springboot Right value of LocalDate isn't saved to data base when JST Server and uses JDBC

When system running JVM uses JST (or perhaps happen in not UTC system), LocalDate column is not saved right value to database (MySQL). It is one day ago date. I use JDBC.

I investigate this symptom, I found some things.

In spring boot, when write to database, LocalDate is converted to Date and its locale is system's.

        // in BasicRelationalPersistentProperty.java
    private static final Map<Class<?>, Class<?>> javaToDbType = new LinkedHashMap<>();

    static {

        javaToDbType.put(Enum.class, String.class);
        javaToDbType.put(ZonedDateTime.class, String.class);
        javaToDbType.put(Temporal.class, Date.class);
    }

        // in Jsr310Converters.java
    @WritingConverter
    public static enum LocalDateToDateConverter implements Converter<LocalDate, Date> {

        INSTANCE;

        @Nonnull
        @Override
        public Date convert(LocalDate source) {
            return Date.from(source.atStartOfDay(systemDefault()).toInstant());
        }
    }

But, when Date is converted to String to build query, JDBC uses US locale. It sometimes mismatches to origin Date 's TZ. (This code may not be in spring-boot)

    // in com.mysql.cj.util.TimeUtil.java
    public static SimpleDateFormat getSimpleDateFormat(SimpleDateFormat cachedSimpleDateFormat, String pattern, Calendar cal, TimeZone tz) {
        SimpleDateFormat sdf = cachedSimpleDateFormat != null ? cachedSimpleDateFormat : new SimpleDateFormat(pattern, Locale.US); // here(cachedSimpleDateFormat is null in the first and initialize here.)

        if (cal != null) {
            sdf.setCalendar((Calendar) cal.clone()); // cloning the original calendar to avoid it's modification
        }

        if (tz != null) {
            sdf.setTimeZone(tz);
        }
        return sdf;
    }

So, I suggest to prepare LocalDateToStringConverter not to be affected system. Because LocalDate dosen't have locale, LocalDate should not be converted to Date which has locale.

Comment From: bclozel

This code lives in Spring Data Commons, so this can't be fixed in Spring Boot directly.

Could you create an issue on the relevant tracker please? Unfortunately, I can't transfer this issue automatically as Spring Data is not using GitHub for issues.

Thanks!

Comment From: sasurai-usagi3

[NOTE] I notice this code can resolve this problem.

package hoge

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import java.util.*

@SpringBootApplication
class HogeApplication

fun main(args: Array<String>) {
    TimeZone.setDefault(TimeZone.getTimeZone("UTC")) // add this code
    runApplication<HogeApplication>(*args)
}