D-Net

package eu.dnetlib.openaire.common;

import java.text.FieldPosition;

import java.util.*;

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

public class RFC3339DateFormat extends StdDateFormat {

	private static final TimeZone TIMEZONE_Z = TimeZone.getTimeZone("UTC");

	// Same as ISO8601DateFormat but serializing milliseconds.

	@Override

	public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {

		String value = format(date, true, TIMEZONE_Z, Locale.US);

		toAppendTo.append(value);

		return toAppendTo;

	}

	/**

	 * Format date into yyyy-MM-ddThh:mm:ss[.sss][Z|[+-]hh:mm]

	 *

	 * @param date   the date to format

	 * @param millis true to include millis precision otherwise false

	 * @param tz     timezone to use for the formatting (UTC will produce 'Z')

	 * @return the date formatted as yyyy-MM-ddThh:mm:ss[.sss][Z|[+-]hh:mm]

	 */

	private static String format(Date date, boolean millis, TimeZone tz, Locale loc) {

		Calendar calendar = new GregorianCalendar(tz, loc);

		calendar.setTime(date);

		// estimate capacity of buffer as close as we can (yeah, that's pedantic ;)

		StringBuilder sb = new StringBuilder(30);

		sb.append(String.format(

				"%04d-%02d-%02dT%02d:%02d:%02d",

				calendar.get(Calendar.YEAR),

				calendar.get(Calendar.MONTH) + 1,

				calendar.get(Calendar.DAY_OF_MONTH),

				calendar.get(Calendar.HOUR_OF_DAY),

				calendar.get(Calendar.MINUTE),

				calendar.get(Calendar.SECOND)

		));

		if (millis) {

			sb.append(String.format(".%03d", calendar.get(Calendar.MILLISECOND)));

		}

		int offset = tz.getOffset(calendar.getTimeInMillis());

		if (offset != 0) {

			int hours = Math.abs((offset / (60 * 1000)) / 60);

			int minutes = Math.abs((offset / (60 * 1000)) % 60);

			sb.append(String.format("%c%02d:%02d",

					(offset < 0 ? '-' : '+'),

					hours, minutes));

		} else {

			sb.append('Z');

		}

		return sb.toString();

	}

}