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    
015    package org.apache.tapestry5.services;
016    
017    /**
018     * Service used to encode or decode strings that are placed into URLs.  This is used as an alternative to UUEncoding.
019     * Alphabetics, numbers and some punctuation ("-", "_", ".", ":") are passed through as is, the "$" character is an
020     * escape, followed by either another "$", or by a four digit hex unicode number.  A null input (not a blank input, but
021     * actual null) has a special encoding, "$N". Likewise, the blank string has the special encoding "$B".
022     */
023    public interface URLEncoder
024    {
025        /**
026         * Given an input value containing any characters, returns the input string, or an encoded version of the string (as
027         * outlined above).
028         *
029         * @param input string to be encoded, which may be null
030         * @return encoded version of input
031         */
032        String encode(String input);
033    
034        /**
035         * Given a previously encoded string, returns the original input.
036         *
037         * @param input encoded string (may not be null)
038         * @return decoded input
039         */
040        String decode(String input);
041    }