[Kotlin][SpringBoot3] 시간 데이터 LocalDateTime ↔ unix timestamp ↔ string 변환하기 & 현재시간 여러 데이터 타입으로 출력하기

 

 - 시간 기본 포맷 예제 String 표기

"yyyy-MM-dd HH:mm:ss.SSS"

 

 

 

 

 

1. 현재 시간을 unix timestamp로 확보하기

 

import java.time.Instant

fun getCurrentUnixTimestamp(): Long {
    return Instant.now().epochSecond
}

// ##################################################

fun main() {
    val currentUnixTimestamp = getCurrentUnixTimestamp()
    println("Current Unix Timestamp: $currentUnixTimestamp")
}

 

 

 

 

 

2. 현재 시간을 LocalDateTime으로 확보하기

 

LocalDateTime.now()

import java.time.LocalDateTime
import java.time.ZoneOffset

fun getCurrentLocalDateTime(): LocalDateTime {
    return LocalDateTime.now(ZoneOffset.UTC)
}


// ##################################################

fun main() {
    val currentLocalDateTime = getCurrentLocalDateTime()
    println("Current LocalDateTime: $currentLocalDateTime")
}

 

 - 한국 서울 현재 시간 가져오기

import java.time.LocalDateTime
import java.time.ZoneId


data = LocalDateTime.now(ZoneId.of("Asia/Seoul"))

 

 

 

 

 

 

3. 현재 시간을 String으로 확보하기

 

import java.time.LocalDateTime
import java.time.ZoneOffset
import java.time.format.DateTimeFormatter

fun getCurrentDateTimeAsString(): String {
    val currentLocalDateTime = LocalDateTime.now(ZoneOffset.UTC)
    val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")
    return currentLocalDateTime.format(formatter)
}


// Recommendation
import java.time.LocalDateTime
import java.time.ZoneId
import java.time.format.DateTimeFormatter

fun getCurrentKstTimeAsString(): String {
    val currentLocalDateTime = LocalDateTime.now(ZoneId.of("Asia/Seoul"))
    val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")
    return currentLocalDateTime.format(formatter)
}

 

import java.time.Instant
import java.time.ZoneOffset
import java.time.format.DateTimeFormatter

fun currentUnixTimestampToString(): String {
    val currentUnixTimestamp = Instant.now().epochSecond
    val formatter = DateTimeFormatter.ISO_DATE_TIME
    return formatter.format(Instant.ofEpochSecond(currentUnixTimestamp).atOffset(ZoneOffset.UTC))
}

 

 

 

 

 

4. LocalDateTime → unix timestamp & string

 

 - LocalDateTime → Unix Timestamp

import java.time.Instant
import java.time.LocalDateTime
import java.time.ZoneOffset

fun localDateTimeToUnixTimestamp(localDateTime: LocalDateTime): Long {
    return localDateTime.toInstant(ZoneOffset.UTC).epochSecond
}

import java.time.LocalDateTime
import java.time.ZoneOffset

fun customDateTimeToUnixTimestamp(year: Int, month: Int, day: Int, hour: Int, minute: Int, second: Int): Long {
    val customDateTime = LocalDateTime.of(year, month, day, hour, minute, second)
    return customDateTime.toInstant(ZoneOffset.UTC).epochSecond
}

 

 - LocalDateTime → String

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

fun localDateTimeToString(localDateTime: LocalDateTime): String {
    val formatter = DateTimeFormatter.ISO_DATE_TIME // ISO 8601 형식 - ex. 2020-07-10 15:00:00.000
    return localDateTime.format(formatter)
}

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

fun localDateTimeToStringWithFormat(localDateTime: LocalDateTime, format: String): String {
    val formatter = DateTimeFormatter.ofPattern(format)	// format 사용자 지정
    return localDateTime.format(formatter)
}

import java.time.LocalDateTime
import java.time.format.DateTimeFormatter
import java.util.Locale

fun localDateTimeToStringWithLocale(localDateTime: LocalDateTime, format: String, locale: Locale): String {
    val formatter = DateTimeFormatter.ofPattern(format, locale) // 포맷 사용자 지정 및 로케일 설정
    return localDateTime.format(formatter)
}

import java.time.LocalDateTime
import java.time.ZoneId
import java.time.format.DateTimeFormatter

fun localDateTimeToStringWithZone(localDateTime: LocalDateTime, format: String, zoneId: String): String {
    val formatter = DateTimeFormatter.ofPattern(format)
    val zonedDateTime = localDateTime.atZone(ZoneId.of(zoneId))	// 커스텀 포맷 및 시간대 설정
    return zonedDateTime.format(formatter)
}

 

 

 

 

 

5. unix timestamp → LocalDateTime & string

 

 - unix timestamp → LocalDateTime

import java.time.Instant
import java.time.LocalDateTime
import java.time.ZoneOffset

// 일반적인 예시
fun unixTimestampToLocalDateTime(unixTimestamp: Long): LocalDateTime {
    return LocalDateTime.ofInstant(Instant.ofEpochSecond(unixTimestamp), ZoneOffset.UTC)
}

// 한국 시간으로 바꾸는 일반적인 예시
fun unixTimestampToLocalDateTime(unixTimestamp: Long): LocalDateTime {
    return LocalDateTime.ofInstant(Instant.ofEpochSecond(unixTimestamp), ZoneId.of("Asia/Seoul"))
}

import java.time.Instant
import java.time.LocalDateTime
import java.time.ZoneId

// 다른 타임존 적용
fun unixTimestampToLocalDateTimeWithZone(unixTimestamp: Long, zoneId: String): LocalDateTime {
    return LocalDateTime.ofInstant(Instant.ofEpochSecond(unixTimestamp), ZoneId.of(zoneId))
}

import java.time.LocalDateTime

// 직접 계산하기
fun extractUnixTimestampParts(unixTimestamp: Long): LocalDateTime {
    val year = unixTimestamp / 31536000L // 1년의 초
    val remainingSeconds = unixTimestamp % 31536000L
    val month = remainingSeconds / 2592000L // 1달의 초
    val day = (remainingSeconds % 2592000L) / 86400L // 1일의 초
    val hour = (remainingSeconds % 86400L) / 3600L // 1시간의 초
    val minute = (remainingSeconds % 3600L) / 60L // 1분의 초
    val second = remainingSeconds % 60L // 초

    return LocalDateTime.of(year.toInt(), month.toInt(), day.toInt(), hour.toInt(), minute.toInt(), second.toInt())
}

 

 - unix timestamp → String

import java.time.Instant
import java.time.ZoneOffset
import java.time.format.DateTimeFormatter

// 기본 포맷 사용
fun unixTimestampToString(unixTimestamp: Long): String {
    val instant = Instant.ofEpochSecond(unixTimestamp)
    val formatter = DateTimeFormatter.ISO_DATE_TIME // 또는 원하는 포맷 선택
    return formatter.format(instant.atOffset(ZoneOffset.UTC))
}

import java.time.Instant
import java.time.ZoneOffset
import java.time.format.DateTimeFormatter

// 사용자 정의 포맷 - UTC
fun unixTimestampToStringWithFormat(unixTimestamp: Long, format: String): String {
    val instant = Instant.ofEpochSecond(unixTimestamp)
    val formatter = DateTimeFormatter.ofPattern(format)
    return formatter.format(instant.atOffset(ZoneOffset.UTC))
}

// 사용자 정의 포맷	"yyyy-MM-dd HH:mm:ss"
fun unixTimestampToKSTStringWithFormat(unixTimestamp: Long, format: String): String {
    val dateTime = Instant.ofEpochSecond(unixTimestamp).atZone(ZoneId.of("Asia/Seoul")).toLocalDateTime()
    val formatter = DateTimeFormatter.ofPattern(format)
    return dateTime.format(formatter)
}

import java.time.Instant
import java.time.ZoneId
import java.time.format.DateTimeFormatter

// 시간대 설정
fun unixTimestampToStringWithZone(unixTimestamp: Long, zoneId: String): String {
    val instant = Instant.ofEpochSecond(unixTimestamp)
    val formatter = DateTimeFormatter.ISO_DATE_TIME
    return formatter.format(instant.atZone(ZoneId.of(zoneId)).toOffsetDateTime())
}

 

 

 

 

 

6. string → LocalDateTime & unix timestamp

 

 - to LocalDateTime

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

fun stringToLocalDateTime(dateTimeStr: String): LocalDateTime {
    val formatter = DateTimeFormatter.ISO_DATE_TIME // 또는 원하는 포맷 선택
    return LocalDateTime.parse(dateTimeStr, formatter)
}

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

fun stringToLocalDateTimeWithFormat(dateTimeStr: String, format: String): LocalDateTime {
    val formatter = DateTimeFormatter.ofPattern(format)	// 사용자 정의 포맷
    return LocalDateTime.parse(dateTimeStr, formatter)
}

import java.time.LocalDateTime
import java.time.format.DateTimeFormatter
import java.util.Locale

fun stringToLocalDateTimeWithLocale(dateTimeStr: String, format: String, locale: Locale): LocalDateTime {
    val formatter = DateTimeFormatter.ofPattern(format, locale)
    return LocalDateTime.parse(dateTimeStr, formatter) // 사용자 정의 포맷 및 로케일 설정
}

import java.time.LocalDateTime
import java.time.ZoneId
import java.time.ZonedDateTime
import java.time.format.DateTimeFormatter

fun stringToLocalDateTimeWithZone(dateTimeStr: String, zoneId: String): LocalDateTime {
    val formatter = DateTimeFormatter.ISO_DATE_TIME
    val zonedDateTime = ZonedDateTime.parse(dateTimeStr, formatter.withZone(ZoneId.of(zoneId)))	// 시간대 설정
    return zonedDateTime.toLocalDateTime()
}

 

 - to Unix Timestamp : UTC 기준

import java.time.LocalDateTime
import java.time.ZoneOffset

fun stringToUnixTimestamp(dateTimeStr: String): Long {
    val localDateTime = LocalDateTime.parse(dateTimeStr)
    return localDateTime.toEpochSecond(ZoneOffset.UTC)
}

import java.time.LocalDateTime
import java.time.ZoneOffset
import java.time.format.DateTimeFormatter

fun stringToUnixTimestampWithFormat(dateTimeStr: String, format: String): Long {
    val formatter = DateTimeFormatter.ofPattern(format)	// 사용자 정의 포맷 사용
    val localDateTime = LocalDateTime.parse(dateTimeStr, formatter)
    return localDateTime.toEpochSecond(ZoneOffset.UTC)
}

import java.time.ZonedDateTime
import java.time.ZoneId
import java.time.format.DateTimeFormatter

fun stringToUnixTimestampWithZone(dateTimeStr: String, zoneId: String): Long {
    val formatter = DateTimeFormatter.ISO_DATE_TIME
    val zonedDateTime = ZonedDateTime.parse(dateTimeStr, formatter.withZone(ZoneId.of(zoneId)))	// 시간대 설정
    return zonedDateTime.toEpochSecond()
}

 - to Unix Timestamp : KST 기준

import java.time.Instant
import java.time.LocalDateTime
import java.time.ZoneId
import java.time.format.DateTimeFormatter

fun kstStringToUnixTimestampUsingJavaTime(kstString: String): Long {
    val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")
    val dateTime = LocalDateTime.parse(kstString, formatter)
    val instant = dateTime.atZone(ZoneId.of("Asia/Seoul")).toInstant()
    return instant.epochSecond
}

fun main() {
    val kstString = "2023-09-18 15:30:00" // 원하는 KST 문자열 시간
    val unixTimestamp = kstStringToUnixTimestampUsingJavaTime(kstString)
    
    println("KST String: $kstString")
    println("Unix Timestamp: $unixTimestamp")
}

import java.text.SimpleDateFormat
import java.util.*

fun kstStringToUnixTimestamp(kstString: String): Long {
    val dateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
    dateFormat.timeZone = TimeZone.getTimeZone("Asia/Seoul")
    
    try {
        val date = dateFormat.parse(kstString)
        return date.time / 1000 // 밀리초를 초로 변환
    } catch (e: Exception) {
        throw IllegalArgumentException("Invalid KST string format: $kstString")
    }
}

fun main() {
    val kstString = "2023-09-18 15:30:00" // 원하는 KST 문자열 시간
    val unixTimestamp = kstStringToUnixTimestamp(kstString)
    
    println("KST String: $kstString")
    println("Unix Timestamp: $unixTimestamp")
}