Java本地时区问题

Question

I have a scenario where i am missing some hours data based on the local timezone. Datastore is having records in UTC. Lets assume the the local timezone is "Asia/Kolkata". User have some options to choose between dates and report will be generated for those dates in the UI. For each day user will see a count in that day starting from first hour to last hour. Lets user have entered Jan 22nd to feb 12th on the UI, then, then the query will be fire between these date inclusive of both dates starting from 00:00 hours to ending 23:00 Hours with given a result set in UTC. I have a code snippet where this result set will be converted to local timezone as below mentioned.

java.util.Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("Asia/Kolkata")); 
java.sql.Timestamp ts = resultSet.getTimestamp(PUBLISH_TIME, cal);

Becuase of this, the end resultset miss some hours data due to local timezone ie on Jan 22nd(The other days count is correct except this starting day) i will get the data from 05:30 hours not from 00:00 Hours of the day. If i have the UTC set in the resultset calendar instance then i am getting all hours data without any miss.

Is this the correct behavior?

I also tried querying the DB with local timezone with the help of below snippet but it also gives the wrong counts. I am not sure whether i need to do this at the query time but you can see the below snippet?

 SimpleDateFormat localTimeFormatter = new SimpleDateFormat("yyyy-MM-dd  HH:mm:ss.SSS");
localTimeFormatter.setTimeZone(TimeZone.getTimeZone("Asia/Kolkata"));
SimpleDateFormat utcFormatter = new SimpleDateFormat(DateUtil.DATE_PATTERN);
utcFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
Date startDateUTC;
String startDateUTCString;
Date endDateUTC;
String endDateUTCString;
try {
    startDateUTC = localTimeFormatter.parse(reportCriteria.getStartDate());
    startDateUTCString = utcFormatter.format(startDateUTC);


    endDateUTC = localTimeFormatter.parse(reportCriteria.getEndDate());
    endDateUTCString = utcFormatter.format(endDateUTC);

} catch (ParseException e) {
    e.printStackTrace();
    log.error("Error while formating Date :" + e);    

How can get the missed hours data in local timezone? I am not using joda time and i do not want to use that now with using java7.

Answer 1

Lets user have entered Jan 22nd to feb 12th on the UI, then, then the query will be fire between these date inclusive of both dates starting from 00:00 hours to ending 23:00 Hours with given a result set in UTC.

To me this sounds like you are using a range of local timestamps, provided by a user, to query a table containing UTC timestamps, ignoring the different timezones. You need to convert local timestamps to UTC first and use the converted value to query the database.

If you don't things go wrong.

Eg say the table contains a record with the timestamp Jan 22nd 23:00 (UTC) . When you query the table using the local timestamp Jan 23nd 00:00 (UTC+1) , you are not going to get that record out even though they're exactly the same.

In your case, the Asia/Kolkata timezone is equal to UTC+5:30. So if the database is queried for the UTC timestamp Jan 1st 00:00 and afterwards the result is converted to a local datetime, the result Jan 1st 00:00 becomes Jan 1st 05:30.