[FIXED] Correct java.time representation of XMLGregorianCalendar

Issue

I have a XML element with the following content:

<lastModified>2019-10-09T19:20:45.677+02:00</lastModified>

This is mapped to Java's XMLGregorianCalendar.

I need to convert this value in an appropriate java.time instance.

I am a little confused about which java.time class is the "correct" (i.e. lossless) representation of this XMLGregorianCalendar value.

I suppose it should be ZonedDateTime or is OffsetDateTime the better choice?

Solution

The String you have ("2019-10-09T19:20:45.677+02:00") is in an ISO format that doesn't even need an extra formatter in order to parse it. The main reason for the use of an OffsetDateTime are the last 6 characters: +02:00, which denote an offset of 2 hours from UTC (more than just one time zone may actually have this offset at the same time).

You can convert this value into the proper java.time instance like this, for example:

public static void main(String[] args) throws DatatypeConfigurationException {
    // your example datetime
    String lastModified = "2019-10-09T19:20:45.677+02:00";
    // create an XMLGregorianCalendar for example purpose
    XMLGregorianCalendar xmlGC = DatatypeFactory.newInstance()
                                                .newXMLGregorianCalendar(lastModified);
    // print it once in order to see the values
    System.out.println("XMLGregorianCalendar: " + xmlGC.toString());
    // parse its toString() method to an OffsetDateTime
    OffsetDateTime lastModOdt = OffsetDateTime.parse(xmlGC.toString());
    // format the content of the OffsetDateTime in ISO standard
    System.out.println("OffsetDateTime:       " 
            + lastModOdt.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME));
}

Output:

XMLGregorianCalendar: 2019-10-09T19:20:45.677+02:00
OffsetDateTime:       2019-10-09T19:20:45.677+02:00

This should be correct (lossless enough by losing no information).

Answered By - deHaar
Answer Checked By - Willingham (JavaFixing Volunteer)