Question

我有一个像这样的XML文件：

<list>
<job>
    <id>B001</id>
    <name>前処理</name>
    <time>7</time>
    <status>success</status>
</job>
<job>
    <id>B002</id>
    <name>商品データ・商品分類関連データDB取込</name>
    <time>1</time>
    <status>success</status>
</job>

我试图使用DomParser将id = B002的作业时间更改为3.这里我的代码：

public boolean changeTimeOfJob(String id, String time) {
    try {

        ClassLoader classLoader = getClass().getClassLoader();
        File inputFile = new File(classLoader.getResource("batch/" + "jobManagement.xml").getFile());
        DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
        Document doc = docBuilder.parse(inputFile);
        Node jobs = doc.getFirstChild();

        NodeList childNodes = jobs.getChildNodes();

        for (int count = 0; count < childNodes.getLength(); count++) {
            Node job = childNodes.item(count);
            System.out.println(job.toString());
            if (job.getFirstChild().getTextContent().equals(id)) {
                NodeList list = job.getChildNodes();
                for (int temp = 0; temp < list.getLength(); temp++) {
                    Node node = list.item(temp);
                    if (node.getNodeType() == Node.ELEMENT_NODE) {
                        Element eElement = (Element) node;
                        if (eElement.getNodeName().equals("time")) {
                            eElement.setTextContent(time);
                        }
                    }
                }
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

我在这一行job.getFirstChild().getTextContent().equals(id)得到了一个NullPointerException，但我不知道为什么？谁知道更好的方法？

现在我正在尝试使用此代码：

        Element docEle = doc.getDocumentElement();
        NodeList nl = docEle.getChildNodes();
        if (nl != null) {
            int length = nl.getLength();
            for (int i = 0; i < length; i++) {
                if (nl.item(i).getNodeType() == Node.ELEMENT_NODE) {
                    Element el = (Element) nl.item(i);
                    if (el.getElementsByTagName("id").item(0).getTextContent().equals(id)) {
                        el.getElementsByTagName("time").item(0).setTextContent(time);
                        System.out.println(el.getElementsByTagName("id").item(0).getTextContent());
                        System.out.println(el.getElementsByTagName("time").item(0).getTextContent());
                    }
                }
            }
        }

但是setTextContent（）方法不起作用

Answer 1

使用XPath：

    String id = "B002";
    String time = "3";

    XPath xp = XPathFactory.newInstance().newXPath();
    String expr = String.format("/list/job[id = '%s']/time/text()", id);
    Text textNode = (Text) xp.evaluate(expr, doc, XPathConstants.NODE);
    textNode.setNodeValue(time);

更新：完成示例，根据需要调整加载并保存documnet。

public class Main {

static String XML = "<list>\n" + 
        "<job>\n" + 
        "    <id>B001</id>\n" + 
        "    <name>前処理</name>\n" + 
        "    <time>7</time>\n" + 
        "    <status>success</status>\n" + 
        "</job>\n" + 
        "<job>\n" + 
        "    <id>B002</id>\n" + 
        "    <name>商品データ・商品分類関連データDB取込</name>\n" + 
        "    <time>1</time>\n" + 
        "    <status>success</status>\n" + 
        "</job>\n" + "</list>";

static Document readDocument() throws Exception {
    DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
    f.setNamespaceAware(true);
    Document doc = f.newDocumentBuilder()
            .parse(new InputSource(new ByteArrayInputStream(XML.getBytes(StandardCharsets.UTF_8))));
    return doc;
}

static void changeTimeOfJob(Document doc, String id, String time) throws Exception {
    XPath xp = XPathFactory.newInstance().newXPath();
    String expr = String.format("/list/job[id = '%s']/time/text()", id);
    Text textNode = (Text) xp.evaluate(expr, doc, XPathConstants.NODE);
    textNode.setNodeValue(time);
}

static void saveDocuemnt(Document doc, OutputStream out) throws Exception {
    DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
    f.setNamespaceAware(true);
    DOMImplementationLS impl = (DOMImplementationLS) f.newDocumentBuilder().getDOMImplementation();
    LSOutput output = impl.createLSOutput();
    output.setByteStream(out);
    LSSerializer ser = impl.createLSSerializer();
    ser.write(doc, output);
}

public static void main(String[] args) throws Exception {
    Document doc = readDocument();
    changeTimeOfJob(doc, "B002", "3");
    saveDocuemnt(doc, System.out);
}

}

使用DomParser修改XML

1 个答案: