LocalDateTime not serializing based on given serializer registered with JavaTimeModule - spring-boot

Question

I'm facing an issue where Spring boot (v2.6.13) is not parsing LocalDateTime based on a registered serializer, the response of LocalDateTime of RestController is always an array of integers.
#Bean
public Module javaTimeModule() {
JavaTimeModule module = new JavaTimeModule();
module.addSerializer(new CustomLocalDateTimeSerializer());
return module;
}
class CustomLocalDateTimeSerializer extends StdSerializer<LocalDateTime> {
private static DateTimeFormatter formatter =
DateTimeFormatter.ofPattern("yyyy-MM-dd");
protected CustomLocalDateTimeSerializer() {
super(LocalDateTime.class);
}
#Override
public void serialize(
LocalDateTime localDateTime,
JsonGenerator jsonGenerator,
SerializerProvider serializerProvider) throws IOException {
jsonGenerator.writeString(localDateTime.format(formatter));
}
}
Notes:
Injecting object mapper and serialize the object returns the correct format.
I've defined an object mapper annotated with #Primary, but still facing the same issue.
I want to configure everything globally - don't wanna use #JsonSerialize on each attribute-
it seems like Spring is using a different object mapper for serializing a method returned object.

Answer 1

I've found the issue and resolved it.
I have a WebMvcConfigurationSupport configuration which was overriding the configured object mapper.
I've solved it using following code
private final ObjectMapper objectMapper;
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters)
{
var converter = new MappingJackson2HttpMessageConverter();
converter.setObjectMapper(objectMapper);
converters.add(converter);
super.configureMessageConverters(converters);
}