Come On,一起使用java8全新的日期和时间API
发布时间: 2020-06-18 13:46:25文章作者: 网站编辑阅读量: 345
Come On,一起使用java8全新的日期和时间API
LocalDate
只会获取年月日
创建LocalDate
//获取当前年月日
LocalDate localDate = LocalDate.now();
//构造指定的年月日
LocalDate localDate1 = LocalDate.of(2019, 9, 10);
获取年、月、日、星期几
int year = localDate.getYear();
int year1 = localDate.get(ChronoField.YEAR);
Month month = localDate.getMonth();
int month1 = localDate.get(ChronoField.MONTH_OF_YEAR);
int day = localDate.getDayOfMonth();
int day1 = localDate.get(ChronoField.DAY_OF_MONTH);
DayOfWeek dayOfWeek = localDate.getDayOfWeek();
int dayOfWeek1 = localDate.get(ChronoField.DAY_OF_WEEK);
LocalTime
只会获取几点几分几秒
创建LocalTime
LocalTime localTime = LocalTime.of(13, 51, 10);
LocalTime localTime1 = LocalTime.now();
获取时分秒
//获取小时
int hour = localTime.getHour();
int hour1 = localTime.get(ChronoField.HOUR_OF_DAY);
//获取分
int minute = localTime.getMinute();
int minute1 = localTime.get(ChronoField.MINUTE_OF_HOUR);
//获取秒
int second = localTime.getSecond();
int second1 = localTime.get(ChronoField.SECOND_OF_MINUTE);
LocalDateTime
获取年月日时分秒,等于LocalDate+LocalTime
创建LocalDateTime
LocalDateTime localDateTime = LocalDateTime.now();
LocalDateTime localDateTime1 = LocalDateTime.of(2019, Month.SEPTEMBER, 10, 14, 46, 56);
LocalDateTime localDateTime2 = LocalDateTime.of(localDate, localTime);
LocalDateTime localDateTime3 = localDate.atTime(localTime);
LocalDateTime localDateTime4 = localTime.atDate(localDate);
获取LocalDate
LocalDate localDate2 = localDateTime.toLocalDate();
获取LocalTime
LocalTime localTime2 = localDateTime.toLocalTime();
**Instant**
获取秒数
- 创建Instant对象
Instant instant = Instant.now();
- 获取秒数
long currentSecond = instant.getEpochSecond();
- 获取毫秒数
long currentMilli = instant.toEpochMilli();
个人觉得如果只是为了获取秒数或者毫秒数,使用System.currentTimeMillis()来得更为方便
修改LocalDate、LocalTime、LocalDateTime、Instant
LocalDate、LocalTime、LocalDateTime、Instant为不可变对象,修改这些对象对象会返回一个副本
- 增加、减少年数、月数、天数等 以LocalDateTime为例
LocalDateTime localDateTime = LocalDateTime.of(2019, Month.SEPTEMBER, 10,
14, 46, 56);
//增加一年
localDateTime = localDateTime.plusYears(1);
localDateTime = localDateTime.plus(1, ChronoUnit.YEARS);
//减少一个月
localDateTime = localDateTime.minusMonths(1);
localDateTime = localDateTime.minus(1, ChronoUnit.MONTHS);
- 通过with修改某些值
//修改年为2019
localDateTime = localDateTime.withYear(2020);
//修改为2022
localDateTime = localDateTime.with(ChronoField.YEAR, 2022);
还可以修改月、日 时间计算
比如有些时候想知道这个月的最后一天是几号、下个周末是几号,通过提供的时间和日期API可以很快得到答案
LocalDate localDate = LocalDate.now();
LocalDate localDate1 = localDate.with(firstDayOfYear());
比如通过firstDayOfYear()返回了当前日期的第一天日期,还有很多方法这里不在举例说明
**格式化时间**
LocalDate localDate = LocalDate.of(2019, 9, 10);
String s1 = localDate.format(DateTimeFormatter.BASIC_ISO_DATE);
String s2 = localDate.format(DateTimeFormatter.ISO_LOCAL_DATE);
//自定义格式化
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("dd/MM/yyyy");
String s3 = localDate.format(dateTimeFormatter);
DateTimeFormatter默认提供了多种格式化方式,如果默认提供的不能满足要求,可以通过DateTimeFormatter的ofPattern方法创建自定义格式化方式
**解析时间**
LocalDate localDate1 = LocalDate.parse("20190910", DateTimeFormatter.BASIC_ISO_DATE);
LocalDate localDate2 = LocalDate.parse("2019-09-10", DateTimeFormatter.ISO_LOCAL_DATE);
和SimpleDateFormat相比,DateTimeFormatter是线程安全的
**小结**
LocalDateTime:Date有的我都有,Date没有的我也有,日期选择请Pick Me。
SpringBoot中应用LocalDateTime
1.将LocalDateTime字段以时间戳的方式返回给前端
添加日期转化类
public class LocalDateTimeConverter extends JsonSerializer {
@Override
public void serialize(LocalDateTime value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
gen.writeNumber(value.toInstant(ZoneOffset.of("+8")).toEpochMilli());
}
}
并在LocalDateTime字段上添加@JsonSerialize(using = LocalDateTimeConverter.class)注解,如下:
@JsonSerialize(using = LocalDateTimeConverter.class)
protected LocalDateTime gmtModified;
2.将LocalDateTime字段以指定格式化日期的方式返回给前端
在LocalDateTime字段上添加@JsonFormat(shape=JsonFormat.Shape.STRING, pattern="yyyy-MM-dd HH:mm:ss")注解即可,如下:
@JsonFormat(shape=JsonFormat.Shape.STRING, pattern="yyyy-MM-dd HH:mm:ss")
protected LocalDateTime gmtModified;
3.对前端传入的日期进行格式化
在LocalDateTime字段上添加@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")注解即可,如下:
@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
protected LocalDateTime gmtModified