I'm using spring boot 2.3.4.RELEASE and when trying to convert a DTO containing an Instant attribute to JSON format, the jackson ObjectMapper keeps converting it to timestamp format, even with write-dates-as-timestamps option turned off.

pom.xml

```
<parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
     <version>2.3.4.RELEASE</version>
     <relativePath/> <!-- lookup parent from repository -->
</parent> 

....

<dependency>
     <groupId>com.fasterxml.jackson.datatype</groupId>
     <artifactId>jackson-datatype-jsr310</artifactId>
</dependency>

```

application.properties

```
spring.jackson.serialization.write-dates-as-timestamps = false

```

DTO:

```
@Data
public class MyDTO {

    Long id;

    @NotNull
    String number;

    @NotNull
    Integer year;

    @NotNull
    VesselContractStatusEnum status;

    Instant statusDate;
}

```

Rest Controller response:

```
{
    "id": 1,
    "number": "202000",
    "year": 2020,
    "status": "Open",
    "statusDate": 1602298800
 }

```

Following recommendations found here in StackOverflow, I tried to override the ObjectMapper using the follwoing approach, but it didn't work.

```
@Bean
@Primary
public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {

    ObjectMapper objectMapper = builder.build();

    objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);

    JavaTimeModule javaTimeModule = new JavaTimeModule();
    objectMapper.registerModule(javaTimeModule);
    objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"));

    return objectMapper;
}

```