Force Milliseconds When Serializing Instant to ISO8601 using Jackson

Question

I have some questions related to JSON serialization using Jackson in a project where I use Spring Boot 2.0.0.M6, Spring Framework 5.0.1.R

Answer 1

Solve it by using custom serializers for LocalDateTime and ZonedDateTime classes.

My solution works for me because I use only these two classes in API responses to represent date and time! I don't use Instant or Date so pay attention on it.

@Configuration
class JacksonConfig {

@Bean
fun objectMapper(): ObjectMapper {
    val mapper = ObjectMapper()
    val javaTimeModule = JavaTimeModule().apply {
        addSerializer(LocalDateTime::class.java, KeepMillisecondLocalDateTimeSerializer())
        addSerializer(ZonedDateTime::class.java, KeepMillisecondZonedDateTimeSerializer())
    }
    mapper.registerModule(javaTimeModule)
    return mapper
}

class KeepMillisecondZonedDateTimeSerializer : JsonSerializer() {
    private val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSX")

    @Throws(IOException::class)
    override fun serialize(
        value: ZonedDateTime,
        jsonGenerator: JsonGenerator,
        serializerProvider: SerializerProvider?
    ) {
        jsonGenerator.writeString(formatter.format(value))
    }
}

class KeepMillisecondLocalDateTimeSerializer : JsonSerializer() {
    private val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS")

    @Throws(IOException::class)
    override fun serialize(
        value: LocalDateTime,
        jsonGenerator: JsonGenerator,
        serializerProvider: SerializerProvider?
    ) {
        jsonGenerator.writeString(formatter.format(value))
    }
}
}