Class FastHttpDateFormat

java/org/apache/tomcat/util/http/FastHttpDateFormat.java:29–189

Utility class to generate HTTP dates.

 * Utility class to generate HTTP dates.
 */
public final class FastHttpDateFormat {

    /**
     * Private constructor to prevent instantiation. This is a utility class with only static methods.
     */
    private FastHttpDateFormat() {
    }


    // -------------------------------------------------------------- Variables


    private static final int CACHE_SIZE =
            Integer.getInteger("org.apache.tomcat.util.http.FastHttpDateFormat.CACHE_SIZE", 1000).intValue();


    // HTTP date formats
    private static final String DATE_RFC5322 = "EEE, dd MMM yyyy HH:mm:ss z";
    private static final String DATE_OBSOLETE_RFC850 = "EEEEEE, dd-MMM-yy HH:mm:ss zzz";
    private static final String DATE_OBSOLETE_ASCTIME = "EEE MMMM d HH:mm:ss yyyy";

    private static final ConcurrentDateFormat FORMAT_RFC5322;
    private static final ConcurrentDateFormat FORMAT_OBSOLETE_RFC850;
    private static final ConcurrentDateFormat FORMAT_OBSOLETE_ASCTIME;

    private static final ConcurrentDateFormat[] httpParseFormats;

    static {
        // All the formats that use a timezone use GMT
        TimeZone tz = TimeZone.getTimeZone("GMT");

        FORMAT_RFC5322 = new ConcurrentDateFormat(DATE_RFC5322, Locale.US, tz);
        FORMAT_OBSOLETE_RFC850 = new ConcurrentDateFormat(DATE_OBSOLETE_RFC850, Locale.US, tz);
        FORMAT_OBSOLETE_ASCTIME = new ConcurrentDateFormat(DATE_OBSOLETE_ASCTIME, Locale.US, tz);

        httpParseFormats =
                new ConcurrentDateFormat[] { FORMAT_RFC5322, FORMAT_OBSOLETE_RFC850, FORMAT_OBSOLETE_ASCTIME };
    }

    /**
     * Instant on which the currentDate object was generated.
     */
    private static volatile long currentDateGeneratedInSeconds = 0L;


    /**
     * Current formatted date.
     */
    private static String currentDate = null;


    /**
     * Formatter cache.
     * <p>
     * Note: This needs to be a ConcurrentHashMap for correct operation so declare it as such (rather than as Map).
     */
    private static final ConcurrentHashMap<Long,String> formatCache = new ConcurrentHashMap<>(CACHE_SIZE);