How do I parse RFC 3339 datetimes with Java?

Question

I'm trying to parse the date returned as a value from the HTML5 datetime input field. Try it in Opera to see an example. The date returned looks like this: 2011-05-03T11:58:01Z.

I'd like to parse that into a Java Date or Calendar Object.

Ideally a solution should have the following things:

• No external libraries (jars)
• Handles all acceptable RFC 3339 formats
• A String should be able to be easily validated to see if it is a valid RFC 3339 date

Answer 1

Just found that google implemented Rfc3339 parser in Google HTTP Client Library

https://github.com/google/google-http-java-client/blob/dev/google-http-client/src/main/java/com/google/api/client/util/DateTime.java

Tested. It works well to parse varies sub seconds time fragment.

import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.Date;

import com.google.api.client.util.DateTime;

DateTimeFormatter formatter = DateTimeFormatter
            .ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
            .withZone(ZoneId.of("UTC"));

@Test
public void test1e9Parse() {
    String timeStr = "2018-04-03T11:32:26.553955473Z";

    DateTime dateTime = DateTime.parseRfc3339(timeStr);
    long millis = dateTime.getValue();

    String result = formatter.format(new Date(millis).toInstant());

    assert result.equals("2018-04-03T11:32:26.553Z");
}

@Test
public void test1e3Parse() {
    String timeStr = "2018-04-03T11:32:26.553Z";

    DateTime dateTime = DateTime.parseRfc3339(timeStr);
    long millis = dateTime.getValue();

    String result = formatter.format(new Date(millis).toInstant());

    assert result.equals("2018-04-03T11:32:26.553Z");
}

@Test
public void testEpochSecondsParse() {

    String timeStr = "2018-04-03T11:32:26Z";

    DateTime dateTime = DateTime.parseRfc3339(timeStr);
    long millis = dateTime.getValue();

    String result = formatter.format(new Date(millis).toInstant());

    assert result.equals("2018-04-03T11:32:26.000Z");
}