Note that this class saves dates with millisecond granularity, + * which is bad for {@link TermRangeQuery} and {@link PrefixQuery}, as those + * queries are expanded to a BooleanQuery with a potentially large number + * of terms when searching. Thus you might want to use + * {@link DateTools} instead. + * + *
+ * Note: dates before 1970 cannot be used, and therefore cannot be + * indexed when using this class. See {@link DateTools} for an + * alternative without such a limitation. + * + *
+ * Another approach is {@link NumericUtils}, which provides
+ * a sortable binary representation (prefix encoded) of numeric values, which
+ * date/time are.
+ * For indexing a {@link Date} or {@link Calendar}, just get the unix timestamp as
+ * long using {@link Date#getTime} or {@link Calendar#getTimeInMillis} and
+ * index this as a numeric value with {@link NumericField}
+ * and use {@link NumericRangeQuery} to query it.
+ *
+ * @deprecated If you build a new index, use {@link DateTools} or
+ * {@link NumericField} instead.
+ * This class is included for use with existing
+ * indices and will be removed in a future release (possibly Lucene 4.0).
+ */
+@Deprecated
+public class DateField {
+
+ private DateField() {}
+
+ // make date strings long enough to last a millenium
+ private static int DATE_LEN = Long.toString(1000L*365*24*60*60*1000,
+ Character.MAX_RADIX).length();
+
+ public static String MIN_DATE_STRING() {
+ return timeToString(0);
+ }
+
+ public static String MAX_DATE_STRING() {
+ char[] buffer = new char[DATE_LEN];
+ char c = Character.forDigit(Character.MAX_RADIX-1, Character.MAX_RADIX);
+ for (int i = 0 ; i < DATE_LEN; i++)
+ buffer[i] = c;
+ return new String(buffer);
+ }
+
+ /**
+ * Converts a Date to a string suitable for indexing.
+ * @throws RuntimeException if the date specified in the
+ * method argument is before 1970
+ */
+ public static String dateToString(Date date) {
+ return timeToString(date.getTime());
+ }
+ /**
+ * Converts a millisecond time to a string suitable for indexing.
+ * @throws RuntimeException if the time specified in the
+ * method argument is negative, that is, before 1970
+ */
+ public static String timeToString(long time) {
+ if (time < 0)
+ throw new RuntimeException("time '" + time + "' is too early, must be >= 0");
+
+ String s = Long.toString(time, Character.MAX_RADIX);
+
+ if (s.length() > DATE_LEN)
+ throw new RuntimeException("time '" + time + "' is too late, length of string " +
+ "representation must be <= " + DATE_LEN);
+
+ // Pad with leading zeros
+ if (s.length() < DATE_LEN) {
+ StringBuilder sb = new StringBuilder(s);
+ while (sb.length() < DATE_LEN)
+ sb.insert(0, 0);
+ s = sb.toString();
+ }
+
+ return s;
+ }
+
+ /** Converts a string-encoded date into a millisecond time. */
+ public static long stringToTime(String s) {
+ return Long.parseLong(s, Character.MAX_RADIX);
+ }
+ /** Converts a string-encoded date into a Date object. */
+ public static Date stringToDate(String s) {
+ return new Date(stringToTime(s));
+ }
+}