Jackson JSON 序列化：時區與日期處理

@Configuration
public class JsonConfig {

@Bean
public ObjectMapper objectMapper() {
ObjectMapper mapper = new ObjectMapper();

// 1. 允許序列化私有欄位
mapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);

// 2. 日期格式設定
mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
mapper.setDateFormat(new SimpleDateFormat(“yyyy-MM-dd’T’HH:mm:ss.SSS’Z’”));

// 3. 設定 UTC 時區
mapper.setTimeZone(TimeZone.getTimeZone(“UTC”));

// 4. 支援 Java 8 時間 API
mapper.registerModule(new JavaTimeModule());

// 5. 自定義序列化器
SimpleModule module = new SimpleModule();
module.addSerializer(ZonedDateTime.class, new ZonedDateTimeSerializer());
mapper.registerModule(module);

// 6. 忽略未知欄位（平台加新欄位不會報錯）
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

return mapper;
}
}

public class ZonedDateTimeSerializer extends JsonSerializer<ZonedDateTime> {

private static final DateTimeFormatter FORMATTER =
DateTimeFormatter.ofPattern(“yyyy-MM-dd’T’HH:mm:ss.SSS’Z’”);

@Override
public void serialize(
ZonedDateTime value,
JsonGenerator gen,
SerializerProvider provider) throws IOException {

// 無論輸入什麼時區，都轉成 UTC 輸出
ZonedDateTime utc = value.withZoneSameInstant(ZoneId.of(“UTC”));
gen.writeString(FORMATTER.format(utc));
}
}

// 輸入：台灣時間
ZonedDateTime taiwanTime = ZonedDateTime.now(ZoneId.of(“Asia/Taipei”));
// 2024-03-18T15:30:00+08:00[Asia/Taipei]

// 輸出：自動轉成 UTC
String json = objectMapper.writeValueAsString(Map.of(“time”, taiwanTime));
// {“time”:”2024-03-18T07:30:00.000Z”}

@Component
public class JsonUtil {

private static ObjectMapper mapper;

@Autowired
public void setMapper(ObjectMapper mapper) {
JsonUtil.mapper = mapper;
}

/**
* 物件轉 JSON
*/
public static String toJson(Object obj) {
try {
return mapper.writeValueAsString(obj);
} catch (JsonProcessingException e) {
throw new JsonException(“序列化失敗”, e);
}
}

/**
* JSON 轉物件
*/
public static <T> T fromJson(String json, Class<T> clazz) {
try {
return mapper.readValue(json, clazz);
} catch (JsonProcessingException e) {
throw new JsonException(“反序列化失敗”, e);
}
}

/**
* JSON 轉泛型物件
*/
public static <T> T fromJson(String json, TypeReference<T> type) {
try {
return mapper.readValue(json, type);
} catch (JsonProcessingException e) {
throw new JsonException(“反序列化失敗”, e);
}
}

/**
* JSON 轉 List
*/
public static <T> List<T> fromJsonList(String json, Class<T> clazz) {
try {
JavaType type = mapper.getTypeFactory()
.constructCollectionType(List.class, clazz);
return mapper.readValue(json, type);
} catch (JsonProcessingException e) {
throw new JsonException(“反序列化失敗”, e);
}
}

/**
* JSON 轉 Map
*/
public static Map<String, Object> toMap(String json) {
return fromJson(json, new TypeReference<>() {});
}
}

public class DateConverter {

/**
* Unix timestamp → ZonedDateTime（蝦皮）
*/
public static ZonedDateTime fromUnixTimestamp(long timestamp) {
return Instant.ofEpochSecond(timestamp)
.atZone(ZoneId.of(“UTC”));
}

/**
* ISO 8601 → ZonedDateTime（Yahoo）
*/
public static ZonedDateTime fromISO(String isoString) {
return ZonedDateTime.parse(isoString);
}

/**
* 台灣時間字串 → ZonedDateTime（Momo）
*/
public static ZonedDateTime fromTaiwanTime(String timeStr) {
DateTimeFormatter formatter =
DateTimeFormatter.ofPattern(“yyyy/MM/dd HH:mm:ss”);

LocalDateTime ldt = LocalDateTime.parse(timeStr, formatter);
return ldt.atZone(ZoneId.of(“Asia/Taipei”));
}

/**
* 轉成台灣時間顯示
*/
public static String toTaiwanDisplay(ZonedDateTime time) {
ZonedDateTime taiwanTime = time.withZoneSameInstant(
ZoneId.of(“Asia/Taipei”)
);
return taiwanTime.format(
DateTimeFormatter.ofPattern(“yyyy/MM/dd HH:mm:ss”)
);
}
}

// 從蝦皮 API 取得資料
long shopeeTimestamp = 1710748800;
ZonedDateTime orderTime = DateConverter.fromUnixTimestamp(shopeeTimestamp);

// 存入資料庫（UTC）
order.setCreatedAt(orderTime);
orderRepository.save(order);

// 回傳 API（自動轉成 UTC JSON）
return JsonUtil.toJson(order);
// {“createdAt”:”2024-03-18T08:00:00.000Z”}

// 前端顯示（轉成台灣時間）
String display = DateConverter.toTaiwanDisplay(order.getCreatedAt());
// 2024/03/18 16:00:00