What time zone does Hibernate use when it reads and writes a Java Calendar object to an SQL TIMESTAMP?

Question

When Hibernate writes a Java Calendar object to an SQL TIMESTAMP column, to which time zone does it adjust the date, that of the computer or that specified in the calendar object (or some other)?

When Hibernate reads the TIMESTAMP into the calendar object, to which time zone does it translate the date?

Answer 1

When Hibernate writes a Java Calendar object to an SQL TIMESTAMP column, to which time zone does it adjust the date, that of the computer or that specified in the calendar object (or some other)?

Hiberante 3.x uses the following in the CalendarType (see HB-1006):

public void set(PreparedStatement st, Object value, int index) throws HibernateException, SQLException {
    final Calendar cal = (Calendar) value;
    //st.setTimestamp( index,  new Timestamp( cal.getTimeInMillis() ), cal ); //JDK 1.5 only
    st.setTimestamp( index,  new Timestamp( cal.getTime().getTime() ), cal );
}

So Hibernate uses PreparedStatement#setTimestamp(int, Timestamp, Calendar) which uses the time zone of the calendar.

When Hibernate reads the TIMESTAMP into the calendar object, to which time zone does it translate the date?

Well, again, let's look at the CalendarType class:

public Object get(ResultSet rs, String name) throws HibernateException, SQLException {

    Timestamp ts = rs.getTimestamp(name);
    if (ts!=null) {
        Calendar cal = new GregorianCalendar();
        if ( Environment.jvmHasTimestampBug() ) {
            cal.setTime( new Date( ts.getTime() + ts.getNanos() / 1000000 ) );
        }
        else {
            cal.setTime(ts);
        }
        return cal;
    }
    else {
        return null;
    }

}

So Hibernate constructs a default GregorianCalendar using the current time in the default time zone with the default locale.

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As a side note, I highly suggest to read the following question:

• Daylight saving time and Timezone best practices