选择性 XML 读取

Question

我能够按照下面的代码读取XML。

这是一个示例输入文件：

<explain>
    <Query-Text>
    </Query-Text>
    <Plan>
        <Node-Type></Node-Type>
        <Startup-Cost></Startup-Cost>
        <Total-Cost></Total-Cost>
        <Actual-Total-Time></Actual-Total-Time>
        <Actual-Rows></Actual-Rows>
        <Actual-Loops></Actual-Loops>
        <Plans>
                <Plan>
                        <Node-Type></Node-Type>
                        <Startup-Cost></Startup-Cost>
                        <Total-Cost></Total-Cost>
                        <Actual-Rows></Actual-Rows>
                        <Actual-Loops></Actual-Loops>
                </Plan>
          </Plans>
    </Plan>
</explain>

我只需要读取标签PLAN: "Total-Cost"并从第一个PLAN标签中"Actual-Total-Time"信息。问题是内部层次结构中存在PLAN，这也正在被读取。我怎么能只阅读第一个PLAN标签，而不阅读里面我不感兴趣的标签？这是我的代码：

File fXmlFile = new File("/home/user1/Downloads/LOGT1.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);
doc.getDocumentElement().normalize();
System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("Plan");
for (int temp = 0; temp < nList.getLength(); temp++) {
    //SAMPLE Node nNode = nList.item(temp);
    System.out.println("nCurrent Element :" + nNode.getNodeName());                            
    if (nNode.getNodeType() == Node.ELEMENT_NODE) {             Element eElement = (Element) nNode;
        System.out.println("Total Cost query: " + eElement.getElementsByTagName("Total-Cost").item(0).getTextContent());
        System.out.println("Actual Total Time query:" + eElement.getElementsByTagName("Actual-Total-Time").item(0).getTextContent());
        }

此代码不会引发任何错误，但它不遵循所需的行为。

Answer 1

我想你正在寻找这样的东西：

for (int temp = 0; temp < nList.getLength(); temp++) { //SAMPLE       
    Node nNode = nList.item(temp);
    if (nNode.getParent().getNodeName().equals("Plans")) {
        continue;
    }
    System.out.println("nCurrent Element :" + nNode.getNodeName());
    ...
}

Answer 2

只需使用 XPath 即可获取值。下面的代码会给你你想要的：

XPath xPath = XPathFactory.newInstance().newXPath();
String Total_Cost = xPath.evaluate("//explain/Plan/Total-Cost/text()", doc).trim();
String Actual_Total_Time = xPath.evaluate("//explain/Plan/Actual-Total-Time/text()", doc).trim();