jackson/json schema - replacing ISO8601Utils with the external json schema generator module

I am replacing ISO8601Utils which is commented below due to SonarQube throwing the following error: Remove this use of "ISO8601Utils"; it is deprecated. To replace it, I would use the external json schema generator module, https://github.com/FasterXML/jackson-module-jsonSchema or something else. I read through the link, but don't understand how to use object mapper to turn to replace this line: String value = ISO8601Utils.format(date, true);

    public static class ISO8601DateFormat extends DateFormat {

    public ISO8601DateFormat() {}

    public StringBuffer format(Date date, StringBuffer toAppendTo,
            FieldPosition fieldPosition) {
        String value = ISO8601Utils.format(date, true);
        //Im not sure how I can replace this line with a new
        //replacement

        toAppendTo.append(value);
        return toAppendTo;
    }

    public Date parse(String source, ParsePosition pos) {
        pos.setIndex(source.length());
        return ISODateTimeFormat.dateTimeParser().parseDateTime(source).toDate();
    }

    public Object clone() {
        return this;
    }

    public String toString() {
        return this.getClass().getName();
    }
}

Any help would be greatly appreciated!

P.S. I am writing a unit test to verify that both the ISO8601Utils and SimpleDateFormat has the same format.

My updated class:

    public static class ISO8601DateFormat extends DateFormat {

    public static final long serialVersionUID = 3549786448500970210L;

    public ISO8601DateFormat() {}

    @Override
    public StringBuffer format(Date date, StringBuffer toAppendTo,
            FieldPosition fieldPosition) {
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
        String value = dateFormat.format(date);
        toAppendTo.append(value);
        return toAppendTo;
    }

    public Date parse(String source, ParsePosition pos) {
        pos.setIndex(source.length());
        return ISODateTimeFormat.dateTimeParser().parseDateTime(source).toDate();
    }

    public Object clone() {
        return this;
    }

    public String toString() {
        return this.getClass().getName();
    }
}

My test method:

  @Test
    public void testDateFormat() {
     df = new DefaultHttpClientUtil.ISO8601DateFormat();
     Date date = new Date();
     // df.setTimeZone(TimeZone.getTimeZone("GMT")); I'm getting NPE   
     // for this line

    assertThat(df.format(date)).isEqualTo(ISO8601Utils.format(date, 
    true));
  }

However, I am getting null pointer exception for the commented line. I assume it has to do with injecting or mocking object, but I am not sure how I should approach this problem.

Solution

ISO8601DateFormat and ISO8601Utils are deprecated since version 2.9 and do not provide clear documentation what to do after it was deprecated. There was a question on GitHub: ISO8601DateFormat is deprecated but replacement is unclear related to your question.

I guess, that someone from your team just used first class which he/she found to serialise Date to ISO8601 format and did not get to big attention that it comes from Jackson library. I recommend do not use internal *Utils classes from libraries you use for other reason. In that case for serialising/deserialising JSON. Right now, we have many options how to format dates and you should pick one for you. Mostly, it depends which JDK version do you use.

So, instead:

String value = ISO8601Utils.format(date, true);

Use for example SimpleDateFormat:

DateFormat df2 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");

As you can see below example prints the same date for both cases:

import com.fasterxml.jackson.databind.util.ISO8601Utils;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class JsonApp {

    public static void main(String[] args) throws Exception {
        Date date = new Date();
        DateFormat df2 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
        df2.setTimeZone(TimeZone.getTimeZone("GMT"));

        System.out.println(ISO8601Utils.format(date, true));
        System.out.println(df2.format(date));
    }
}

Above code prints:

2019-02-19T19:37:14.809Z
2019-02-19T19:37:14.809Z

Second parameter to ISO8601Utils.format is true which means that you need milliseconds in result and format should look like yyyy-MM-ddThh:mm:ss.sss'Z'.

For more info, read: