EaglerForge/sources/main/java/com/google/common/xml/XmlEscapers.java

158 lines
6.2 KiB
Java

/*
* 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.xml;
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 XML
* attribute values and elements' text contents. When possible, avoid manual
* escaping by using templating systems and high-level APIs that provide
* autoescaping. For example, consider <a href="http://www.xom.nu/">XOM</a> or
* <a href="http://www.jdom.org/">JDOM</a>.
*
* <p>
* <b>Note</b>: Currently the escapers provided by this class do not escape any
* characters outside the ASCII character range. Unlike HTML escaping the XML
* escapers will not escape non-ASCII characters to their numeric entity
* replacements. These XML escapers provide the minimal level of escaping to
* ensure that the output can be safely included in a Unicode XML document.
*
*
* <p>
* For details on the behavior of the escapers in this class, see sections
* <a href="http://www.w3.org/TR/2008/REC-xml-20081126/#charsets">2.2</a> and
* <a href="http://www.w3.org/TR/2008/REC-xml-20081126/#syntax">2.4</a> of the
* XML specification.
*
* @author Alex Matevossian
* @author David Beaumont
* @since 15.0
*/
@Beta
@GwtCompatible
public class XmlEscapers {
private XmlEscapers() {
}
private static final char MIN_ASCII_CONTROL_CHAR = 0x00;
private static final char MAX_ASCII_CONTROL_CHAR = 0x1F;
// For each xxxEscaper() method, please add links to external reference pages
// that are considered authoritative for the behavior of that escaper.
// TODO(user): When this escaper strips \uFFFE & \uFFFF, add this doc.
// <p>This escaper also silently removes non-whitespace control characters and
// the character values {@code 0xFFFE} and {@code 0xFFFF} which are not
// permitted in XML. For more detail see section
// <a href="http://www.w3.org/TR/2008/REC-xml-20081126/#charsets">2.2</a> of
// the XML specification.
/**
* Returns an {@link Escaper} instance that escapes special characters in a
* string so it can safely be included in an XML document as element content.
* See section
* <a href="http://www.w3.org/TR/2008/REC-xml-20081126/#syntax">2.4</a> of the
* XML specification.
*
* <p>
* <b>Note</b>: Double and single quotes are not escaped, so it is <b>not
* safe</b> to use this escaper to escape attribute values. Use
* {@link #xmlContentEscaper} if the output can appear in element content or
* {@link #xmlAttributeEscaper} in attribute values.
*
* <p>
* This escaper does not escape non-ASCII characters to their numeric character
* references (NCR). Any non-ASCII characters appearing in the input will be
* preserved in the output. Specifically "\r" (carriage return) is preserved in
* the output, which may result in it being silently converted to "\n" when the
* XML is parsed.
*
* <p>
* This escaper does not treat surrogate pairs specially and does not perform
* Unicode validation on its input.
*/
public static Escaper xmlContentEscaper() {
return XML_CONTENT_ESCAPER;
}
/**
* Returns an {@link Escaper} instance that escapes special characters in a
* string so it can safely be included in XML document as an attribute value.
* See section
* <a href="http://www.w3.org/TR/2008/REC-xml-20081126/#AVNormalize">3.3.3</a>
* of the XML specification.
*
* <p>
* This escaper does not escape non-ASCII characters to their numeric character
* references (NCR). However, horizontal tab {@code '\t'}, line feed
* {@code '\n'} and carriage return {@code '\r'} are escaped to a corresponding
* NCR {@code "&#x9;"}, {@code "&#xA;"}, and {@code "&#xD;"} respectively. Any
* other non-ASCII characters appearing in the input will be preserved in the
* output.
*
* <p>
* This escaper does not treat surrogate pairs specially and does not perform
* Unicode validation on its input.
*/
public static Escaper xmlAttributeEscaper() {
return XML_ATTRIBUTE_ESCAPER;
}
private static final Escaper XML_ESCAPER;
private static final Escaper XML_CONTENT_ESCAPER;
private static final Escaper XML_ATTRIBUTE_ESCAPER;
static {
Escapers.Builder builder = Escapers.builder();
// The char values \uFFFE and \uFFFF are explicitly not allowed in XML
// (Unicode code points above \uFFFF are represented via surrogate pairs
// which means they are treated as pairs of safe characters).
// TODO(user): When refactoring done change the \uFFFF below to \uFFFD
builder.setSafeRange(Character.MIN_VALUE, '\uFFFF');
// Unsafe characters are removed.
builder.setUnsafeReplacement("");
// Except for '\n', '\t' and '\r' we remove all ASCII control characters.
// An alternative to this would be to make a map that simply replaces the
// allowed ASCII whitespace characters with themselves and set the minimum
// safe character to 0x20. However this would slow down the escaping of
// simple strings that contain '\t','\n' or '\r'.
for (char c = MIN_ASCII_CONTROL_CHAR; c <= MAX_ASCII_CONTROL_CHAR; c++) {
if (c != '\t' && c != '\n' && c != '\r') {
builder.addEscape(c, "");
}
}
// Build the content escaper first and then add quote escaping for the
// general escaper.
builder.addEscape('&', "&amp;");
builder.addEscape('<', "&lt;");
builder.addEscape('>', "&gt;");
XML_CONTENT_ESCAPER = builder.build();
builder.addEscape('\'', "&apos;");
builder.addEscape('"', "&quot;");
XML_ESCAPER = builder.build();
builder.addEscape('\t', "&#x9;");
builder.addEscape('\n', "&#xA;");
builder.addEscape('\r', "&#xD;");
XML_ATTRIBUTE_ESCAPER = builder.build();
}
}