StringEscapeUtils.unescapeXml(str) does not support supplemental characters.

StringEscapeUtils.unescapeXml(str) does not unescape numeric character references of supplemental characters:

String str2 = StringEscapeUtils.unescapeXml("𣎴");
System.out.println(str2.codePointAt(0));
//38 (it means '&'.)

This output should be 144308.

Currently, StringEscapeUtils.unescapeXml(StringEscapeUtils.escapeXml(str)) is equal to str, so it doesn't seem to be wrong. But, as we reported in LANG-728, StringEscapeUtils.escapeXml(str) has a bug. When the bug is fixed, StringEscapeUtils.unescapeXml(StringEscapeUtils.escapeXml(str)) would not be equal to str. We do not expect it. (Of course, we don't expect that StringEscapeUtils.unescapeXml(StringEscapeUtils.escapeXml(str)) is always equal to str.)