Gson转Json字符串时将日期类型转换成Long型的方法

public class DateSerializer implements JsonSerializer<Date> {    
    public JsonElement serialize(Date src, Type typeOfSrc, JsonSerializationContext context) {              
        return new JsonPrimitive(src.getTime());    
    }
}

public class DateDeserializer implements JsonDeserializer<Date> {    
    public Date deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {        
        return new java.util.Date(json.getAsJsonPrimitive().getAsLong());    
    }
}

public class GsonUtils {
    private static Gson instance = null;
    public synchronized static Gson getGson(){
        if(instance == null) {
            GsonBuilder builder = new GsonBuilder();
            builder.addSerializationExclusionStrategy(new IgnoreStrategy());
            builder.registerTypeAdapter(java.util.Date.class, new DateSerializer()).setDateFormat(DateFormat.LONG);
            builder.registerTypeAdapter(java.util.Date.class, new DateDeserializer()).setDateFormat(DateFormat.LONG);
            instance = builder.create();
        }
        return instance;
    }
}