object-to-json-transformer: ClassCastException: [B cannot be cast to java.lang.String

[serff]

Hey everyone, I'm stumped on why this is happening, so hoping you all can help out. I have two different applications set up using SI and RabbitMQ to send messages along a pipeline. I have an object that gets turned into json using the object-to-json transformer. The messages go into the queue and the next application picks them up and then the object-to-json transformer pukes and can't transform the object. It says the object is a byte array ([B), but in the logging, it is clearly a string even with a content type of application/json. So I don't get what is happening. Here is the stack trace:

WARN : SimpleAsyncTaskExecutor-1 org.springframework.amqp.rabbit.config.StatelessRetryOperationsInterceptorFactoryBean - Message dropped on recovery: (Body:'{"id":null,"source":"USER","details":"test ","summary":null,"title":"Test","effectiveDate":1359010800000,"expirationDate":1359097200000,"messageType":"ALERT","messageStatus":null,"messageUrgency":null,"messageSeverity":null,"messageCertainty":null,"areas":[ ... ],"sourceId":null,"alertType":"User Generated"}'; ID:null; Content:application/json; Headers:{content-type=application/json}; Exchange:; RoutingKey:messages; Reply:null; DeliveryMode:PERSISTENT; DeliveryTag:1)
org.springframework.amqp.rabbit.listener.ListenerExecutionFailedException: Listener threw exception
	at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.wrapToListenerExecutionFailedExceptionIfNeeded(AbstractMessageListenerContainer.java:647)
	at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:586)
	at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.invokeListener(AbstractMessageListenerContainer.java:482)
	at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$001(SimpleMessageListenerContainer.java:58)
	at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$1.invokeListener(SimpleMessageListenerContainer.java:107)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
	at org.springframework.retry.interceptor.RetryOperationsInterceptor$1.doWithRetry(RetryOperationsInterceptor.java:69)
	at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:255)
	at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:162)
	at org.springframework.retry.interceptor.RetryOperationsInterceptor.invoke(RetryOperationsInterceptor.java:87)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
	at $Proxy12.invokeListener(Unknown Source)
	at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.invokeListener(SimpleMessageListenerContainer.java:608)
	at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.executeListener(AbstractMessageListenerContainer.java:454)
	at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.doReceiveAndExecute(SimpleMessageListenerContainer.java:471)
	at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.receiveAndExecute(SimpleMessageListenerContainer.java:455)
	at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$300(SimpleMessageListenerContainer.java:58)
	at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:548)
	at java.lang.Thread.run(Thread.java:662)
Caused by: org.springframework.integration.transformer.MessageTransformationException: failed to transform message
	at org.springframework.integration.transformer.AbstractTransformer.transform(AbstractTransformer.java:44)
	at org.springframework.integration.transformer.MessageTransformingHandler.handleRequestMessage(MessageTransformingHandler.java:67)
	at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:134)
	at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:73)
	at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:115)
	at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:102)
	at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:77)
	at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:157)
	at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:128)
	at org.springframework.integration.core.MessagingTemplate.doSend(MessagingTemplate.java:288)
	at org.springframework.integration.core.MessagingTemplate.send(MessagingTemplate.java:149)
	at org.springframework.integration.endpoint.MessageProducerSupport.sendMessage(MessageProducerSupport.java:92)
	at org.springframework.integration.amqp.inbound.AmqpInboundChannelAdapter.access$200(AmqpInboundChannelAdapter.java:41)
	at org.springframework.integration.amqp.inbound.AmqpInboundChannelAdapter$1.onMessage(AmqpInboundChannelAdapter.java:76)
	at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:584)
	... 24 more
Caused by: java.lang.ClassCastException: [B cannot be cast to java.lang.String
	at org.springframework.integration.json.JsonToObjectTransformer.transformPayload(JsonToObjectTransformer.java:30)
	at org.springframework.integration.transformer.AbstractPayloadTransformer.doTransform(AbstractPayloadTransformer.java:33)
	at org.springframework.integration.transformer.AbstractTransformer.transform(AbstractTransformer.java:33)
	... 38 more

Here is the spring config for the receiving end of the application:

<context:annotation-config />
    <mvc:annotation-driven/>

    <si:logging-channel-adapter id="logger" level="DEBUG"/>
    
    <!-- All the messages come from the Messages rabbit queue -->
    <rabbit:queue name="messages"/>
    <amqp:inbound-channel-adapter channel="messagesIn"
                                  connection-factory="rabbitConnectionFactory"
                                  queue-names="messages"
                                  advice-chain="retryInterceptor" />
                                      
    <si:channel id="messageChannel">
        <si:interceptors>
            <si:wire-tap channel="logger"/>
        </si:interceptors>
    </si:channel>
    <si:json-to-object-transformer input-channel="messagesIn" output-channel="messageChannel" type="com.mycompany.model.Message"/>
    
    <bean id="messageHandler" class="com.mycompany.MessageConsumer"/>
    <si:service-activator input-channel="messageChannel" ref="messageHandler"/>

I'm using Spring Integration 2.2.0.RELEASE. Funny thing is this all used to work. I think I might have upgraded to 2.2 at some point and they may have been when it broke...but I'm not sure...

Please help! Thanks!

[Gary Russell]

This is due to a change in 2.2.

http://static.springsource.org/sprin...ml#2.2-o-t-j-t

Please see the "Important" note here...

http://static.springsource.org/sprin...ml#transformer

(Scroll down to JSON Transformers).

There's a simple configuration change you need to make.

[Gary Russell]

It is also mentioned in the 2.1 to 2.2 migration guide...

https://github.com/SpringSource/spri...igration-Guide

[serff]

THANK YOU! That is exactly what it was. Next time, I'll try to make sure I read those migration guides more carefully...