LocalDateTime，ZonedDateTime和时间戳 [英] LocalDateTime , ZonedDateTime and Timestamp

问题描述

我有一个SpringBoot应用程序.使用Spring Initializer，嵌入式Tomcat，Thymeleaf模板引擎以及作为可执行JAR文件的软件包.

I have a SpringBoot app. using Spring Initializer, embedded Tomcat, Thymeleaf template engine, and package as an executable JAR file.

我有一个具有2个属性(initDate，endDate)的域对象.我想创建2个转换器来处理mySQL DB

I have a domain object with 2 properties (initDate, endDate). I want to create 2 converters to deal with mySQL DB

@Convert(converter = LocalDateTimeAttributeConverter.class) 
private LocalDateTime initDate;

@Convert(converter = ZonedDateTimeAttributeConverter.class) 
private ZonedDateTime endDate;

转换器1(可以)

@Converter
public class LocalDateTimeAttributeConverter implements AttributeConverter<LocalDateTime, Timestamp> {

    @Override
    public Timestamp convertToDatabaseColumn(LocalDateTime localDateTime) {
        return (localDateTime == null ? null : Timestamp.valueOf(localDateTime));
    }

    @Override
    public LocalDateTime convertToEntityAttribute(Timestamp sqlTimestamp) {
        return (sqlTimestamp == null ? null : sqlTimestamp.toLocalDateTime());
    }
}

这是我要创建的那个

@Converter
public class ZonedDateTimeAttributeConverter implements AttributeConverter<ZonedDateTime, Timestamp> {

    @Override
    public Timestamp convertToDatabaseColumn(ZonedDateTime zoneDateTime) {
        return (zoneDateTime == null ? null : Timestamp.valueOf(zoneDateTime));
    }


    @Override
    public ZonedDateTime convertToEntityAttribute(Timestamp sqlTimestamp) {
        return (sqlTimestamp == null ? null : sqlTimestamp.toZonedDateTime());
    }
}

但是我不能，因为我有两个错误:

But I can't because I have 2 errors:

The method valueOf(String) in the type Timestamp is not applicable for the arguments (ZonedDateTime)

，并且时间戳记没有方法toZonedDateTime()

and the TimeStamp does not have the method toZonedDateTime()

如果我不为ZonedDate添加任何转换器，JPA将创建一个类型为varbinary(255)

and if I don't add any converter for the ZonedDate, JPA creates a table with the type varbinary(255)

推荐答案

时间戳扩展了Date以提供纳秒级的精度. Date和Timestamp都没有设计为将特定时区称为ZoneDateTime.

Timestamp extends Date to provide nanosecond accuracy. Neither Date nor Timestamp are designed to refer to a specific timezone as ZoneDateTime.

如果需要转换ZonedDateTime-> Timestamp，则必须放弃时区/偏移量信息.例如

If you need to convert ZonedDateTime -> Timestamp you will have to discard the timezone/offset information. E.g.

LocalDateTime withoutTimezone = zoneDateTime.toLocalDateTime();
Timestamp timestamp = Timestamp.valueOf(withoutTimezone));

，要转换Timestamp-> ZonedDateTime，您需要指定一个偏移量:

and for converting Timestamp -> ZonedDateTime you need to specify an offset:

LocalDateTime withoutTimezone = sqlTimestamp.toLocalDateTime();
ZonedDateTime withTimezone = withoutTimezone.atZone(ZoneId.of("+03:00"));

或时区:

ZonedDateTime withTimezone = withoutTimezone.atZone(ZoneId.of("Europe/Paris"));

如果您打算将ZonedDateTime变量保存在数据库中并保留在那里指定的各个时区，则建议相应地设计数据库.建议:

If your intention is to save ZonedDateTime variables in the database and preserve the various timezones specified there, I recommend designing your database accordingly. Suggestions:

1. 使用类型为DATETIME的列保存LocalDateTime和VARCHAR保存时区，如"Europe/Paris"或SMALLINT保存以分钟为单位的偏移量.
2. 将ZonedDateTime转换为String，并保存在VARCHAR列中，例如"2017-05-16T14:12:48.983682+01:00[Europe/London]".然后，当您从数据库中读取数据时，必须对其进行解析.

1. Use a column of type DATETIME to save a LocalDateTime and a VARCHAR saving a timezone like "Europe/Paris" or a SMALLINT saving an offset in minutes.
2. Convert the ZonedDateTime to a String and save in a VARCHAR column like "2017-05-16T14:12:48.983682+01:00[Europe/London]". You'll then have to parse it when reading from the database.

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