001package org.apache.maven.scm.util;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 * http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import java.lang.ref.SoftReference;
023import java.text.DateFormat;
024import java.text.FieldPosition;
025import java.text.ParsePosition;
026import java.text.SimpleDateFormat;
027import java.util.Date;
028
029/**
030 * Thread-safe version of java.text.DateFormat.
031 * You can declare it as a static final variable:
032 * @author Olivier Lamy
033 * <code>
034 * private static final ThreadSafeDateFormat DATE_FORMAT = new ThreadSafeDateFormat( DATE_PATTERN );
035 * </code>
036 */
037public class ThreadSafeDateFormat
038    extends DateFormat
039{
040    private static final long serialVersionUID = 3786090697869963812L;
041
042    private final String dateFormat;
043
044    public ThreadSafeDateFormat( String sDateFormat )
045    {
046        dateFormat = sDateFormat;
047    }
048
049    private final ThreadLocal<SoftReference<SimpleDateFormat>> formatCache =
050        new ThreadLocal<SoftReference<SimpleDateFormat>>()
051    {
052        public SoftReference<SimpleDateFormat> get()
053        {
054            SoftReference<SimpleDateFormat> softRef = super.get();
055            if ( softRef == null || softRef.get() == null )
056            {
057                softRef = new SoftReference<SimpleDateFormat>( new SimpleDateFormat( dateFormat ) );
058                super.set( softRef );
059            }
060            return softRef;
061        }
062    };
063
064    private DateFormat getDateFormat()
065    {
066        return formatCache.get().get();
067    }
068
069    public StringBuffer format( Date date, StringBuffer toAppendTo, FieldPosition fieldPosition )
070    {
071        return getDateFormat().format( date, toAppendTo, fieldPosition );
072    }
073
074    public Date parse( String source, ParsePosition pos )
075    {
076        return getDateFormat().parse( source, pos );
077    }
078}