Below is my list of json objects:

[
    {
        "Date": "2022-04-06T00:00:00"
    },
    {
        "Date": "2022-12-06T00:00:00"
    }
]

and my POJO:

@Data
public class MyPojo {

    @JsonProperty("Date")
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-mm-dd")
    private Date date;
}

Deserialization code:

public <T> List<T> toObjList(String json, Class<T> className) {
        try {
            return new ObjectMapper().readValue(json, objectMapper.getTypeFactory().constructCollectionType(List.class, className));
        } catch (Exception ex) {
            log.error("Exception converting json to Object: {}", json);
            throw new AppException("Exception while converting String to Object list", ex, HttpStatus.INTERNAL_SERVER_ERROR);
        }
    }

My problem is, despite omitting the time in jsonFormat pattern, I see that some random time is added to each date. I printed the serialized dates and following was the output:

(date=Fri Sep 30 05:30:00 IST 2022)

I tried parsing a date with simleDateFormat and it seemed to parse excluding the time.

String input = "2022-09-30T00:00:00";
SimpleDateFormat parser = new SimpleDateFormat("yyyy-MM-dd");
Date date = parser.parse(input);
System.out.println(date);

This gave an expected output

Fri Sep 30 00:00:00 IST 2022

CodePudding user response：

Avoid legacy date-time classes

The terrible java.util.Date class was years ago supplanted by the modern java.time classes defined in JSR 310.

Among the many flaws in that class, the name Date is a misnomer. The class represents a moment as seen with an offset of zero hours-minutes-seconds from UTC. So it always has a time of day, plus the offset of zero.

java.time.LocalDate

If you want to represent a date-only value, without time of day, and without offset or time zone, use the modern class java.time.LocalDate.

Determining a date from a moment

If you want to get a date from an existing java.util.Date object, immediately convert to its modern replacement, java.time.Instant. Use the new conversion methods added to the old classes.

Instant instant = myJavaUtilDate.toInstant() ; 

To determine a date, you must specify a time zone. For any given moment, the date varies around the globe by time zone. “Tomorrow” in Asia/Tokyo is simultaneously “yesterday” in America/Edmonton.

ZoneId z = ZoneId.of( "Africa/Tunis" ) ;  // Specify your time zone of interest.
ZonedDateTime zdt = instant.atZone( z ) ;

Extract your desired date-only value.

LocalDate ld = zdt.toLocalDate() ; 

Compare LocalDate objects using isEqual, isBefore, and isAfter methods.

Search to learn more. All this has been covered many times on Stack Overflow.

CodePudding user response：

The root cause of the problem is using m instead of M in pattern = "yyyy-mm-dd". The letter M stands for Month in year while m stands for Minute in hour.

Note that the java.util Date-Time API and their parsing/formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern Date-Time API. Learn about the modern date-time API from Trail: Date Time.