使用postgres的TimeZone将日期转换为时间戳

Question

I have postgresql time column with type TIMESTAMP WITH TIME ZONE having a sample value like 1970-01-01 00:00:00+05:30 I want to compare a value with Date value like:

Date date = new Date(0L);

ie Tue Jan 19 13:55:24 IST 2016

So I used

Timestamp timeStampDate = new Timestamp(date.getTime());

The above code gives timeStampDate.getTime() as 0.

How to convert it in the above format so that it can be compared, Currently comparing is giving no results. How to format this date.

I basically want to convert " Date is Thu Jan 01 05:30:00 IST 1970 " to this format : "1970-01-01 00:00:00+05:30"

Answer 1

java.time

If your database driver supports JDBC 4.2 or later, use Instant to get data from your database where stored in a TIMESTAMP WITH TIME ZONE column.

Instant instant = myResultSet.getObject( … , Instant.class ) ;

For an older JDBC driver, use java.sql.Timestamp to get data from your database by calling getTimestamp on your ResultSet . That Timestamp object is in UTC. Postgres stores your TIMESTAMP WITH TIME ZONE in UTC, by the way, and loses the original time zone or offset-from-UTC that came with the incoming data after using that data to adjust into UTC as part of the storage process.

You should convert your java.sql.Timestamp/.Date/.Time to java.time types as soon as possible. Then proceed with your business logic.

In a nutshell, java.time is… An Instant is a moment on the timeline in UTC. Apply a time zone ( ZoneId ) to get a ZonedDateTime .

Convert To java.time

So convert from Timestamp, get an Instant, apply a ZoneId.

java.sql.Timestamp ts = myResultSet.getTimestamp( 1 );
…
Instant instant = ts.toInstant();

Specify your desired/expected time zone. Apply to the Instant.

ZoneId zoneId = ZoneId.of( "Asia/Kolkata" );
ZonedDateTime zdt = ZonedDateTime.ofInstant( instant , zoneId );

Comparison

Get the current moment, for use in comparison.

ZonedDateTime now = ZonedDateTime.now( zoneId );

Compare by calling the isEqual , isBefore , or isAfter methods.

Boolean beforeNow = zdt.isBefore( now );

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About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date , Calendar , & SimpleDateFormat .

The Joda-Time project, now in maintenance mode , advises migration to the java.time classes.

To learn more, see the Oracle Tutorial . And search Stack Overflow for many examples and explanations. Specification is JSR 310 .

Where to obtain the java.time classes?

• Java SE 8 , Java SE 9 , and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport .
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP… .

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval , YearWeek , YearQuarter , and more .