ClassCastException with the latest snapshot build

Getting the following when having key as string. Was working well till last week. However, today first had to upgrade the dependency on spring-kafka to 2.1.3.BUILD-SNAPSHOT (as the empty constructor was StreamFactoryBean was not there in 2.1.2-RELEASE). Once this was resolved, started to get this error.

tried setting:

spring.cloud.stream.bindings.input.consumer.key.deserializer: org.apache.kafka.common.serialization.StringDeserializer

spring.cloud.stream.kstream.bindings.output.producer.keySerde: org.apache.kafka.common.serialization.Serdes$StringSerde

however, they were not getting set (seen in the spring-boot startup logs).

I think this is related to changes in KStreamListenerSetupMethodOrchestrator.java

Exception in thread "eventMetricRecorder-73aa1b44-a9bf-4087-9ccc-39b32f145d69-StreamThread-1" java.lang.ClassCastException: [B cannot be cast to java.lang.String at org.apache.kafka.streams.kstream.internals.KStreamMap$KStreamMapProcessor.process(KStreamMap.java:41) at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:46) at org.apache.kafka.streams.processor.internals.StreamsMetricsImpl.measureLatencyNs(StreamsMetricsImpl.java:208) at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:124) at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:85) at org.apache.kafka.streams.kstream.internals.KStreamMap$KStreamMapProcessor.process(KStreamMap.java:42) at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:46) at org.apache.kafka.streams.processor.internals.StreamsMetricsImpl.measureLatencyNs(StreamsMetricsImpl.java:208) at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:124) at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:85) at org.apache.kafka.streams.kstream.internals.KStreamPassThrough$KStreamPassThroughProcessor.process(KStreamPassThrough.java:33) at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:46) at org.apache.kafka.streams.processor.internals.StreamsMetricsImpl.measureLatencyNs(StreamsMetricsImpl.java:208) at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:124) at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:99) at org.apache.kafka.streams.kstream.internals.KStreamBranch$KStreamBranchProcessor.process(KStreamBranch.java:45) at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:46) at org.apache.kafka.streams.processor.internals.StreamsMetricsImpl.measureLatencyNs(StreamsMetricsImpl.java:208) at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:124) at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:85) at org.apache.kafka.streams.kstream.internals.KStreamMap$KStreamMapProcessor.process(KStreamMap.java:42) at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:46) at org.apache.kafka.streams.processor.internals.StreamsMetricsImpl.measureLatencyNs(StreamsMetricsImpl.java:208) at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:124) at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:85) at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:80) at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:216) at org.apache.kafka.streams.processor.internals.AssignedTasks.process(AssignedTasks.java:403) at org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:317) at org.apache.kafka.streams.processor.internals.StreamThread.processAndMaybeCommit(StreamThread.java:942) at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:822) at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:774) at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:744)

[sobychacko]

@tambre These two properties should work now:

spring.cloud.stream.kafka.streams.bindings.input.consumer.keySerde: org.apache.kafka.common.serialization.Serdes$StringSerde

spring.cloud.stream.kafka.streams.bindings.output.producer.keySerde: org.apache.kafka.common.serialization.Serdes$StringSerde

When you rely on Kafka provided serdes on the inbound and outbound, you should set these two flags to true as the defaults are false for them.

spring.cloud.stream.bindings.input.consumer.useNativeDecoding: true and spring.cloud.stream.bindings.output.producer.useNativeEncoding: true

[tambre]

@sobychacko thanks for your help