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Convert the Date format to ISO8601
Problem
在做Rest API的輸出處理時,一定會遇到日期要顯示的格式,而日期也伴隨著timezone的問題。要顯示成甚麼樣子的格式,就看各個應用程式的需求。一開始是想仿效臉書轉為unix time,後來再為這問題爭論不休;最後我在study後,認為ISO8601比較符合我們需求,就決定為我們的顯示格式。
How to?
預設使用Jackson去做Date的轉換,會輸出為unix time。如果要達到我們的目的,可透過@JsonSerialize設定對應序列化的物件;而要接收使用者輸入轉為對應物件的話,可透過@JsonDeserialize設定對應反序列化物件。
Object with JsonSerialize and JsonDeserialize annotation
public class Event { @JsonSerialize(using=ISO8601DateSerializer.class) @JsonDeserialize(using=ISO8601DateDeserializer.class) private Date date; private String message; public Date getDate(){ return date; } public void setDate(Date date){ this.date = date; } // ... skip }
ISO8601DateSerializer for Date
public class ISO8601DateSerializer extends StdSerializer<Date> { private static final long serialVersionUID = 1L; public ISO8601DateSerializer() { super(Date.class); } @Override public void serialize(Date date, JsonGenerator json, SerializerProvider provider) throws IOException, JsonGenerationException { DateFormat df = StdDateFormat.getISO8601Format( TimeZone.getTimeZone("UTC"), Locale.getDefault()); String out = df.format(date); json.writeString(out); } }
ISO8601DateDeserializer for Date
public class ISO8601DateDeserializer extends StdDeserializer<Date> { private static final long serialVersionUID = 1L; public ISO8601DateDeserializer() { super(Date.class); } @Override public Date deserialize(JsonParser parser, DeserializationContext context) throws IOException, JsonProcessingException { try { DateFormat df = StdDateFormat.getISO8601Format( TimeZone.getTimeZone("UTC"), Locale.getDefault()); return df.parse(parser.getText()); } catch (Exception e) { return null; } } }
Reference