/*
* Copyright (c) 2010 Google Inc.
*
* 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.
*/
package com.google.api.client.escape;
/**
* An object that converts literal text into a format safe for inclusion in a
* particular context (such as an XML document). Typically (but not always), the
* inverse process of "unescaping" the text is performed automatically by the
* relevant parser.
*
* <p>
* For example, an XML escaper would convert the literal string {@code
* "Foo<Bar>"} into {@code "Foo<Bar>"} to prevent {@code "<Bar>"} from
* being confused with an XML tag. When the resulting XML document is parsed,
* the parser API will return this text as the original literal string {@code
* "Foo<Bar>"}.
*
* <p>
* An {@code Escaper} instance is required to be stateless, and safe when used
* concurrently by multiple threads.
*
* <p>
* Several popular escapers are defined as constants in the class
* {@link CharEscapers}.
*
* @since 2.2
*/
public abstract class Escaper {
/**
* Returns the escaped form of a given literal string.
*
* <p>
* Note that this method may treat input characters differently depending on
* the specific escaper implementation.
* <ul>
* <li>{@link UnicodeEscaper} handles <a
* href="http://en.wikipedia.org/wiki/UTF-16">UTF-16</a> correctly, including
* surrogate character pairs. If the input is badly formed the escaper should
* throw {@link IllegalArgumentException}.
* </ul>
*
* @param string the literal string to be escaped
* @return the escaped form of {@code string}
* @throws NullPointerException if {@code string} is null
* @throws IllegalArgumentException if {@code string} contains badly formed
* UTF-16 or cannot be escaped for any other reason
*/
public abstract String escape(String string);
}