org.springframework.messaging.converter.MessageConversionException:Could not read JSON: Cannot const
org.springframework.messaging.converter.MessageConversionException: Could not read JSON: Cannot construct instance of `com.example.mqtest.mq.User` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
at [Source: (byte[])"{"name":"哈哈"}"; line: 1, column: 2]; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `com.example.mqtest.mq.User` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
at [Source: (byte[])"{"name":"哈哈"}"; line: 1, column: 2], failedMessage=GenericMessage [payload=byte[17], headers={amqp_receivedDeliveryMode=PERSISTENT, amqp_receivedExchange=comment, amqp_deliveryTag=1, deliveryAttempt=3, amqp_consumerQueue=comment.comment_like_group111, amqp_redelivered=false, amqp_receivedRoutingKey=comment_like, amqp_timestamp=Fri Mar 27 13:36:57 CST 2020, amqp_messageId=c04aa17c-ae7b-2ca2-1ed1-2d623cc45409, id=3e6f1fc8-00c1-3e93-d6e6-c09c83cf31dc, amqp_consumerTag=amq.ctag-22vW4PCiDJzGNiE5QGjfwQ, sourceData=(Body:'{"name":"哈哈"}' MessageProperties [headers={}, timestamp=Fri Mar 27 13:36:57 CST 2020, messageId=c04aa17c-ae7b-2ca2-1ed1-2d623cc45409, contentType=application/json, contentLength=0, receivedDeliveryMode=PERSISTENT, priority=0, redelivered=false, receivedExchange=comment, receivedRoutingKey=comment_like, deliveryTag=1, consumerTag=amq.ctag-22vW4PCiDJzGNiE5QGjfwQ, consumerQueue=comment.comment_like_group111]), contentType=application/json, timestamp=1585287417722}]
at org.springframework.messaging.converter.MappingJackson2MessageConverter.convertFromInternal(MappingJackson2MessageConverter.java:235)
at org.springframework.cloud.stream.converter.ApplicationJsonMessageMarshallingConverter.convertFromInternal(ApplicationJsonMessageMarshallingConverter.java:112)
at org.springframework.messaging.converter.AbstractMessageConverter.fromMessage(AbstractMessageConverter.java:197)
at org.springframework.messaging.converter.CompositeMessageConverter.fromMessage(CompositeMessageConverter.java:70)
at org.springframework.cloud.stream.config.SmartPayloadArgumentResolver.resolveArgument(SmartPayloadArgumentResolver.java:115)
at org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:117)
at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:148)
at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:116)
at org.springframework.cloud.stream.binding.StreamListenerMessageHandler.handleRequestMessage(StreamListenerMessageHandler.java:55)
at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:127)
at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:177)
at org.springframework.integration.dispatcher.AbstractDispatcher.tryOptimizedDispatch(AbstractDispatcher.java:115)
at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:133)
at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:106)
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:73)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:453)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:403)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:187)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:166)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:47)
at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:109)
at org.springframework.integration.endpoint.MessageProducerSupport.sendMessage(MessageProducerSupport.java:198)
at org.springframework.integration.amqp.inbound.AmqpInboundChannelAdapter.access$1300(AmqpInboundChannelAdapter.java:61)
at org.springframework.integration.amqp.inbound.AmqpInboundChannelAdapter$Listener.lambda$onMessage$0(AmqpInboundChannelAdapter.java:239)
at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:287)
at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:180)
at org.springframework.integration.amqp.inbound.AmqpInboundChannelAdapter$Listener.onMessage(AmqpInboundChannelAdapter.java:236)
at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:1579)
at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.actualInvokeListener(AbstractMessageListenerContainer.java:1498)
at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.invokeListener(AbstractMessageListenerContainer.java:1486)
at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doExecuteListener(AbstractMessageListenerContainer.java:1477)
at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.executeListener(AbstractMessageListenerContainer.java:1421)
at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.doReceiveAndExecute(SimpleMessageListenerContainer.java:963)
at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.receiveAndExecute(SimpleMessageListenerContainer.java:913)
at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$1600(SimpleMessageListenerContainer.java:81)
at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.mainLoop(SimpleMessageListenerContainer.java:1284)
at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:1190)
at java.lang.Thread.run(Thread.java:748)
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `com.example.mqtest.mq.User` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
at [Source: (byte[])"{"name":"哈哈"}"; line: 1, column: 2]
at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1429)
at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1059)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1297)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:326)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4202)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3300)
at org.springframework.messaging.converter.MappingJackson2MessageConverter.convertFromInternal(MappingJackson2MessageConverter.java:219)
... 37 more在使用springboot stream rabbitmq时候 新建了项目，配置好后发送对象消息到mq
然后报了如上错误，进行代码跟踪了下。发现无法解析User类，因为user类使用的lombok注解，模型如下
import lombok.Data;
import java.io.Serializable;
@Data
public class User implements Serializable {
private String name;
public User(String name) {
this.name = name;
}
}
因为给了有属性的构造函数，没有指定出空的构造，所以mq处理的方法拿到class处理没法拿到对象的句柄地址，也没法进行序列化操作
，解决办法是加了个默认的空构造进去，当然你没有有参构造是不用加空默认的
import lombok.Data;
import java.io.Serializable;
@Data
public class User implements Serializable {
private String name;
public User() {
}
public User(String name) {
this.name = name;
}
}
重启项目运行，发送与接收都是正常的了
其实出现问题我们要多读读异常信息，最好能跟进去看下，因为情况不同，所以光靠搜索出来的答案不一定使用，希望大家能理解异常，跟进源码，静下心来分析一下string