Java tutorial
/* * ==================================================================== * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package com.ccc.mail.mailinglist.utils; import java.lang.ref.SoftReference; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; import java.util.HashMap; import java.util.Locale; import java.util.Map; import java.util.TimeZone; import org.apache.http.annotation.Immutable; /** * A utility class for parsing and formatting HTTP dates as used in cookies and * other headers. This class handles dates as defined by RFC 2616 section * 3.3.1 as well as some other common non-standard formats. * * * @since 4.0 */ @Immutable public final class DateUtils { /** * Date format pattern used to parse HTTP date headers in RFC 1123 format. */ public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz"; /** * Date format pattern used to parse HTTP date headers in RFC 1036 format. */ public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz"; /** * Date format pattern used to parse HTTP date headers in ANSI C * <code>asctime()</code> format. */ public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy"; private static final String[] DEFAULT_PATTERNS = new String[] { PATTERN_RFC1036, PATTERN_RFC1123, PATTERN_ASCTIME }; private static final Date DEFAULT_TWO_DIGIT_YEAR_START; public static final TimeZone GMT = TimeZone.getTimeZone("GMT"); static { Calendar calendar = Calendar.getInstance(); calendar.setTimeZone(GMT); calendar.set(2000, Calendar.JANUARY, 1, 0, 0, 0); calendar.set(Calendar.MILLISECOND, 0); DEFAULT_TWO_DIGIT_YEAR_START = calendar.getTime(); } /** * Parses a date value. The formats used for parsing the date value are retrieved from * the default http params. * * @param dateValue the date value to parse * * @return the parsed date * * @throws DateParseException if the value could not be parsed using any of the * supported date formats */ public static Date parseDate(String dateValue) throws DateParseException { return parseDate(dateValue, null, null); } /** * Parses the date value using the given date formats. * * @param dateValue the date value to parse * @param dateFormats the date formats to use * * @return the parsed date * * @throws DateParseException if none of the dataFormats could parse the dateValue */ public static Date parseDate(final String dateValue, String[] dateFormats) throws DateParseException { return parseDate(dateValue, dateFormats, null); } /** * Parses the date value using the given date formats. * * @param dateValue the date value to parse * @param dateFormats the date formats to use * @param startDate During parsing, two digit years will be placed in the range * <code>startDate</code> to <code>startDate + 100 years</code>. This value may * be <code>null</code>. When <code>null</code> is given as a parameter, year * <code>2000</code> will be used. * * @return the parsed date * * @throws DateParseException if none of the dataFormats could parse the dateValue */ public static Date parseDate(String dateValue, String[] dateFormats, Date startDate) throws DateParseException { if (dateValue == null) { throw new IllegalArgumentException("dateValue is null"); } if (dateFormats == null) { dateFormats = DEFAULT_PATTERNS; } if (startDate == null) { startDate = DEFAULT_TWO_DIGIT_YEAR_START; } // trim single quotes around date if present // see issue #5279 if (dateValue.length() > 1 && dateValue.startsWith("'") && dateValue.endsWith("'")) { dateValue = dateValue.substring(1, dateValue.length() - 1); } for (String dateFormat : dateFormats) { SimpleDateFormat dateParser = DateFormatHolder.formatFor(dateFormat); dateParser.set2DigitYearStart(startDate); try { return dateParser.parse(dateValue); } catch (ParseException pe) { // ignore this exception, we will try the next format } } // we were unable to parse the date throw new DateParseException("Unable to parse the date " + dateValue); } /** * Formats the given date according to the RFC 1123 pattern. * * @param date The date to format. * @return An RFC 1123 formatted date string. * * @see #PATTERN_RFC1123 */ public static String formatDate(Date date) { return formatDate(date, PATTERN_RFC1123); } /** * Formats the given date according to the specified pattern. The pattern * must conform to that used by the {@link SimpleDateFormat simple date * format} class. * * @param date The date to format. * @param pattern The pattern to use for formatting the date. * @return A formatted date string. * * @throws IllegalArgumentException If the given date pattern is invalid. * * @see SimpleDateFormat */ public static String formatDate(Date date, String pattern) { if (date == null) throw new IllegalArgumentException("date is null"); if (pattern == null) throw new IllegalArgumentException("pattern is null"); SimpleDateFormat formatter = DateFormatHolder.formatFor(pattern); return formatter.format(date); } /** This class should not be instantiated. */ private DateUtils() { } /** * A factory for {@link SimpleDateFormat}s. The instances are stored in a * threadlocal way because SimpleDateFormat is not threadsafe as noted in * {@link SimpleDateFormat its javadoc}. * */ final static class DateFormatHolder { private static final ThreadLocal<SoftReference<Map<String, SimpleDateFormat>>> THREADLOCAL_FORMATS = new ThreadLocal<SoftReference<Map<String, SimpleDateFormat>>>() { @Override protected SoftReference<Map<String, SimpleDateFormat>> initialValue() { return new SoftReference<Map<String, SimpleDateFormat>>(new HashMap<String, SimpleDateFormat>()); } }; /** * creates a {@link SimpleDateFormat} for the requested format string. * * @param pattern * a non-<code>null</code> format String according to * {@link SimpleDateFormat}. The format is not checked against * <code>null</code> since all paths go through * {@link DateUtils}. * @return the requested format. This simple dateformat should not be used * to {@link SimpleDateFormat#applyPattern(String) apply} to a * different pattern. */ public static SimpleDateFormat formatFor(String pattern) { SoftReference<Map<String, SimpleDateFormat>> ref = THREADLOCAL_FORMATS.get(); Map<String, SimpleDateFormat> formats = ref.get(); if (formats == null) { formats = new HashMap<String, SimpleDateFormat>(); THREADLOCAL_FORMATS.set(new SoftReference<Map<String, SimpleDateFormat>>(formats)); } SimpleDateFormat format = formats.get(pattern); if (format == null) { format = new SimpleDateFormat(pattern, Locale.US); format.setTimeZone(TimeZone.getTimeZone("GMT")); formats.put(pattern, format); } return format; } } }