DocumentBuilder builder = factory.newDocumentBuilder();
String validXml = ParserUtil.checkUnicodeString(page.getContent());
fel.getContext().set("$page_content", validXml);
Document doc = builder.parse(new ByteArrayInputStream(validXml.getBytes()));
XPathFactory xfactory = XPathFactoryImpl.newInstance();
XPath xpathParser = xfactory.newXPath();
//设置命名空间
xpathParser.setNamespaceContext(new NamespaceContext() {
public String getPrefix(String uri) {
throw new UnsupportedOperationException();
}