使用DOM获取nodevalue的Java XML解析

Question

    try {
        String data = "<a><b c='d' e='f'>0.15</b></a>";
        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory
                .newInstance();
        DocumentBuilder documentBuilder = documentBuilderFactory
                .newDocumentBuilder();
        InputSource is = new InputSource();
        is.setCharacterStream(new StringReader(data));
        Document document = documentBuilder.parse(is);

        NodeList nl = document.getElementsByTagName("b");
        Node n = (Node) nl.item(0);
        System.out.println(n.getNodeValue());
    } catch (Exception e) {
        System.out.println("Exception " + e);

    }

我希望它打印0.15,但它打印为null.有任何想法吗？

编辑:这样做了

        if (n.hasChildNodes())
            System.out.println(n.getFirstChild().getNodeValue());
        else 
            System.out.println(n.getNodeValue());

Answer 1

那是因为一个元素实际上没有nodeValue.相反,它有一个文本节点作为孩子,它有nodeValue你想要的.

简而言之,您将希望getNodeValue()在元素节点的第一个子节点上.

有时元素包含多个文本节点,因为它们具有最大大小,在这种情况下,您需要从之前链接的页面中获取一些内容:

public static String getNodeValue(Node node) {
    StringBuffer buf = new StringBuffer();
    NodeList children = node.getChildNodes();
    for (int i = 0; i < children.getLength(); i++) {
        Node textChild = children.item(i);
        if (textChild.getNodeType() != Node.TEXT_NODE) {
            System.err.println("Mixed content! Skipping child element " + textChild.getNodeName());
            continue;
        }
        buf.append(textChild.getNodeValue());
    }
    return buf.toString();
}

Answer 2

尝试从Element而不是Node中提取它:

try {
    String data = "<a><b c='d' e='f'>0.15</b></a>";
    DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory
            .newInstance();
    DocumentBuilder documentBuilder = documentBuilderFactory
            .newDocumentBuilder();
    InputSource is = new InputSource();
    is.setCharacterStream(new StringReader(data));
    Document document = documentBuilder.parse(is);

    NodeList nl = document.getElementsByTagName("b");
    Element el = (Element) nl.item(0);
    Text elText = (Text) el.getFirstChild();
    String theValue = elText.getNodeValue();
    System.out.println(theValue);
} catch (Exception e) {
    System.out.println("Exception " + e);
}