| /* |
| * 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 "	"}, {@code "
"}, and {@code "
"} |
| * 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('&', "&"); |
| builder.addEscape('<', "<"); |
| builder.addEscape('>', ">"); |
| XML_CONTENT_ESCAPER = builder.build(); |
| builder.addEscape('\'', "'"); |
| builder.addEscape('"', """); |
| XML_ESCAPER = builder.build(); |
| builder.addEscape('\t', "	"); |
| builder.addEscape('\n', "
"); |
| builder.addEscape('\r', "
"); |
| XML_ATTRIBUTE_ESCAPER = builder.build(); |
| } |
| } |