在java中迭代XML的NodeList

Question

List<String> targetCollection = new ArrayList<>();
    try {
        XPath xPath = XPathFactory.newInstance().newXPath();
        if ( !namespaceContext.isEmpty() ) {
            xPath.setNamespaceContext(new MapNamespaceContext(namespaceContext));
        }
        XPathExpression expression = xPath.compile("Document");

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        factory.setNamespaceAware(!namespaceContext.isEmpty());
        Document document = factory.newDocumentBuilder().parse(new ByteArrayInputStream(source.getBytes(StandardCharsets.UTF_8)));

        NodeList nodeList = (NodeList) expression.evaluate(document, XPathConstants.NODESET);
        for (int i = 0; i < nodeList.getLength(); i++) {
            targetCollection.add(nodeToString(nodeList.item(i)));
        }
    }
    catch (SAXException | ParserConfigurationException | XPathExpressionException | IOException e) {
        throw new RuntimeException("Cannot split the specified message.");
    }

尝试使用上面的代码，但NOdeList为0 XML：

    <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Document xmlns="test:123:146">
    <A>
        <B>
        </B>
        <C>
            <D>
            <E></E>
            </D>
        </C>
    </A>
</Document>

（这是一个复杂的xml）调试节点列表为0，文档没有显示xml的所有节点 有什么建议我做错了吗？