Remap one date format to another in Java model

Question

1) The date format I'm getting from API is yyyy-MM-dd'T'HH:mm:ss.SSSXXX

2) I want to give back a Json list with dates to frontend in different format like: dd MM HH:mm

Is there any annotations or properties to remap dates in 2) example as in 1) it's easily achievable with @JsonFormat.

Answer 1

Offset-from-UTC

The XXX in your formatting pattern refers to an offset-from-UTC. This means the date and time-of-day represent a moment that is a number of hours-minutes-seconds ahead of, or behind, the baseline of UTC.

OffsetDateTime

So parse that input with OffsetDateTime.

OffsetDateTime odt = OffsetDateTime.parse( "2019-01-23T12:34:56.123+05:30" ) ;

Do not be mislead into using the LocalDateTime class for such inputs. This class purposely lacks any concept of time zone or offset-from-UTC. So this class cannot be used to represent a moment. Parsing your inputs with this class is recklessly discarding valuable information. See: What's the difference between Instant and LocalDateTime?

DateTimeFormatter

To generate strings representing this value in standard ISO 8601 format, merely call toString.

String output = odt.toString() ;  // Generate string in standard ISO 8601 format.

To generate strings in other formats, use the DateTimeFormatter class. You can specify a custom format, or better, let the class automatically localize for you.

To localize, specify:

• FormatStyle to determine how long or abbreviated should the string be.
• Locale to determine:
  • The human language for translation of name of day, name of month, and such.
  • The cultural norms deciding issues of abbreviation, capitalization, punctuation, separators, and such.

Example:

Locale l = Locale.CANADA_FRENCH ;   // Or Locale.US, Locale.JAPAN, etc.
DateTimeFormatter f = 
    DateTimeFormatter
    .ofLocalizedDateTime( FormatStyle.FULL )
    .withLocale( l )
;
String output = zdt.format( f );

Search Stack Overflow for more info, as DateTimeFormatter has already been covered many many times.

ISO 8601

Your input strings happen to be in standard ISO 8601 format.

The java.time classes use these standard formats by default when parsing/generating strings. So no need to specify a formatting pattern.

---

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.

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

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

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - 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
  • Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). 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.

Answer 2

You can add some logic in getter (e.g. getDate()) like there:

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class Main {
    public static void main(String[] args) {
        String inputDate = "2014-07-04T12:08:56.235-07:00";
        String inputFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXX";

        String outputFormat = "dd MM HH:mm";

        // Input formatter
        DateTimeFormatter inputFormatter = DateTimeFormatter.ofPattern(inputFormat);

        // Time after formatting
        LocalDateTime dateTime = LocalDateTime.parse(inputDate, inputFormatter);

        // Output formatter
        DateTimeFormatter outputFormatter = DateTimeFormatter.ofPattern(outputFormat);

        // Output date as String
        String outputDate = dateTime.format(outputFormatter);

        System.out.println(outputDate);
    }
}