add xml decimal attribute escaper

guava/src/com/google/common/xml/XmlEscapers.java

@@ -98,9 +98,34 @@ public static Escaper xmlAttributeEscaper() {
  return XML_ATTRIBUTE_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 substitutes {@code 0xFFFD} for 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.
+ *
+ * <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 "&#9;"}, {@code "&#10;"}, and {@code "&#13;"}
+ * 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 xmlDecimalAttributeEscaper() {
+ return XML_DECIMAL_ATTRIBUTE_ESCAPER;
+ }
+
  private static final Escaper XML_ESCAPER;
  private static final Escaper XML_CONTENT_ESCAPER;
  private static final Escaper XML_ATTRIBUTE_ESCAPER;
+ private static final Escaper XML_DECIMAL_ATTRIBUTE_ESCAPER;
 
  static {
  Escapers.Builder builder = Escapers.builder();
@@ -139,5 +164,9 @@ public static Escaper xmlAttributeEscaper() {
  builder.addEscape('\n', "&#xA;");
  builder.addEscape('\r', "&#xD;");
  XML_ATTRIBUTE_ESCAPER = builder.build();
+ builder.addEscape('\t', "&#9;");
+ builder.addEscape('\n', "&#10;");
+ builder.addEscape('\r', "&#13;");
+ XML_DECIMAL_ATTRIBUTE_ESCAPER = builder.build();
  }
 }