Jackson SerializationFeature.WRITE_DATES_AS_TIMESTAMPS not turning off timestamps in spring

After lots of messing around I found that the following code fixed the problem:

public class MVCConfig extends WebMvcConfigurerAdapter {
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) { 
        for (HttpMessageConverter<?> converter : converters) {
            if (converter instanceof MappingJackson2HttpMessageConverter) {
                MappingJackson2HttpMessageConverter jsonMessageConverter = (MappingJackson2HttpMessageConverter) converter;
                ObjectMapper objectMapper = jsonMessageConverter.getObjectMapper();
                objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
                break;
            }
        }
    }
}

I'm not sure if there is an easier way to access the Jackson MVC message converter and configure it. But this is working for me.

Yes I agree with @Feyyaz: adding config to the properties/yml file is the way to config the default, contextual (de)serializer, when this is out of your control and only left to be manipulated by Spring context.

See this part of Spring documentation for more details:

https://docs.spring.io/spring-boot/docs/current/reference/html/howto-spring-mvc.html#howto-customize-the-jackson-objectmapper

Citation in case of original link removal:

79.3 Customize the Jackson ObjectMapper

Spring MVC (client and server side) uses HttpMessageConverters to negotiate content conversion in an HTTP exchange. If Jackson is on the classpath, you already get the default converter(s) provided by Jackson2ObjectMapperBuilder, an instance of which is auto-configured for you. The ObjectMapper (or XmlMapper for Jackson XML converter) instance (created by default) has the following customized properties:

• MapperFeature.DEFAULT_VIEW_INCLUSION is disabled
• DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES is disabled
• SerializationFeature.WRITE_DATES_AS_TIMESTAMPS is disabled

Spring Boot also has some features to make it easier to customize this behavior. You can configure the ObjectMapper and XmlMapper instances by using the environment. Jackson provides an extensive suite of simple on/off features that can be used to configure various aspects of its processing. These features are described in six enums:

| Enum | Property | Values | | - | - | - | |com.fasterxml.jackson.databind.DeserializationFeature|spring.jackson.deserialization.<feature_name>|true, false| |com.fasterxml.jackson.core.JsonGenerator.Feature|spring.jackson.generator.<feature_name>|true, false| |com.fasterxml.jackson.databind.MapperFeature|spring.jackson.mapper.<feature_name>|true, false| |com.fasterxml.jackson.core.JsonParser.Feature|spring.jackson.parser.<feature_name>|true, false| |com.fasterxml.jackson.databind.SerializationFeature|spring.jackson.serialization.<feature_name>|true, false| |com.fasterxml.jackson.annotation.JsonInclude.Include|spring.jackson.default-property-inclusion|always, non_null, non_absent, non_default, non_empty|

For example, to enable pretty print, set spring.jackson.serialization.indent_output=true. Note that, thanks to the use of relaxed binding, the case of indent_output does not have to match the case of the corresponding enum constant, which is INDENT_OUTPUT. This environment-based configuration is applied to the auto-configured Jackson2ObjectMapperBuilder bean and applies to any mappers created by using the builder, including the auto-configured ObjectMapper bean. The context’s Jackson2ObjectMapperBuilder can be customized by one or more Jackson2ObjectMapperBuilderCustomizer beans. Such customizer beans can be ordered (Boot’s own customizer has an order of 0), letting additional customization be applied both before and after Boot’s customization. Any beans of type com.fasterxml.jackson.databind.Module are automatically registered with the auto-configured Jackson2ObjectMapperBuilder and are applied to any ObjectMapper instances that it creates. This provides a global mechanism for contributing custom modules when you add new features to your application. If you want to replace the default ObjectMapper completely, either define a @Bean of that type and mark it as @Primary or, if you prefer the builder-based approach, define a Jackson2ObjectMapperBuilder @Bean. Note that, in either case, doing so disables all auto-configuration of the ObjectMapper. If you provide any @Beans of type MappingJackson2HttpMessageConverter, they replace the default value in the MVC configuration. Also, a convenience bean of type HttpMessageConverters is provided (and is always available if you use the default MVC configuration). It has some useful methods to access the default and user-enhanced message converters. See the “Section 79.4, “Customize the @ResponseBody Rendering”” section and the WebMvcAutoConfiguration source code for more details.

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Examples:

spring:
  jackson:
    default-property-inclusion: non_null # to exclude null in json serialization
    serialization:
      write-dates-as-timestamps: true # write milliseconds since epoch in the final json

Or:

spring.jackson.default-property-inclusion: non_null # to exclude null in json serialization
spring.jackson.serialization.write-dates-as-timestamps: true # write milliseconds since epoch in the final json