From: Paul Copeland <[email protected]>
Subject: Re: How do I persist timestamp in UTC timezone?
To: [email protected]
Date: Tuesday, March 17, 2009, 3:04 PM
Of course java.util.Date is already measured in milliseconds
UTC without regard to TimeZone. So it may seem that you are
converting your Date objects to a different timezone, but
that's not the case. This is why you can use
Calendar.compareTo() with objects in different TimeZones.
By definition - new Date() is the same thing as new
Date(System.currentTimeMillis()) no matter what the default
TimeZone!
The link cited by Fazi implies that you have to store the
TimeZone along with the date if you want to load the date
(milliseconds) back into a Calendar object representing that
TimeZone.
If you change the default timezone to UTC (or Moscow, etc.)
then all the other Calendar objects that are meant to
represent the default Locale will be wrong!
- Paul
On 3/17/2009 2:15 PM, Fay Wang wrote:
Hi Fazi,
I found that by putting
TimeZone.setDefault(TimeZone.getTimeZone("Etc/UTC"));
to make your java app in UTC time zone (see below
in testDate), openjpa will store the dates in UTC in the
database.
public void testDate(){
TimeZone.setDefault(TimeZone.getTimeZone("Etc/UTC"));
DateTest dt = new DateTest();
dt.setId(id);
dt.setCreatedTime(Calendar.getInstance(TimeZone.getTimeZone("UTC")));
dt.setStartTime(new Date());
-Fay
--- On Tue, 3/17/09, fazi
<[email protected]> wrote:
From: fazi <[email protected]>
Subject: How do I persist timestamp in UTC
timezone?
To: [email protected]
Date: Tuesday, March 17, 2009, 9:56 AM
Hi
I need to persist all timestamps in UTC timezone.
I found
this documentation
which talks about using Calendar by setting the
timezone
value to the
desired timezone
(http://openjpa.apache.org/builds/1.1.0/apache-openjpa-1.1.0/docs/manual/ref_guide_pc_scos.html#ref_guide_pc_calendar_timezone),
plus this JIRA
(https://issues.apache.org/jira/browse/OPENJPA-322) that
gives me some idea on how I can initialize
Calendar to
insert/update time in
UTC but nothing has worked so far. The timestamps
are
always entered and
read in DB local timezone (PDT). I noticed that
the
Calendar timezone of the
retrieved object is set correctly to UTC, however,
the time
is still in
local timezone (PDT). I also noticed that the
retrieved
object has JPA
implementation of the Calendar object:
org.apache.openjpa.util.java$util$GregorianCalendar$proxy.
We are using openJPA version 1.1.0.
I am copying my artifacts below. The test class
has two
timestamp fields,
one is for UTC timezone and the other one is for
local
timezone to show that
both values are same.
Please let me know if any other information can
help
understand this problem
better.
Any help on this matter will be greatly
appreciated.
---------------------------------------------------------
TestDate table:
CREATE TABLE DATETEST (
ID VARCHAR(255) NOT NULL,
CREATEDTIME TIMESTAMP,
STARTTIME TIMESTAMP)
----------------------------------------------------------
----------------------------------------------------------
JPA class:
----------------------------------------------------------
package com.my.package.entity;
import java.io.Serializable;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
import javax.persistence.*;
@Entity
@Table(name="DATETEST")
public class DateTest implements Serializable {
@Id
@Column(name="ID")
private String id;
@Temporal(TemporalType.TIMESTAMP)
@Column(name="CREATEDTIME")
private Calendar createdTime =
Calendar.getInstance(TimeZone.getTimeZone("UTC"));
@Temporal(TemporalType.TIMESTAMP)
@Column(name="STARTTIME")
private Date startTime;
public Calendar getCreatedTime() {
return createdTime;
}
public void setCreatedTime(Calendar createdTime)
{
this.createdTime = createdTime;
}
public Date getStartTime() {
return startTime;
}
public void setStartTime(Date startTime) {
this.startTime = startTime;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
}
----------------------------------------------------------
----------------------------------------------------------
JUnit test:
----------------------------------------------------------
@Test
public void testDate()
{
DateTest dt = new DateTest();
dt.setId(id);
dt.setCreatedTime(Calendar.getInstance(TimeZone.getTimeZone("UTC")));
dt.setStartTime(new Date());
try
{
//persist
}
catch (Exception e)
{
fail(e.getMessage());
}
// Check result
DateTest returned = null;
try
{
returned = //find by id;
Calendar createdTimeC =
returned.getCreatedTime();
System.out.println("createdTime type
:
" +
createdTimeC.getClass().getName());
System.out.println("createdTime
timezone:
" +
createdTimeC.getTimeZone());
System.out.println("Created time
:
" +
createdTimeC.getTime());
System.out.println("Start time
:
" +
returned.getStartTime());
System.out.println("Created time
(millisecs):
" +
createdTimeC.getTimeInMillis());
System.out.println("Start time
(millisecs) :
" +
returned.getStartTime().getTime());
}
catch (Exception e)
{
fail(e.getMessage());
}
}
----------------------------------------------------------
The output is:
createdTime type :
org.apache.openjpa.util.java$util$GregorianCalendar$proxy
createdTime timezone:
sun.util.calendar.ZoneInfo[id="UTC",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null]
Created time : Tue Mar 17 09:40:39 PDT 2009
Start time : Tue Mar 17 09:40:39 PDT 2009
Created time (millisecs): 1237308039662
Start time (millisecs) : 1237308039662
----------------------------------------------------------
And the DB entry shows:
db2> select * from DATETEST
ID CREATEDTIME
STARTTIME
---------------
----------------------------------
-------------------------------------
utc_test1 2009-03-16-16.14.32.380000
2009-03-16-16.14.32.380000
1 record(s) selected.
db2>
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