO 来自/到 JSON 异常
【发布时间】：2016-11-29 07:18:31
【问题描述】：

我正在使用 Spring Cloud Stream。

在项目内部，我只想处理 Java 对象
对于 MQ（兔子），我希望消息的有效负载可以从 java 对象自动转换为 JSON 格式（这在未来是灵活的）。

但是当运行应用程序时，抛出异常...

所以输出通道配置为：

    output:
      destination: response
      contentType: application/json

输出和模型代码如下：

    /** Source method*/
    @Bean
    @ServiceActivator(outputChannel=Sink.OUTPUT)
    public MessageSource<String> timerReportMessageSource() {
        return new MessageSource<String>() {
            public Message<String> receive() {
                Response response = new Response(1, "response1");
                return new GenericMessage(response);
            }
        };
    }

    /** Model class */
    public class Response implements Serializable{
        public long id;
        public String name;
    }

异常信息：

    Caused by: org.springframework.messaging.MessageDeliveryException: failed to send Message to channel 'output'; nested exception is java.lang.IllegalArgumentException: payload must not be null
        at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:449) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:45) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:105) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutput(AbstractMessageProducingHandler.java:292) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractMessageProducingHandler.produceOutput(AbstractMessageProducingHandler.java:212) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutputs(AbstractMessageProducingHandler.java:129) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:115) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.dispatcher.AbstractDispatcher.tryOptimizedDispatch(AbstractDispatcher.java:116) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:148) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:121) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:77) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:45) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:105) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutput(AbstractMessageProducingHandler.java:292) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractMessageProducingHandler.produceOutput(AbstractMessageProducingHandler.java:212) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutputs(AbstractMessageProducingHandler.java:129) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:115) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.channel.FixedSubscriberChannel.send(FixedSubscriberChannel.java:70) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.channel.FixedSubscriberChannel.send(FixedSubscriberChannel.java:64) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:45) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:105) ~[spring-messaging-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.integration.endpoint.MessageProducerSupport.sendMessage(MessageProducerSupport.java:171) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.amqp.inbound.AmqpInboundChannelAdapter.access$400(AmqpInboundChannelAdapter.java:45) ~[spring-integration-amqp-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.amqp.inbound.AmqpInboundChannelAdapter$1.onMessage(AmqpInboundChannelAdapter.java:95) ~[spring-integration-amqp-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:777) ~[spring-rabbit-1.6.1.RELEASE.jar:na]
        ... 24 common frames omitted
    Caused by: java.lang.IllegalArgumentException: payload must not be null
        at org.springframework.util.Assert.notNull(Assert.java:115) ~[spring-core-4.3.2.RELEASE.jar:4.3.2.RELEASE]
        at org.springframework.integration.support.MutableMessage.<init>(MutableMessage.java:57) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.support.MutableMessage.<init>(MutableMessage.java:53) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.support.MutableMessageBuilder.withPayload(MutableMessageBuilder.java:86) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.support.MutableMessageBuilderFactory.withPayload(MutableMessageBuilderFactory.java:35) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.support.MutableMessageBuilderFactory.withPayload(MutableMessageBuilderFactory.java:26) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.cloud.stream.binding.MessageConverterConfigurer$ContentTypeConvertingInterceptor.preSend(MessageConverterConfigurer.java:194) ~[spring-cloud-stream-1.1.0.M1.jar:1.1.0.M1]
        at org.springframework.integration.channel.AbstractMessageChannel$ChannelInterceptorList.preSend(AbstractMessageChannel.java:538) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:415) ~[spring-integration-core-4.3.1.RELEASE.jar:4.3.1.RELEASE]
        ... 56 common frames omitted

所以我的问题是：

如果我想将 java 对象自动强制为 json，我是否错过了某些东西（配置...）？真的很感激。

【问题讨论】：

看起来我使用了错误的注释，应该是@StreamListerner insteadof @ServiceActivator

标签： java jackson rabbitmq messaging spring-cloud-stream

【解决方案1】：

null 消息有效负载表示未进行消息转换。根据您的配置，消息转换应该由MappingJackson2MessageConverter 进行。无论如何，您在类路径中没有那个，或者有一个自定义的MessageConverter 以某种方式返回null？

【讨论】：

谢谢，有样品或指南吗？

【解决方案2】：

首先，您的出站消息可能没有正确转换。通用代码不正确，其中有一些未经检查的强制转换：请在继续之前尝试此操作。

public MessageSource<Response> timerReportMessageSource() { return new MessageSource<Response>() { public Message<Response> receive() { Response response = new Response(1, "response1"); return new GenericMessage<>(response); } }; }

【讨论】：