001// Copyright 2008 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.internal.util;
016
017import java.util.Locale;
018
019/**
020 * Contains code borrowed from <a href="http://commons.apache.org/lang/">commons-lang</a>.
021 */
022public class LocaleUtils
023{
024    /**
025     * <p>Converts a String to a Locale.</p> <p/> <p>This method takes the string format of a locale and creates the
026     * locale object from it.</p> <p/>
027     * <pre>
028     *   LocaleUtils.toLocale("en")         = new Locale("en", "")
029     *   LocaleUtils.toLocale("en_GB")      = new Locale("en", "GB")
030     *   LocaleUtils.toLocale("en_GB_xxx")  = new Locale("en", "GB", "xxx")   (#)
031     * </pre>
032     * <p/> <p>(#) The behaviour of the JDK variant constructor changed between JDK1.3 and JDK1.4. In JDK1.3, the
033     * constructor upper cases the variant, in JDK1.4, it doesn't. Thus, the result from getVariant() may vary depending
034     * on your JDK.</p> <p/> <p>This method validates the input strictly. The language code must be lowercase. The
035     * country code must be uppercase. The separator must be an underscore. The length must be correct. </p>
036     *
037     * @param input the locale String to convert, null returns null
038     * @return a Locale, null if null input
039     * @throws IllegalArgumentException if the string is an invalid format
040     */
041    public static Locale toLocale(String input)
042    {
043        if (input == null)
044            return null;
045
046        int len = input.length();
047        if (len != 2 && len != 5 && len < 7)
048            fail(input);
049
050        char ch0 = input.charAt(0);
051        char ch1 = input.charAt(1);
052
053        if (ch0 < 'a' || ch0 > 'z' || ch1 < 'a' || ch1 > 'z')
054            fail(input);
055
056        if (len == 2)
057            return new Locale(input, "");
058
059        if (input.charAt(2) != '_')
060            fail(input);
061
062        char ch3 = input.charAt(3);
063        if (ch3 == '_')
064            return new Locale(input.substring(0, 2), "", input.substring(4));
065
066        char ch4 = input.charAt(4);
067        if (ch3 < 'A' || ch3 > 'Z' || ch4 < 'A' || ch4 > 'Z')
068            fail(input);
069
070        if (len == 5)
071            return new Locale(input.substring(0, 2), input.substring(3, 5));
072
073        if (input.charAt(5) != '_')
074            fail(input);
075
076        return new Locale(input.substring(0, 2), input.substring(3, 5), input.substring(6));
077    }
078
079    private static void fail(String input)
080    {
081        throw new IllegalArgumentException(String.format("Unable to convert '%s' to a Locale instance.", input));
082    }
083
084}