JPA Date and Timezone confusion - date

Question

I'm having a problem reading dates from a database using JPA. I'm using EclipseLink and PostgreSQL
I've populated my database from a CSV file, witch had dates as strings (in this format: 6/30/2009-23:59:56). I used the following snipet to convert it to a Date object:
public static Date parseDate(String s){
DateFormat formatter = new SimpleDateFormat("d/M/yyyy-k:m:s");
try {
return new Date( ((java.util.Date)formatter.parse(s)).getTime() );
} catch (ParseException ex) {
Logger.getLogger(Type.class.getName()).log(Level.SEVERE, null, ex);
return null;
}
}
The date is correctly converted and stored in the database as expected. Here is how i map the Date object to the database:
#Column(name="data_ts", nullable=false)
#Temporal(TemporalType.TIMESTAMP)
private Date dataTs;
The problem seems to happen when i try to read the Date from the database to use it in a chart(Highcharts). The record with that same timestamp above get read as:
Mon Jun 06 23:59:56 BRT 2011 and it's timestamp as 1307415596000
Note that it is in Brazilian Time(+3h), so the timestamp (that is calculated from GMT) is 3 hours shifted. Once ploted, the timestamp turns to point to 07/06/2011 02:59:56
Here's an example:
List<TimedataEnt> timeData = currentWellsite.getTimeData();
String debug = timeData.get(timeData.size()-1).getDataTs().toString() + ">>>" + timeData.get(timeData.size()-1).getDataTs().getTime();
where currentWellsite is and JPA Entity, and getDataTs() returns a java.util.Date object.
The string turns out to be "Tue Jun 30 23:59:56 BRT 2009>>>1246417196000"
How do I tell JPA not to convert the timestamp read from the database?

Answer 1

As said, Date and Timestamps have no timezone consideration. It seems that the issue is caused because Java considers that the time it reads from the database is the current default timezone.
So, if the database contais 2011-04-04 14:00:00 and my current timezone is +3, assigning that to java Date will generate 2011-04-04 14:00:00 BRT time(+3), with a timestamp shifted 3 hours (since timestamps are caclulated from UTC).
Solved the issue by getting an calculated timestamp:
long ts = myDate().getTime() + TimeZone.getDefault().getRawOffset();
It's important to say that getRawOffset() does not take Daylight Saving periods in consideration. For that, use getOffset()

Answer 2

Your date is 6/30/2009-23:59:56. I read that as 30 june 2009, 23:59:56. So the format to parse it should be M/d/yyyy-HH:mm:ss or M/d/yyyy-kk:mm:ss (depending on if your hours go from 1 to 24 or from 0 to 23). But definitely not d/M/yyyy-k:m:s: the month comes before the day.
Also, a Timestamp doesn't have any time zone. It's a universal instant in time. It's only when you display its value that the timezone is important, because then you have to choose which time zone to use to display the time. Use a DateFormat with the appropriate timezone set to display your timestamp.

Answer 3

Your issue seems to be that you are storing your Timestamp (which does not have a timezone) into a java.util.Date (which has a timezone offset).
If you want control over how the timezone is set, then store your Timestamp as a java.sql.Timestamp, or use your own #Converter.
In general Calendar should be used in Java instead of java.util.Date, which is for the most part deprecated. Calendar also has a Timezone, so you may have similar issues.