CODEWITHSUNDEEP
javajsongson
Daniel Calderon Mori
Daniel Calderon Mori

Reputation: 5776

How to parse both Date and Time in using gson?

I have a json input that contains the following fields (among others):

...
leadDate: "2016-01-16",
leadTime: "13:45:22",
...

I'm trying to parse this json using Gson library to set them to the following Java attributes:

private Date leadDate;
private Time leadTime;

but the setDateFormat method doesn't allow me to set both date format and time format without the use of DateFormat constants. And these, as far as I know, doesn't include the formats I need.

What can I do if I have to use Gson?

Upvotes: 3

Views: 2130

Answers (2)

Basil Bourque
Basil Bourque

Reputation: 338775

No Date-Time Types In JSON

JSON lacks any date-time data types. So the format and meaning of your Strings is up to you and your data supplier/consumer.

Use java.time Classes

Avoid the old date-time classes bundled with the earliest versions of Java such as java.util.Date/.Calendar. They are notoriously troublesome. In Java 8 and later they have been officially supplanted by the java.time framework.

Converters

Gson has converters for serializers/deserializers to handle the chore of dehydrating and rehydrating java.time objects. See: Gson Type Adapters for Common Classes. Or consider writing your own. Such serialization tools would do something like the following.

Parsing

Your date and time are separate. Start by parsing each as LocalDate and LocalTime. Both your String inputs comply with the ISO 8601 standard defining formats of Strings representing date-time values. That is handy as the java.time classes use this standard as their defaults when parsing or generating such Strings.

LocalDate localDate = LocalDate.parse( "2016-01-16" );
LocalTime localTime = LocalTime.parse( "13:45:22" );

Time Zone

Both LocalDate and LocalTime are date-only and time-only respectively, and both lack any time zone or offset-from-UTC information. Such time zone information is critical to making sense of your date-time data. Does your example data mean a quarter until two in the afternoon of Paris, Montreal, or Tokyo? Perhaps you have additional fields of data with this zone/offset info, or perhaps in your context you can assume the time zone.

ZoneId zoneId = ZoneId.of( "America/Montreal" );

Let's apply that time zone to our date-only and time-only to get a full-fledged date-time, an actual moment on the timeline.

ZonedDateTime zdt = ZonedDateTime.of( localDate , localTime , zoneId );

String Output

You can output in ISO 8601 compliant string by simply calling toString. Actually, java.time extends the ISO 8601 format by appending the name of the time zone in brackets.

2016-01-16T13:45:22-05:00[America/Montreal]

To generate Strings in other formats, search StackOverflow.com for many examples of java.time.format package.

Instant

Generally the best practice is to do your business logic and data storage/exchange all in UTC. In java.time that means the Instant class which represents a moment on the timeline in UTC. We can instantiate an Instant object from our ZonedDateTime.

Instant instant = zdt.toInstant();

Upvotes: 2

pratapvaibhav19
pratapvaibhav19

Reputation: 222

java.sql.Date and java.sql.Time have already built-in methods for doing it. Simply read the data from json file and pass it in valueOf method like this--

  1. In the case of leadDate-
    Date.valueOf(value of leadDate);

  2. In the case of leadTime-
    Time.valueOf(value of leadTime);

Upvotes: 0

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