Jackson , java.time , ISO 8601 , serialize without milliseconds

Update:

Just add a @JsonFormat annotation with the date format above the Instant property. It's very easy.

In the case you have an ObjectMapper with the JavaTimeModule like next:

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());

If you have a class with an Instant property, you should add the @JsonFormat annotation and put the date pattern which hasn't milliseconds. It would be like next:

public static class TestDate {

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd hh:mm:ss", timezone = "UTC")
    Instant instant;

    //getters & setters
}

So if you serialize an object to Json it works perfectly:

String json = mapper.writeValueAsString(testDate);
System.out.println(json); 

Output

{"instant":"2016-11-10 06:03:06"}

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Old Answer. I don't know why but It doesn't work properly:

You could use the Jackson2ObjectMapperBuilder to build it.

You just need to add the dateFormat you want. It would be something like next:

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

ObjectMapper mapper = Jackson2ObjectMapperBuilder
            .json()       
            .featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS) 
            .modules(new JavaTimeModule())
            .dateFormat(dateFormat)
            .build();

Here is an alternative which is something you can set globally, but will need you to use ZonedDateTime with instant formatter as we can't set the format for the Instant Serializer provided with Java Time Module.

You wont see any side effects of using zoned date time for instant as jackson serializes the zone id separately and is disabled by default. So technically, this is similar to applying the formatter to Instant.

When used this way, the ZonedDateTime serializer delegates the serialization to InstantBaseSerializer and uses the specified custom format.

@RunWith(JUnit4.class)
public class InstantNoMillisTest {

    private ObjectMapper objectMapper;

    @Before
    public void init() {
        JavaTimeModule module = new JavaTimeModule();
        ZonedDateTimeSerializer zonedDateTimeSerializer = new ZonedDateTimeSerializer(new DateTimeFormatterBuilder().appendInstant(0).toFormatter());
        module.addSerializer(ZonedDateTime.class, zonedDateTimeSerializer);
        module.addDeserializer(ZonedDateTime.class, InstantDeserializer.ZONED_DATE_TIME);

        objectMapper = Jackson2ObjectMapperBuilder.json()
                .modules(module)
                .featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
                .build();
    }

    @Test
    public void serialize() throws IOException {
        ZonedDateTime zonedDateTime = ZonedDateTime.now();
        String noMillis = objectMapper.writeValueAsString(zonedDateTime);
        System.out.print(noMillis);
    }

    @Test
    public void deserialize() throws IOException {
        String dateTime = "\"2017-10-26T12:54:59Z\"";
        ZonedDateTime noMillis = objectMapper.readValue(dateTime, ZonedDateTime.class);
        System.out.print(noMillis);
    }
}