Java如何提取完整的XML块

Question

使用此XML示例：

<A>
  <B>
    <id>0</id>
  </B>
  <B>
    <id>1</id>
  </B>
</A>

我想要一个简单的方法来提取节点B的XML块，并返回XML字符串：

<B>
  <id>1</id>
</B>

要检索此节点，我应该使用一些Java XPath库，例如XOM或Java XPath，但是我找不到如何获取完整的XML字符串。

Answer 1

添加到lwburk的解决方案中，要将DOM节点转换为字符串形式，可以使用Transformer：

private static String nodeToString(Node node)
throws TransformerException
{
    StringWriter buf = new StringWriter();
    Transformer xform = TransformerFactory.newInstance().newTransformer();
    xform.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
    xform.transform(new DOMSource(node), new StreamResult(buf));
    return(buf.toString());
}

完整的例子：

public static void main(String... args)
throws Exception
{
    String xml = "<A><B><id>0</id></B><B><id>1</id></B></A>";
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    Document doc = dbf.newDocumentBuilder().parse(new InputSource(new StringReader(xml)));

    XPath xPath = XPathFactory.newInstance().newXPath();
    Node result = (Node)xPath.evaluate("A/B[id = '1']", doc, XPathConstants.NODE);

    System.out.println(nodeToString(result));
}

private static String nodeToString(Node node)
throws TransformerException
{
    StringWriter buf = new StringWriter();
    Transformer xform = TransformerFactory.newInstance().newTransformer();
    xform.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
    xform.transform(new DOMSource(node), new StreamResult(buf));
    return(buf.toString());
}