Re: How do I persist timestamp in UTC timezone?

Tue, 17 Mar 2009 15:05:09 -0700

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 <faisal.ans...@gmail.com> wrote:


  

From: fazi <faisal.ans...@gmail.com>
Subject: How do I persist timestamp in UTC timezone?
To: users@openjpa.apache.org
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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