temp.java

@Configuration
@EnableWebMvc
public class MvcConfig implements WebMvcConfigurer {

  ...

  @Override
  public void extendMessageConverters(final List<HttpMessageConverter<?>> converters) {
    DateTimeFormatter formatter = DataTimeFormatter.ofPattern("yyyyMMddHHmmss");

    ObjectMapper objectMapper = Jackson2ObjectMapperBuilder
        .json()
        .featureToEnable(SerializationFeature.INDENT_OUTPUT)
        .deserializerByType(LocalDateTime.class, new LocalDateTimeDeserializer(formatter))
        .simpleDateFormat("yyyyMMddHHmmss")
        .build();
    converters.add(0, new MappingJackson2HttpMessageConverter(objectMapper));
  }

}