com.box.boxjavalibv2.utils.ISO8601DateParser.java Source code

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Here is the source code for com.box.boxjavalibv2.utils.ISO8601DateParser.java

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package com.box.boxjavalibv2.utils;

/*
 * Copyright 1999,2004 The Apache Software Foundation. Licensed 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.
 */

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

import org.apache.commons.lang3.StringUtils;

/**
 * ISO 8601 date parsing utility. Designed for parsing the ISO subset used in Dublin Core, RSS 1.0, and Atom.
 * 
 * @author <a href="mailto:burton@apache.org">Kevin A. Burton (burtonator)</a>
 * @version $Id: ISO8601DateParser.java,v 1.2 2005/06/03 20:25:29 snoopdave Exp $
 */
public class ISO8601DateParser {

    // Use ThreadLocal because SimpleDateFormat is not thread safe. See http://www.javacodegeeks.com/2010/07/java-best-practices-dateformat-in.html.
    private final static ThreadLocal<DateFormat> mThreadLocalSimpleDateFormat = new ThreadLocal<DateFormat>() {

        @Override
        protected DateFormat initialValue() {
            return new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssz");
        }

    };

    // 2004-06-14T19:GMT20:30Z
    // 2004-06-20T06:GMT22:01Z

    // http://www.cl.cam.ac.uk/~mgk25/iso-time.html
    //
    // http://www.intertwingly.net/wiki/pie/DateTime
    //
    // http://www.w3.org/TR/NOTE-datetime
    //
    // Different standards may need different levels of granularity in the date and
    // time, so this profile defines six levels. Standards that reference this
    // profile should specify one or more of these granularities. If a given
    // standard allows more than one granularity, it should specify the meaning of
    // the dates and times with reduced precision, for example, the result of
    // comparing two dates with different precisions.

    // The formats are as follows. Exactly the components shown here must be
    // present, with exactly this punctuation. Note that the "T" appears literally
    // in the string, to indicate the beginning of the time element, as specified in
    // ISO 8601.

    // Year:
    // YYYY (eg 1997)
    // Year and month:
    // YYYY-MM (eg 1997-07)
    // Complete date:
    // YYYY-MM-DD (eg 1997-07-16)
    // Complete date plus hours and minutes:
    // YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)
    // Complete date plus hours, minutes and seconds:
    // YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)
    // Complete date plus hours, minutes, seconds and a decimal fraction of a
    // second
    // YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)

    // where:

    // YYYY = four-digit year
    // MM = two-digit month (01=January, etc.)
    // DD = two-digit day of month (01 through 31)
    // hh = two digits of hour (00 through 23) (am/pm NOT allowed)
    // mm = two digits of minute (00 through 59)
    // ss = two digits of second (00 through 59)
    // s = one or more digits representing a decimal fraction of a second
    // TZD = time zone designator (Z or +hh:mm or -hh:mm)
    public static Date parse(String input) throws java.text.ParseException {

        // NOTE: SimpleDateFormat uses GMT[-+]hh:mm for the TZ which breaks
        // things a bit. Before we go on we have to repair this.
        DateFormat df = mThreadLocalSimpleDateFormat.get();

        // this is zero time so we need to add that TZ indicator for
        if (input.endsWith("Z")) {
            input = input.substring(0, input.length() - 1) + "GMT-00:00";
        } else {
            int inset = 6;

            String s0 = input.substring(0, input.length() - inset);
            String s1 = input.substring(input.length() - inset, input.length());

            input = s0 + "GMT" + s1;
        }

        return df.parse(input);

    }

    /**
     * Same as parse method but does not throws. In case input date string cannot be parsed, null is returned.
     */
    public static Date parseSilently(String input) {
        try {
            Date date = StringUtils.isEmpty(input) ? null : parse(input);
            return date;
        } catch (ParseException e) {
            return null;
        }
    }

    public static String toString(Date date) {

        DateFormat df = mThreadLocalSimpleDateFormat.get();

        TimeZone tz = TimeZone.getTimeZone("UTC");

        df.setTimeZone(tz);

        String output = df.format(date);

        String result = output.replaceAll("UTC", "+00:00");

        return result;

    }

}