Custom `LocalDate` deserializer not being used with 2.11, jsr-310 datatype module

Dear Jackson team,

It seems that as of Jackson 2.11 my custom (date) deserializer is no longer being used by the object mapper. I’ve tried various ways of registering the deserializer but none seem to work. In the previous version (2.10.4) this was not a problem.

Strangely the JSR310 LocalDateDeserializer is being detected and registered automatically from the classpath, skipping the deserializer in my custom module.

Example:

public class CustomLocalDateDeserializerTest {

    @Test
    public void parse_dates_shouldSucceed() throws JsonProcessingException {
        SimpleModule module = new SimpleModule();
        module.addDeserializer(LocalDate.class, new CustomLocalDateDeserializer());

        ObjectMapper objectMapper = JsonMapper.builder()
            .addModule(module)
            .build();

        final String json = "{\"endDate\":1567202400000,\"startDate\":1564610400000}";

        Dates dates = objectMapper.readValue(json, Dates.class);
        assertNotNull(dates);
        assertEquals(LocalDate.of(2019, 8, 1), dates.getStartDate());
        assertEquals(LocalDate.of(2019, 8, 31), dates.getEndDate());
    }

    @Getter
    @Setter
    public static class Dates {

        private LocalDate startDate;
        private LocalDate endDate;

    }

}

@Slf4j
public final class CustomLocalDateDeserializer extends com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer {

    public CustomLocalDateDeserializer() {
        super(DateTimeFormatter.ISO_LOCAL_DATE);
    }

    @Override
    public LocalDate deserialize(JsonParser parser, DeserializationContext context) throws IOException {
        if (parser.hasToken(JsonToken.VALUE_NUMBER_INT)) {
            long value = parser.getLongValue();
            if (!isValidEpochDay(value)) {
                return toLocalDate(value);
            }
        }
        return super.deserialize(parser, context);
    }

    private static boolean isValidEpochDay(long value) {
        try {
            ChronoField.EPOCH_DAY.checkValidValue(value);
        } catch (DateTimeException ex) {
            log.trace("Date value {} is not a valid epoch day value.", value);
            return false;
        }
        return true;
    }

    private static LocalDate toLocalDate(Long millis) {
        Instant instant = Instant.ofEpochMilli(millis);
        LocalDateTime ldt = LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
        return LocalDate.of(ldt.getYear(), ldt.getMonth(), ldt.getDayOfMonth());
    }

}

[jeroenvs]

Pardon, I’ve found the probleem and it’s indeed not a bug. Between 2.10.4 en 2.11.0 the deserializer now uses the following method:

    @Override
    protected LocalDateDeserializer withShape(JsonFormat.Shape shape) { return new LocalDateDeserializer(this, shape); }

Which creates a new deserializer, replacing my custom deserializer. I’ve solved the problem by using composition over inheritance:

public final class CustomLocalDateDeserializer extends StdDeserializer<LocalDate> {

    protected CustomLocalDateDeserializer() {
        super(LocalDate.class);
    }

    @Override
    public LocalDate deserialize(JsonParser parser, DeserializationContext context) throws IOException {
        if (parser.hasToken(JsonToken.VALUE_NUMBER_INT)) {
            long value = parser.getLongValue();
            if (!isValidEpochDay(value)) {
                return toLocalDate(value);
            }
        }

        return LocalDateDeserializer.INSTANCE.deserialize(parser, context);
    }

    private static boolean isValidEpochDay(long value) {
        try {
            ChronoField.EPOCH_DAY.checkValidValue(value);
        } catch (DateTimeException ex) {
            return false;
        }
        return true;
    }

    private static LocalDate toLocalDate(Long millis) {
        Instant instant = Instant.ofEpochMilli(millis);
        LocalDateTime ldt = LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
        return LocalDate.of(ldt.getYear(), ldt.getMonth(), ldt.getDayOfMonth());
    }

}

[cowtowncoder]

Ok, glad you figure out the issue. Sub-classing is quite fragile, unfortunately, and composition is encouraged, for this reason.