httpdateformat.java

来自「resetful样式的ws样例,一种面向资源的webservices服务」· Java 代码 · 共 121 行

/*
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://jersey.dev.java.net/CDDL+GPL.html
 * or jersey/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at jersey/legal/LICENSE.txt.
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 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
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 * and therefore, elected the GPL Version 2 license, then the option applies
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 * holder.
 */

package com.sun.jersey.impl.http.header;

import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Helper class for HTTP specified date formats.
 *
 * @author [e-mail]
 */
public final class HttpDateFormat {
    
    private HttpDateFormat() {
    }
    
    /**
     * The date format pattern for RFC 1123.
     */
    private static final String RFC1123_DATE_FORMAT_PATTERN = "EEE, dd MMM yyyy HH:mm:ss zzz";
    
    /**
     * The date format pattern for RFC 1036.
     */
    private static final String RFC1036_DATE_FORMAT_PATTERN = "EEEE, dd-MMM-yy HH:mm:ss zzz";
    
    /**
     * The date format pattern for ANSI C asctime().
     */
    private static final String ANSI_C_ASCTIME_DATE_FORMAT_PATTERN = "EEE MMM d HH:mm:ss yyyy";
    
    private static ThreadLocal<List<SimpleDateFormat>> dateFormats = new ThreadLocal<List<SimpleDateFormat>>() {
        @Override
        protected synchronized List<SimpleDateFormat> initialValue() {
            return createDateFormats();
        }
    };
    
    private static List<SimpleDateFormat> createDateFormats() {
        SimpleDateFormat[] dateFormats = new SimpleDateFormat[] {
            new SimpleDateFormat(RFC1123_DATE_FORMAT_PATTERN, Locale.US),
            new SimpleDateFormat(RFC1036_DATE_FORMAT_PATTERN, Locale.US),
            new SimpleDateFormat(ANSI_C_ASCTIME_DATE_FORMAT_PATTERN, Locale.US)
        };
        
        TimeZone tz = TimeZone.getTimeZone("GMT");
        dateFormats[0].setTimeZone(tz);
        dateFormats[1].setTimeZone(tz);
        dateFormats[2].setTimeZone(tz);
        
        return Collections.unmodifiableList(Arrays.asList(dateFormats));
    }
    
    /**
     * Return an unmodifiable list of HTTP specified date formats to use for 
     * parsing or formating {@link Date}.
     * <p>
     * The list of date formats are scoped to the current thread and may be
     * used without requiring to synchronize access to the instances when 
     * parsing or formatting.
     *
     * @return the list of data formats.
     */
    public static List<SimpleDateFormat> getDateFormats() {
        return dateFormats.get();
    }

    /**
     * Get the preferred HTTP specified date format (RFC 1123).
     * <p>
     * The date format is scoped to the current thread and may be
     * used without requiring to synchronize access to the instance when 
     * parsing or formatting.
     *
     * @return the preferred of data format.
     */
    public static SimpleDateFormat getPreferedDateFormat() {
        return dateFormats.get().get(0);
    }
}