Java8中的LocalDateTime使用

Java8中的LocalDateTime使用

一、基本操作

LocalDateTime、LocalDate、LocalTime、Date、Timestamp、String 互转，及其LocalDateTime 相关计算

@Test
public void testLocalDateTime() {

	///////////////////////////// 转换 ///////////////////////////

	// now()
	LocalDateTime localDateTime = LocalDateTime.now();
	System.out.println("now -> " + localDateTime);

	// LocalDateTime -> LocalDate
	LocalDate localDate = localDateTime.toLocalDate();
	System.out.println("LocalDate -> " + localDate);

	// LocalDateTime -> LocalTime
	LocalTime localTime = localDateTime.toLocalTime();
	System.out.println("localTime -> " + localTime);

	// LocalDateTime -> LocalDateTime
	LocalDateTime time = LocalDateTime.of(localDateTime.toLocalDate(), localDateTime.toLocalTime());
	System.out.println("LocalDateTime -> LocalDateTime = " + time);

	// LocalDateTime -> Timestamp
//        long timestamp = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli();
//        long timestamp = LocalDateTime.now().atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
	Timestamp timestamp1 = Timestamp.valueOf(localDateTime);
	long timestamp = timestamp1.getTime();
	Timestamp timestamp2 = Timestamp.from(Instant.ofEpochMilli(timestamp));
	System.out.println("timestamp1 = " + timestamp1);
	System.out.println("timestamp2 = " + timestamp2);
	System.out.println("LocalDateTime -> Timestamp = " + timestamp);

	// Timestamp -> LocalDateTime
	Instant instant = Instant.ofEpochMilli(timestamp);
	LocalDateTime timestampToLocalDateTime = LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
	System.out.println("Timestamp -> LocalDateTime = " + timestampToLocalDateTime);

	// LocalDateTime -> String
	DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
	String format = time.format(dateTimeFormatter);
	System.out.println("LocalDateTime -> String = " + format);

	// Date -> LocalDateTime
	Date now = new Date();
//        LocalDateTime dateToLocalDateTime = now.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
	LocalDateTime dateToLocalDateTime = Instant.ofEpochMilli(now.getTime()).atZone(ZoneId.systemDefault()).toLocalDateTime();
	System.out.println("LocalDateTime -> Date = " + dateToLocalDateTime);

	// LocalDateTime -> Date
	Date date = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
	System.out.println("Date -> LocalDateTime = " + date);


	///////////////////////////// 计算 ///////////////////////////

	// LocalDate plus Time
	LocalDate localDate1 = localDate.plusDays(1);
	LocalDate localDate2 = localDate.plus(1, ChronoUnit.DAYS);
	System.out.println("LocalDate plus Time = " + localDate1);

	// LocalTime plus Time
	LocalTime localTime1 = localTime.plusHours(1);
	LocalTime localTime2 = localTime.plus(1, ChronoUnit.HOURS);
	System.out.println("LocalTime plus Time = " + localTime2);

	// first/last day of Time
	LocalDate withDayOfMonth = localDate.withDayOfMonth(1);
	LocalDate firstDayOfMonth = localDate.with(TemporalAdjusters.firstDayOfMonth());
	LocalDate lastDayOfMonth = localDate.with(TemporalAdjusters.lastDayOfMonth());
//        LocalDateTime firstDayOfMonth2 = localDateTime.with(TemporalAdjusters.firstDayOfMonth()).toLocalDate().atStartOfDay();
	LocalDateTime firstDayOfMonth2 = localDateTime.with(TemporalAdjusters.firstDayOfMonth()).with(LocalTime.MIN);
	LocalDateTime lastDayOfMonth2 = localDateTime.with(TemporalAdjusters.lastDayOfMonth()).with(LocalTime.MAX);
	System.out.println("firstDayOfMonth = " + firstDayOfMonth2);
	System.out.println("lastDayOfMonth = " + lastDayOfMonth2);

	// compate
	LocalDateTime compateTime = LocalDateTime.of(2020, 05, 02, 12, 13, 14);
	boolean isAfter = localDateTime.isAfter(compateTime);
	System.out.println(localDateTime + " isAfter " + compateTime + " = " + isAfter);
	boolean isBefore = localDateTime.isBefore(compateTime);
	System.out.println(localDateTime + " isBefore " + compateTime + " = " + isBefore);
	long between = Math.abs(ChronoUnit.DAYS.between(compateTime, localDateTime));
	System.out.println(localDateTime + " between " + compateTime + " = " + between);
}

二、SpringBoot 转换相关配置

全局配置

【配置】

#--------- JSON 时区设置 ---------#
spring.jackson.date-format=yyyy-MM-dd HH:mm:ss
spring.jackson.time-zone=GMT+8

【代码】

import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

/**
 * 解决 LocalDateTime 格式化日期问题(日期带T)
 * 2018-10-09T17:39:07.097
 */
@Configuration
public class LocalDateTimeSerializerConfig {

    @Value("${spring.jackson.date-format:yyyy-MM-dd HH:mm:ss}")
    private String pattern;

    @Bean
    public LocalDateTimeSerializer localDateTimeDeserializer() {
        return new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(pattern));
    }

    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() {
        return builder -> builder.serializerByType(LocalDateTime.class, localDateTimeDeserializer());
    }

}

实体类局部配置

 /*
  * 创建时间
  * @JsonFormat  序列化（bean转json）时的格式
  * @DateTimeFormat 反序列（json转bean）时的格式
  */
 @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
 @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
 public LocalDateTime createTime;