/*
* 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.util.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 1.0
*/
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);
}