[SpringBoot] Jackson 사용시 Could not write JSON: No serializer found for class.. 오류 발생 해결법

들어가며

• Class를 Serialize 하는 과정에서 아래와 같은 에러가 발생하였다. 

Exception in thread "Thread-5" org.springframework.messaging.converter.MessageConversionException: Could not write JSON: No serializer found for class com.tact.io.domain.socket.WaitMessage and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.tact.io.domain.socket.SocketMessage["body"]); nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class com.tact.io.domain.socket.WaitMessage and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.tact.io.domain.socket.SocketMessage["body"])
	at org.springframework.messaging.converter.MappingJackson2MessageConverter.convertToInternal(MappingJackson2MessageConverter.java:284)
	at org.springframework.messaging.converter.AbstractMessageConverter.toMessage(AbstractMessageConverter.java:201)
	at org.springframework.messaging.converter.CompositeMessageConverter.toMessage(CompositeMessageConverter.java:96)
	at org.springframework.messaging.core.AbstractMessageSendingTemplate.doConvert(AbstractMessageSendingTemplate.java:181)
	at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:150)
	at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:129)
	at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:122)
	at com.tact.io.service.GamePool.sendMessage(GamePool.java:189)
	at com.tact.io.service.GamePool.run(GamePool.java:49)
	at java.lang.Thread.run(Thread.java:748)
Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class com.tact.io.domain.socket.WaitMessage and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.tact.io.domain.socket.SocketMessage["body"])
	at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77)
	at com.fasterxml.jackson.databind.SerializerProvider.reportBadDefinition(SerializerProvider.java:1191)
	at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:313)
	at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:71)
	at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:33)
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480)
Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class com.tact.io.domain.socket.WaitMessage and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.tact.io.domain.socket.SocketMessage["body"])

	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
	at com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:2655)
	at org.springframework.messaging.converter.MappingJackson2MessageConverter.convertToInternal(MappingJackson2MessageConverter.java:268)
	... 9 more

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해결 방법

• 문제의 원인은 필드가 없는 클래스를 Serialize하려고 하기 때문이었다. 
• 해결 방법은 두가지가 있다.

어노테이션 추가

• 해당 클래스에 아래의 어노테이션을 추가해준다.

@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})

application.properties 수정

• application.properties 파일에 아래 설정을 추가해준다.

spring.jackson.serialization.FAIL_ON_EMPTY_BEANS=false

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관련글

[SpringBoot] Application 실행시 다양한 시점의 Event Listener 등록하는 방법

[SpringBoot] properties 파일 정의된 프로퍼티 클래스로 묶어서 사용하는 방법 (@ConfigurationProperties 사용)

[Spring Boot] ApplicationArguments 사용법

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끝으로

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