CODEWITHSUNDEEP
javaoracle-databasejdbctimetype-conversion
user11147380
user11147380

Reputation:

DB and java time date comparison and conversion

I am getting a variable newValue in java as 

public void reTrigger() {
    Date date1 = new Date();
   SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH.mm.ss");

    squery: "select newValue from SAVE_TXN WHERE ROWID = 1"
(newValue is of type nvarchar2)

    String vidtime = sdf.format(parser.getValueOf("newValue")); //parser is another method which parses the squery 
String currentDate = sdf.format(date1);
}

Now newvalue contains date and time like: '2020/05/17 18.30.44' in DB, which I am fetching into vidtime.

Now I want to subtract this vidtime with currentDate in java and check whether it is greater than or equals to 120 hours or not. How to proceed ?

Upvotes: 0

Views: 579

Answers (2)

Basil Bourque
Basil Bourque

Reputation: 338730

You are using terrible date-time classes that were years ago supplanted by the modern java.time classes with the adoption of JSR 310.

You should be retrieving date-time values from the database as date-time objects rather than strings. As of JDBC 4.2, we can exchange java.time classes with the database. See PreparedStatement::setObject and ResultSet::getObject.

For a database column of type:

  • TIMESTAMP WITH TIME ZONE, retrieve as a OffsetDateTime (support for the more commonly used Instant and ZonedDateTime classes was unfortunately and mysteriously omitted from JDBC 4.2).

  • TIMESTAMP WITHOUT TIME ZONE, retrieve as a LocalDateTime.

If faced with a string input, parse using DateTimeFormatter class.

Your input lacks an indicator of time zone or offset-from-UTC. So we must parse as a LocalDateTime. 

DateTimeFormatter f = DateTimeFormatter.ofPattern(  "uuuu/MM/dd HH.mm.ss" ) ;
LocalDateTime ldt = LocalDateTime.parse( input , f ) ;

Capturing the current moment requires a time zone. For any given moment, the date and the time-of-day vary around the globe by zone. 

ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime now = ZonedDateTime.now( z ) ;

We cannot compare this current moment (zdt) to your input, the ldt. Your input and a LocalDateTime object do not represent a moment, are not a specific point on the timeline. Take your example, 2020/05/17 18.30.44. We cannot know if that means 6:30 PM on the 17th in Tokyo, in Toulouse, or in Toledo – all different moments, several hours apart on the timeline.

So your Question as written cannot be solved.

If you know for certain that a time zone was intended for your input string, apply a time zone to produce a ZonedDateTime. 

ZoneId zIntended = ZoneOf.( "Africa/Tunis" ) ;
ZonedDateTime then = ldt.atZone( zIntended ) ;

Calculate elapsed time as a Duration.

Duration d = Duration.between( now , then ) ;
if( d.toHours() > 120 ) { … }

Upvotes: 3

Khalid El Boukhari
Khalid El Boukhari

Reputation: 34

Maybe something like this :

import java.time.Duration;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
public class Test {
    public static void main(String[] args) {
        final LocalDateTime now = LocalDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        final LocalDateTime dateToCompare = LocalDateTime.parse("2020-05-28 02:05:45",formatter);
        final long hours = Duration.between(now, dateToCompare).toHours();
        System.out.print(hours);
    }
}

Upvotes: 1

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