Gson如何自定义Calendar序列化/反序列化
Gson如何自定义Calendar序列化/反序列化
菩提树下的杨过
发布于 2022-04-27 11:01:09
发布于 2022-04-27 11:01:09
直接开干吧，假设有这么一个类：
@Data
@AllArgsConstructor
class BeanSample {
public Calendar birthday;
@Override
public String toString() {
if (birthday == null) {
return "birthday:null";
}
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
return sdf.format(birthday.getTime());
}
}默认情况下，Gson序列化出来的结果很难看：
Gson gson = new Gson();
BeanSample bean = new BeanSample(Calendar.getInstance());
System.out.println(gson.toJson(bean));输出：
{"birthday":{"year":2022,"month":3,"dayOfMonth":20,"hourOfDay":21,"minute":18,"second":13}}以我多年的搬砖经验，加个TypeAdapter应该就可以了吧：
Gson gson = new GsonBuilder().registerTypeAdapter(Calendar.class, new TypeAdapter<Calendar>() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
@Override
public void write(JsonWriter out, Calendar value) throws IOException {
if (value == null) {
out.nullValue();
} else {
out.value(sdf.format(value.getTime()));
}
}
@Override
public Calendar read(JsonReader in) throws IOException {
//这是从json字符串反序列化的，先不管
return null;
}
}).create();
BeanSample bean = new BeanSample(Calendar.getInstance());
System.out.println(gson.toJson(bean));运行一下，居然没生效，还是刚才的格式！于是，下个断点：
发现birthday最终实例化后，类型是 GregorianCalendar（即：抽象类Calendar的子类），然后把刚才的代码略改了下：
Gson gson = new GsonBuilder().registerTypeAdapter(GregorianCalendar.class, new TypeAdapter<GregorianCalendar>() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
@Override
public void write(JsonWriter out, GregorianCalendar value) throws IOException {
if (value == null) {
out.nullValue();
} else {
out.value(sdf.format(value.getTime()));
}
}
@Override
public GregorianCalendar read(JsonReader in) throws IOException {
JsonToken token = in.peek();
switch (token) {
case NUMBER:
Date d = new Date(in.nextLong());
GregorianCalendar c = new GregorianCalendar();
c.setTime(d);
return c;
case STRING:
String s = in.nextString();
try {
Date parse = sdf.parse(s);
GregorianCalendar instance = new GregorianCalendar();
instance.setTime(parse);
return instance;
} catch (ParseException e) {
e.printStackTrace();
return null;
}
case NULL:
default:
return null;
}
}
}).create();
BeanSample bean = new BeanSample(new GregorianCalendar());
//序列化
String json = gson.toJson(bean);
System.out.println(json);
//反序列化
System.out.println(gson.fromJson(json, BeanSample.class));
System.out.println("--------");
//换成时间戳格式
json = "{\"birthday\":" + System.currentTimeMillis() + "}";
System.out.println(json);
System.out.println(gson.fromJson(json, BeanSample.class));输出：
{"birthday":"2022-04-20 22:27:08.864"}
2022-04-20 22:27:08.864
--------
{"birthday":1650464828881}
2022-04-20 22:27:08.881这样看起来好多了，而且json反序列化时，时间戳long型数字也一并做了兼容
注：gson的其它小技巧，可参考先前写的文章 去fastjson笔记
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原始发表：2022-04-20，如有侵权请联系 cloudcommunity@tencent.com 删除
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