Java 8 LocalDate Jackson format

java

date-formatting

jackson-serialization

localdate

byAnton Shumikhin·Oct 22, 2024

To format LocalDate fields using Jackson, leverage the @JsonFormat annotation with the desired pattern. Remember to register the JavaTimeModule to handle Java 8 dates efficiently.

@JsonFormat(pattern = "yyyy-MM-dd") // Remember this pattern! It's kinda like a secret passcode.
private LocalDate date;

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JavaTimeModule()); // plug-in for our 3D Java 8 date-time printer
objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS); // No digits, no problem. We don't need 'em.

Get rid of timezone troubles

Timezones can be quiet little troublemakers. Jackson operates in UTC by default. Let your DateTimeFormatter save you from the twilight zone.

@JsonFormat(pattern = "yyyy-MM-dd", timezone = "UTC") // We're on universal time. VERY universal.
private LocalDate date;

Custom formats: breaking the mould

If ISO is too mainstream for you, custom serializer and deserializer can make your day:

// Custom serializer
public class CustomLocalDateSerializer extends StdSerializer<LocalDate> {
    private static final DateTimeFormatter MY_FANCY_FORMATTER = DateTimeFormatter.ofPattern("dd-MM-yyyy");

    public CustomLocalDateSerializer() {
        super(LocalDate.class);
    }

    @Override
    public void serialize(LocalDate value, JsonGenerator gen, SerializerProvider sp) throws IOException {
        gen.writeString(value.format(MY_FANCY_FORMATTER)); // See how fancy that is? Top-hat level fancy.
    }
}

// Custom deserializer
public class CustomLocalDateDeserializer extends StdDeserializer<LocalDate> {
    private static final DateTimeFormatter MY_FANCY_FORMATTER = DateTimeFormatter.ofPattern("dd-MM-yyyy");

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

    @Override
    public LocalDate deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        return LocalDate.parse(p.getText(), MY_FANCY_FORMATTER); // This JSON is so fancy, it's monocled.
    }
}

@JsonSerialize(using = CustomLocalDateSerializer.class)
@JsonDeserialize(using = CustomLocalDateDeserializer.class)
private LocalDate date;

Unravel common issues

Facing issues? Just like in a mystery novel, check if all characters (dependencies) are trustworthy:

Is your version of jackson-databind getting along with jackson-datatype-jsr310?
If we're in Spring Boot town, the built-in dependency management might be your Sherlock.

And if things get 'elementary' (read: hard), enabling TRACE logging for com.fasterxml.jackson or even trying out JAXB annotations might yield some clues.

Under the hood: more on configurations

Be prepared to handle occasional plot-twists. Challenges can arise through:

Serialization of nulls: Jackson can serialize them as null or "", or even skip null fields - all depending on your configuration.
Arrays and Collections: Make sure JavaTimeModule is handy while serializing LocalDate within List or Array.
Different Locales: Expedition in different locales can give different results. Be ready with necessary configurations and travel guides (formatters).

Making peace with older systems

When dealing with older systems, consider:

Legacy Date Support: Configure Jackson to smoothly translate between LocalDate and older Date.
Non-standard Patterns: Have an unconventional date pattern? Use DateTimeFormatter inline with @JsonFormat.
Mixing Date Types: If your JSON is a cocktail of date types (LocalDate, LocalDateTime, etc.), ensure each has its format or drinks responsibly (custom serializer/deserializer).