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Java XML 處理全棧實戰：DOM/DOM4J/XPath 生成與解析完整代碼

編輯：Java 相關知識

四大主流解析器定位

解析器	模型	特點	適用場景
DOM (W3C)	樹模型	全量加載內存、隨機訪問、可修改	小文件、需頻繁增刪改
SAX	事件流	流式、只讀、低內存	大文件、單次遍歷
JDOM	樹模型	Java 原生 API、輕量	中小文件、偏好原生風格
DOM4J	樹模型	功能最全、XPath、性能優、Hibernate/JAXM 採用	企業級首選

DOM 完整示例：生成 → 文件/字符串 → 解析

public class DomHandler {
    public String createXml() throws Exception {
        DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
        DocumentBuilder b = f.newDocumentBuilder();
        Document doc = b.newDocument();
        doc.setXmlVersion("1.0");

        Element root = doc.createElement("root");
        doc.appendChild(root);

        Element phone = doc.createElement("TelePhone");
        root.appendChild(phone);

        addType(doc, phone, "nokia", "599", "CMCC");
        addType(doc, phone, "xiaomi", "699", "ChinaNet");

        // 輸出字符串
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer t = tf.newTransformer();
        StringWriter sw = new StringWriter();
        t.transform(new DOMSource(doc), new StreamResult(sw));
        String xml = sw.toString();

        // 寫文件
        t.transform(new DOMSource(doc), new StreamResult(new File("phone.xml")));
        return xml;
    }

    private void addType(Document doc, Element parent, String name, String price, String op) {
        Element type = doc.createElement("type");
        type.setAttribute("name", name);
        Element p = doc.createElement("price"); p.setTextContent(price); type.appendChild(p);
        Element o = doc.createElement("operator"); o.setTextContent(op); type.appendChild(o);
        parent.appendChild(type);
    }

    public void parseXml(String xml) throws Exception {
        DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
        DocumentBuilder b = f.newDocumentBuilder();
        Document doc = b.parse(new InputSource(new StringReader(xml)));

        NodeList types = doc.getElementsByTagName("type");
        for (int i = 0; i < types.getLength(); i++) {
            Element e = (Element) types.item(i);
            System.out.println("Phone: " + e.getAttribute("name"));
            System.out.println("  Price: " + e.getElementsByTagName("price").item(0).getTextContent());
            System.out.println("  Operator: " + e.getElementsByTagName("operator").item(0).getTextContent());
        }
    }
}

DOM4J 示例：鏈式 API + XPath + 輸出格式化

public class Dom4jHandler {
    public String createXml() {
        Document doc = DocumentHelper.createDocument();
        Element root = doc.addElement("root");
        Element phone = root.addElement("TelePhone");

        addType(phone, "nokia", "599", "CMCC");
        addType(phone, "xiaomi", "699", "ChinaNet");

        // 格式化輸出字符串
        OutputFormat fmt = OutputFormat.createPrettyPrint();
        fmt.setEncoding("UTF-8");
        StringWriter sw = new StringWriter();
        new XMLWriter(sw, fmt).write(doc);
        return sw.toString();
    }

    private void addType(Element parent, String name, String price, String op) {
        Element type = parent.addElement("type").addAttribute("name", name);
        type.addElement("price").addText(price);
        type.addElement("operator").addText(op);
    }

    public void parseXml(String xml) throws DocumentException {
        SAXReader reader = new SAXReader();
        Document doc = reader.read(new InputSource(new StringReader(xml)));

        // 普通遍歷
        for (Element type : (List<Element>) doc.selectNodes("/root/TelePhone/type")) {
            System.out.println("Phone: " + type.attributeValue("name"));
            for (Element c : type.elements()) {
                System.out.println("  " + c.getName() + ": " + c.getText());
            }
        }
    }

    public void parseXmlByXPath(String xml) throws DocumentException {
        SAXReader reader = new SAXReader();
        Document doc = reader.read(new InputSource(new StringReader(xml)));

        // XPath 精準定位
        for (Element type : (List<Element>) doc.selectNodes("/root/TelePhone/type")) {
            System.out.println("Phone: " + type.attributeValue("name"));
            for (Element c : (List<Element>) type.selectNodes("./*")) {
                System.out.println("  " + c.getName() + ": " + c.getText());
            }
        }
    }
}

JDK 原生 XPath (無第三方依賴)

public class XpathHandler {
    public void parse(String xml) throws Exception {
        DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
        DocumentBuilder b = f.newDocumentBuilder();
        Document doc = b.parse(new InputSource(new StringReader(xml)));

        XPathFactory xf = XPathFactory.newInstance();
        XPath xpath = xf.newXPath();
        XPathExpression expr = xpath.compile("/root/TelePhone/type");
        NodeList types = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);

        for (int i = 0; i < types.getLength(); i++) {
            Element type = (Element) types.item(i);
            System.out.println("Phone: " + type.getAttribute("name"));
            NodeList props = (NodeList) xpath.compile("./*").evaluate(type, XPathConstants.NODESET);
            for (int j = 0; j < props.getLength(); j++) {
                Element p = (Element) props.item(j);
                System.out.println("  " + p.getTagName() + ": " + p.getTextContent());
            }
        }
    }
}

選型決策樹

文件 < 10MB、需修改、XPath 查詢 → **DOM4J**；
文件 > 100MB、單遍歷、只讀 → **SAX / StAX**；
零依賴、簡單查詢 → **JDK DOM + XPath**；
Android / 受限環境 → **JDK DOM / Pull Parser**。

依賴坐標 (Maven)

<dependency>
    <groupId>org.dom4j</groupId>
    <artifactId>dom4j</artifactId>
    <version>2.1.4</version>
</dependency>
<dependency>
    <groupId>jaxen</groupId> <!-- DOM4J XPath 依賴 -->
    <artifactId>jaxen</artifactId>
    <version>1.2.0</version>
</dependency>

掌握 DOM4J + XPath 組合，覆蓋 90% 企業級 XML 處理需求；理解 DOM/SAX/StAX 底層差異，面對極端場景游刃有餘。