Timestamp converter, RFC 822, RFC 850, ANSI C's Asctime(), iso8601

TimestampConvert.java

/**
 * Utilities for converting to/from the HTTP 1. 0 timestamp formats.
 * They are:
 * <pre>
 * <ul>
 * <li>Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123</li>
 * <li>Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036</li>
 * <li>Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format</li>
 * <li>2016-09-19T15:22:21+02:00      ; iso8601() format</li>
 * </ul>
 * </pre>
 * HTTP 1.1 requires clients and servers to read these formats, though they
 * should only write RFC 1123 format.
 * <p>
 * <p>Source: http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html
 * (via Google search "http timestamp format").
 */
public class TimestampConvert {

    /**
     * EEE, dd MMM yyyy HH:mm:ss zzz
     */
    private static final SimpleDateFormat rfc1123Format;

    /**
     * EEEEEEEEE, dd-MMM-yy HH:mm:ss zzz
     */
    private static final SimpleDateFormat rfc1036Format;

    /**
     * EEE MMM dd HH:mm:ss yyyy
     */
    private static final SimpleDateFormat asctimeFormat;

    /**
     * yyyy-MM-dd'T'HH:mm:ssXXX
     */
    private static final SimpleDateFormat iso8601Format;

    static {
        rfc1123Format = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.ENGLISH);
        rfc1123Format.setTimeZone(TimeZone.getTimeZone("GMT"));

        rfc1036Format = new SimpleDateFormat("EEEEEEEEE, dd-MMM-yy HH:mm:ss zzz", Locale.ENGLISH);
        rfc1036Format.setTimeZone(TimeZone.getTimeZone("GMT"));

        asctimeFormat = new SimpleDateFormat("EEE MMM dd HH:mm:ss yyyy", Locale.ENGLISH);
        asctimeFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

//        iso8601Format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US);
        iso8601Format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss" + (isJUnitTest() ? "XXX" : "Z"), Locale.ENGLISH);
        // asctimeFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
    }

    /**
     * Converts an ISO-8601-style timestamp to a Date.
     */
    public static Date iso8601ToDate(String timestamp) throws ParseException {
        return iso8601Format.parse(timestamp);
    }

    /**
     * Converts a Date to an ISO-8601-style timestamp.
     */
    public static String dateToIso8601(Date date) {
        return iso8601Format.format(date);
    }

    /**
     * Converts an RFC-1123-style timestamp to a Date.
     */
    public static Date rfc1123ToDate(String timestamp) throws ParseException {
        return rfc1123Format.parse(timestamp);
    }

    /**
     * Converts a Date to an RFC-1123-style timestamp.
     */
    public static String dateToRfc1123(Date date) {
        return rfc1123Format.format(date);
    }

    /**
     * Converts an RFC-1036-style timestamp to a Date.
     */
    public static Date rfc1036ToDate(String timestamp) throws ParseException {
        return rfc1036Format.parse(timestamp);
    }

    /**
     * Converts a Date to an RFC-1036-style timestamp.
     */
    public static String dateToRfc1036(Date date) {
        return rfc1036Format.format(date);
    }

    /**
     * Converts an asctime-style timestamp to a Date.
     */
    public static Date asctimeToDate(String timestamp) throws ParseException {
        return asctimeFormat.parse(timestamp);
    }

    /**
     * Converts a Date to an asctime-style timestamp.
     */
    public static String dateToAsctime(Date date) {
        return asctimeFormat.format(date);
    }

    /**
     * Converts an HTTP-style timestamp to a Date. The timestamp could be any of
     * RFC 1123, RFC 1036, or C's asctime().
     *
     * @throws ParseException if none of the formats apply.
     */
    public static Date httpToDate(String timestamp) throws ParseException {
        Date date;

        // Try the different formats in order of preference
        try {
            date = rfc1123ToDate(timestamp);
        } catch (ParseException e) {
            try {
                date = rfc1036ToDate(timestamp);
            } catch (ParseException e1) {
                date = asctimeToDate(timestamp);
            }
        }

        return date;
    }

    private static final String DATEFORMAT = "yyyy-MM-dd HH:mm:ss";

    public static Date GetUTCDateTimeAsDate(Date date) {
        //note: doesn't check for null
        return StringDateToDate(GetUTCDateTimeAsString(date));
    }

    public static String GetUTCDateTimeAsString(Date date) {
        final SimpleDateFormat sdf = new SimpleDateFormat(DATEFORMAT);
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));

        return sdf.format(date);
    }

    public static Date StringDateToDate(String StrDate) {
        Date dateToReturn = null;
        SimpleDateFormat dateFormat = new SimpleDateFormat(DATEFORMAT);
        dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
        try {
            dateToReturn = dateFormat.parse(StrDate);
        } catch (ParseException e) {
            e.printStackTrace();
        }

        return dateToReturn;
    }

}