/*
* Copyright (C) 2009 The Guava Authors
*
* 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.common.html;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.escape.Escaper;
import com.google.common.escape.Escapers;
/**
* {@code Escaper} instances suitable for strings to be included in HTML
* attribute values and <em>most</em> elements' text contents. When possible,
* avoid manual escaping by using templating systems and high-level APIs that
* provide autoescaping.
*
* <p>HTML escaping is particularly tricky: For example, <a
* href="http://goo.gl/5TgZb">some elements' text contents must not be HTML
* escaped</a>. As a result, it is impossible to escape an HTML document
* correctly without domain-specific knowledge beyond what {@code HtmlEscapers}
* provides. We strongly encourage the use of HTML templating systems.
*
* @author Sven Mawson
* @author David Beaumont
* @since 15.0
*/
@Beta
@GwtCompatible
public final class HtmlEscapers {
/**
* Returns an {@link Escaper} instance that escapes HTML metacharacters as
* specified by <a href="http://www.w3.org/TR/html4/">HTML 4.01</a>. The
* resulting strings can be used both in attribute values and in <em>most</em>
* elements' text contents, provided that the HTML document's character
* encoding can encode any non-ASCII code points in the input (as UTF-8 and
* other Unicode encodings can).
*
*
* <p><b>Note:</b> This escaper only performs minimal escaping to make content
* structurally compatible with HTML. Specifically, it does not perform entity
* replacement (symbolic or numeric), so it does not replace non-ASCII code
* points with character references. This escaper escapes only the following
* five ASCII characters: {@code '"&<>}.
*/
public static Escaper htmlEscaper() {
return HTML_ESCAPER;
}
// For each xxxEscaper() method, please add links to external reference pages
// that are considered authoritative for the behavior of that escaper.
private static final Escaper HTML_ESCAPER =
Escapers.builder()
.addEscape('"', """)
// Note: "'" is not defined in HTML 4.01.
.addEscape('\'', "'")
.addEscape('&', "&")
.addEscape('<', "<")
.addEscape('>', ">")
.build();
private HtmlEscapers() {}
}