如何通过 debezium CDC 机制反序列化从 kafka 代理收到的 BigDecimal 值？

Posted 2023-03-23

【中文标题】如何通过 debezium CDC 机制反序列化从 kafka 代理收到的 BigDecimal 值？

【英文标题】：How to deserialize BigDecimal value received from kafka broker through debezium CDC mechanism?

【发布时间】：2019-10-23 10:32:09

【问题描述】：

我有几个使用 Spring Boot 开发的微服务，每个都有自己的 Postgres 数据库。这些微服务通过 kafka broker 和 kafka connect 与 debezium 平台提供的 CDC 机制交换数据。我有一个微服务 A，它存储了一些具有 BigDecimal 属性的实体。另一个微服务 B 依赖于 A 存储的数据，因此它通过 kafka 主题作为消息获取数据，如下所示：

"after":"id":"267e8ba0-4986-447d-8328-315c839875c3","coefficient":"AZA=","created_at":1559950327672000,"label":"External Agent","updated_at":1559950327672000

系数属性是 BigDecimal，它作为 BigDecimal (4.00) 存储在微服务 A 数据库中。

4.00怎么会转成“AZA=”？ “AZA=”是某种编码格式来保持 BigDecimal 精度吗？如何再次从“AZA=”升级到 4.0？

请注意，jackson 无法将 "AZA=" 的字符串值反序列化为 BigDecimal 值，但以下情况除外：

com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `java.math.BigDecimal` from String "AZA=": not a valid representation
at [Source: (String)""id":"267e8ba0-4986-447d-8328-315c839875c3","coefficient":"AZA=","created_at":1559950327672000,"label":"External Agent","updated_at":1559950327672000"; line: 1, column: 60] (through reference chain: org.perfometer.performanceservice.entities.ActorTypeEntity["coefficient"])
at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67)
at com.fasterxml.jackson.databind.DeserializationContext.weirdStringException(DeserializationContext.java:1549)
at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdStringValue(DeserializationContext.java:911)
at com.fasterxml.jackson.databind.deser.std.NumberDeserializers$BigDecimalDeserializer.deserialize(NumberDeserializers.java:955)
at com.fasterxml.jackson.databind.deser.std.NumberDeserializers$BigDecimalDeserializer.deserialize(NumberDeserializers.java:922)
at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:288)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4013)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3004)
at org.perfometer.performanceservice.services.impl.ActorTypeServiceImpl.consumeActorTypeMessages(ActorTypeServiceImpl.java:123)
at org.perfometer.performanceservice.services.impl.ActorTypeServiceImpl$$FastClassBySpringCGLIB$$944d568c.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:749)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:295)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688)
at org.perfometer.performanceservice.services.impl.ActorTypeServiceImpl$$EnhancerBySpringCGLIB$$167173df.consumeActorTypeMessages(<generated>)
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:498)
at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:171)
at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:120)
at org.springframework.kafka.listener.adapter.HandlerAdapter.invoke(HandlerAdapter.java:48)
at org.springframework.kafka.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:283)
at org.springframework.kafka.listener.adapter.RecordMessagingMessageListenerAdapter.onMessage(RecordMessagingMessageListenerAdapter.java:79)
at org.springframework.kafka.listener.adapter.RecordMessagingMessageListenerAdapter.onMessage(RecordMessagingMessageListenerAdapter.java:50)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.doInvokeOnMessage(KafkaMessageListenerContainer.java:1263)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.invokeOnMessage(KafkaMessageListenerContainer.java:1256)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.doInvokeRecordListener(KafkaMessageListenerContainer.java:1217)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.doInvokeWithRecords(KafkaMessageListenerContainer.java:1198)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.invokeRecordListener(KafkaMessageListenerContainer.java:1118)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.invokeListener(KafkaMessageListenerContainer.java:933)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.pollAndInvoke(KafkaMessageListenerContainer.java:749)
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.run(KafkaMessageListenerContainer.java:698)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.lang.Thread.run(Thread.java:748)

任何提示或任何帮助将不胜感激！谢谢！

【参考方案1】：

这是 Java 的解决方案 - https://debezium.io/docs/faq/#how_to_retrieve_decimal_field_from_binary_representation

另外请查看decimal.handling.mode 选项以了解如何将BigDecimal 编码到消息中。

【参考方案2】：

如果您使用的是 Java 8，则可以将 Base64 字符串转换为字节数组，然后通过一些黑魔法得到一个 bigDecimal：

BigDecimal bigDecimal = new BigDecimal(new BigInteger(Base64.getDecoder().decode("BfXhAA==")), scale);

https://github.com/confluentinc/kafka-connect-storage-cloud/issues/48#issuecomment-395206864