Missing required configuration "value.serializer" which has no default value.

[nyeastll]

The spring-boot-kafka example generate this error message, here it is the stack.

org.apache.kafka.common.config.ConfigException: Missing required configuration "value.serializer" which has no default value.
at org.apache.kafka.common.config.ConfigDef.parseValue(ConfigDef.java:477) ~[kafka-clients-2.5.0.jar:na]
at org.apache.kafka.common.config.ConfigDef.parse(ConfigDef.java:467) ~[kafka-clients-2.5.0.jar:na]
at org.apache.kafka.common.config.AbstractConfig.(AbstractConfig.java:108) ~[kafka-clients-2.5.0.jar:na]
at org.apache.kafka.common.config.AbstractConfig.(AbstractConfig.java:129) ~[kafka-clients-2.5.0.jar:na]
at org.apache.kafka.clients.producer.ProducerConfig.(ProducerConfig.java:481) ~[kafka-clients-2.5.0.jar:na]
at org.apache.kafka.clients.producer.KafkaProducer.(KafkaProducer.java:326) ~[kafka-clients-2.5.0.jar:na]
at org.apache.kafka.clients.producer.KafkaProducer.(KafkaProducer.java:287) ~[kafka-clients-2.5.0.jar:na]
at org.springframework.kafka.core.DefaultKafkaProducerFactory.createRawProducer(DefaultKafkaProducerFactory.java:645) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.kafka.core.DefaultKafkaProducerFactory.createKafkaProducer(DefaultKafkaProducerFactory.java:520) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.kafka.core.DefaultKafkaProducerFactory.doCreateProducer(DefaultKafkaProducerFactory.java:497) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.kafka.core.DefaultKafkaProducerFactory.createProducer(DefaultKafkaProducerFactory.java:458) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.kafka.core.DefaultKafkaProducerFactory.createProducer(DefaultKafkaProducerFactory.java:452) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.kafka.core.KafkaTemplate.getTheProducer(KafkaTemplate.java:662) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.kafka.core.KafkaTemplate.doSend(KafkaTemplate.java:548) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.kafka.core.KafkaTemplate.send(KafkaTemplate.java:360) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at io.reflectoring.kafka.KafkaSenderExample.sendMessage(KafkaSenderExample.java:34) ~[classes/:na]
at io.reflectoring.kafka.InitSend.initiateSendingMessage(InitSend.java:36) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.context.event.ApplicationListenerMethodAdapter.doInvoke(ApplicationListenerMethodAdapter.java:305) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.context.event.ApplicationListenerMethodAdapter.processEvent(ApplicationListenerMethodAdapter.java:190) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.context.event.ApplicationListenerMethodAdapter.onApplicationEvent(ApplicationListenerMethodAdapter.java:153) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:404) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:361) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.boot.context.event.EventPublishingRunListener.running(EventPublishingRunListener.java:108) ~[spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplicationRunListeners.running(SpringApplicationRunListeners.java:77) ~[spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:330) ~[spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) ~[spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at io.reflectoring.kafka.SpringKafkaExampleApplication.main(SpringKafkaExampleApplication.java:12) ~[classes/:na]

2020-12-16 20:46:06.414 INFO 25592 --- [ 1-0-C-1] o.s.k.l.KafkaMessageListenerContainer : reflectoring-user-mc: partitions revoked: [reflectoring-user-0]

Any idea of why this will occur? thanks.

[sgrmgj]

yes the producer config requires a default value serializer as well - so essentially this should be -
@bean
public Map<String, Object> producerConfigs() {
Map<String, Object> props = new HashMap<>();
props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
return props;
}