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Tomcat example source code file (FastHttpDateFormat.java)

This example Tomcat source code file (FastHttpDateFormat.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

cache_size, concurrenthashmap, concurrenthashmap, date, dateformat, eee, hh:mm:ss, long, long, mmm, simpledateformat, simpledateformat, string, string, text, threading, threads, util

The Tomcat FastHttpDateFormat.java source code

/*
 *  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.
 */

package org.apache.tomcat.util.http;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Utility class to generate HTTP dates.
 * 
 * @author Remy Maucherat
 */
public final class FastHttpDateFormat {


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


    protected static final int CACHE_SIZE = 
        Integer.parseInt(System.getProperty("org.apache.tomcat.util.http.FastHttpDateFormat.CACHE_SIZE", "1000"));

    
    /**
     * HTTP date format.
     */
    protected static final SimpleDateFormat format = 
        new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US);


    /**
     * The set of SimpleDateFormat formats to use in getDateHeader().
     */
    protected static final SimpleDateFormat formats[] = {
        new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US),
        new SimpleDateFormat("EEEEEE, dd-MMM-yy HH:mm:ss zzz", Locale.US),
        new SimpleDateFormat("EEE MMMM d HH:mm:ss yyyy", Locale.US)
    };


    protected final static TimeZone gmtZone = TimeZone.getTimeZone("GMT");


    /**
     * GMT timezone - all HTTP dates are on GMT
     */
    static {

        format.setTimeZone(gmtZone);

        formats[0].setTimeZone(gmtZone);
        formats[1].setTimeZone(gmtZone);
        formats[2].setTimeZone(gmtZone);

    }


    /**
     * Instant on which the currentDate object was generated.
     */
    protected static long currentDateGenerated = 0L;


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


    /**
     * Formatter cache.
     */
    protected static final ConcurrentHashMap<Long, String> formatCache = 
        new ConcurrentHashMap<Long, String>(CACHE_SIZE);


    /**
     * Parser cache.
     */
    protected static final ConcurrentHashMap<String, Long> parseCache = 
        new ConcurrentHashMap<String, Long>(CACHE_SIZE);


    // --------------------------------------------------------- Public Methods


    /**
     * Get the current date in HTTP format.
     */
    public static final String getCurrentDate() {

        long now = System.currentTimeMillis();
        if ((now - currentDateGenerated) > 1000) {
            synchronized (format) {
                if ((now - currentDateGenerated) > 1000) {
                    currentDateGenerated = now;
                    currentDate = format.format(new Date(now));
                }
            }
        }
        return currentDate;

    }


    /**
     * Get the HTTP format of the specified date.
     */
    public static final String formatDate
        (long value, DateFormat threadLocalformat) {

        Long longValue = new Long(value);
        String cachedDate = formatCache.get(longValue);
        if (cachedDate != null)
            return cachedDate;

        String newDate = null;
        Date dateValue = new Date(value);
        if (threadLocalformat != null) {
            newDate = threadLocalformat.format(dateValue);
            updateFormatCache(longValue, newDate);
        } else {
            synchronized (formatCache) {
                synchronized (format) {
                    newDate = format.format(dateValue);
                }
                updateFormatCache(longValue, newDate);
            }
        }
        return newDate;

    }


    /**
     * Try to parse the given date as a HTTP date.
     */
    public static final long parseDate(String value, 
                                       DateFormat[] threadLocalformats) {

        Long cachedDate = parseCache.get(value);
        if (cachedDate != null)
            return cachedDate.longValue();

        Long date = null;
        if (threadLocalformats != null) {
            date = internalParseDate(value, threadLocalformats);
            updateParseCache(value, date);
        } else {
            synchronized (parseCache) {
                date = internalParseDate(value, formats);
                updateParseCache(value, date);
            }
        }
        if (date == null) {
            return (-1L);
        } else {
            return date.longValue();
        }

    }


    /**
     * Parse date with given formatters.
     */
    private static final Long internalParseDate
        (String value, DateFormat[] formats) {
        Date date = null;
        for (int i = 0; (date == null) && (i < formats.length); i++) {
            try {
                date = formats[i].parse(value);
            } catch (ParseException e) {
                ;
            }
        }
        if (date == null) {
            return null;
        }
        return new Long(date.getTime());
    }


    /**
     * Update cache.
     */
    private static void updateFormatCache(Long key, String value) {
        if (value == null) {
            return;
        }
        if (formatCache.size() > CACHE_SIZE) {
            formatCache.clear();
        }
        formatCache.put(key, value);
    }


    /**
     * Update cache.
     */
    private static void updateParseCache(String key, Long value) {
        if (value == null) {
            return;
        }
        if (parseCache.size() > CACHE_SIZE) {
            parseCache.clear();
        }
        parseCache.put(key, value);
    }


}

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