JavaでXMLを作成する最適な手法とライブラリ活用｜DOM・JAXB・Jacksonの実装例を解説

import org.w3c.dom.Document;
import org.w3c.dom.Element;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import java.io.StringWriter;

public class DomXmlCreator {
    public static void main(String[] args) {
        try {
            // DocumentBuilderの生成
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
            Document doc = builder.newDocument();

            // ルート要素 <order> の作成
            Element rootElement = doc.createElement("order");
            rootElement.setAttribute("id", "ORD-1001");
            doc.appendChild(rootElement);

            // 子要素 <customer> の追加
            Element customer = doc.createElement("customer");
            customer.setTextContent("田中 太郎");
            rootElement.appendChild(customer);

            // 子要素 <item> の追加
            Element item = doc.createElement("item");
            Element itemName = doc.createElement("name");
            itemName.setTextContent("Javaプログラミング書籍");
            Element price = doc.createElement("price");
            price.setTextContent("3200");
            
            item.appendChild(itemName);
            item.appendChild(price);
            rootElement.appendChild(item);

            // Transformerを使用してXMLを文字列として出力
            TransformerFactory transformerFactory = TransformerFactory.newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            
            // インデント設定
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");

            StringWriter writer = new StringWriter();
            transformer.transform(new DOMSource(doc), new StreamResult(writer));

            // 結果の表示
            System.out.println(writer.toString());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<order id="ORD-1001">
    <customer>田中 太郎</customer>
    <item>
        <name>Javaプログラミング書籍</name>
        <price>3200</price>
    </item>
</order>

<dependency>
    <groupId>jakarta.xml.bind</groupId>
    <artifactId>jakarta.xml.bind-api</artifactId>
    <version>4.0.0</version>
</dependency>
<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>4.0.0</version>
    <scope>runtime</scope>
</dependency>

import jakarta.xml.bind.annotation.XmlAttribute;
import jakarta.xml.bind.annotation.XmlElement;
import jakarta.xml.bind.annotation.XmlRootElement;
import jakarta.xml.bind.JAXBContext;
import jakarta.xml.bind.Marshaller;
import java.io.StringWriter;

// ルート要素の定義
@XmlRootElement(name = "order")
class Order {
    private String id;
    private String customer;
    private Item item;

    @XmlAttribute // 属性として出力
    public String getId() { return id; }
    public void setId(String id) { this.id = id; }

    @XmlElement // 要素として出力
    public String getCustomer() { return customer; }
    public void setCustomer(String customer) { this.customer = customer; }

    @XmlElement
    public Item getItem() { return item; }
    public void setItem(Item item) { this.item = item; }
}

class Item {
    private String name;
    private int price;

    @XmlElement
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    @XmlElement
    public int getPrice() { return price; }
    public void setPrice(int price) { this.price = price; }
}

public class JaxbXmlCreator {
    public static void main(String[] args) {
        try {
            // データの準備
            Order order = new Order();
            order.setId("ORD-2002");
            order.setCustomer("佐藤 花子");
            
            Item item = new Item();
            item.setName("ワイヤレスマウス");
            item.setPrice(4500);
            order.setItem(item);

            // JAXBContextの初期化
            JAXBContext context = JAXBContext.newInstance(Order.class);
            Marshaller marshaller = context.createMarshaller();

            // フォーマット出力の設定
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);

            // XMLの出力
            StringWriter writer = new StringWriter();
            marshaller.marshal(order, writer);

            System.out.println(writer.toString());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<order id="ORD-2002">
    <customer>佐藤 花子</customer>
    <item>
        <name>ワイヤレスマウス</name>
        <price>4500</price>
    </item>
</order>

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
    <version>2.15.2</version>
</dependency>

import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
import com.fasterxml.jackson.databind.SerializationFeature;

@JacksonXmlRootElement(localName = "product")
class Product {
    @JacksonXmlProperty(isAttribute = true)
    private String code;
    
    @JacksonXmlProperty(localName = "productName")
    private String name;

    public Product(String code, String name) {
        this.code = code;
        this.name = name;
    }
    
    // Getter/Setterは省略
}

public class JacksonXmlCreator {
    public static void main(String[] args) {
        try {
            XmlMapper xmlMapper = new XmlMapper();
            // インデントを有効にする
            xmlMapper.enable(SerializationFeature.INDENT_OUTPUT);

            Product product = new Product("P-500", "ゲーミングキーボード");

            // オブジェクトをXML文字列に変換
            String xml = xmlMapper.writeValueAsString(product);
            
            System.out.println(xml);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

<product code="P-500">
  <productName>ゲーミングキーボード</productName>
</product>

@XmlRootElement(name = "order", namespace = "http://www.example.com/schema/order")

// ファイルへ直接書き込む例
marshaller.marshal(order, new File("output.xml"));