<!-- JAXB 核心依賴 -->
<dependency>
    <groupId>jakarta.xml.bind</groupId>
    <artifactId>jakarta.xml.bind-api</artifactId>
    <version>2.3.3</version>
</dependency>
<!-- 運行時實現(xiàn)（必須，否則報錯 ClassNotFoundException） -->
<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>2.3.3</version>
    <scope>runtime</scope>
</dependency>
<!-- 用于 JDK 9+ 模塊支持（可選，解決模塊訪問限制） -->
<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-core</artifactId>
    <version>2.3.3</version>
</dependency>

implementation 'jakarta.xml.bind:jakarta.xml.bind-api:2.3.3'
runtimeOnly 'com.sun.xml.bind:jaxb-impl:2.3.3'
runtimeOnly 'com.sun.xml.bind:jaxb-core:2.3.3'

import javax.xml.bind.annotation.*;
import java.util.List;

// 根元素：XML 根節(jié)點名為 <user>
@XmlRootElement(name = "user")
// 訪問策略：直接操作字段（無需 getter/setter，簡化代碼）
@XmlAccessorType(XmlAccessType.FIELD)
public class User {

    // XML 元素的屬性：<user id="1001">
    @XmlAttribute(name = "id")
    private Long userId;

    // XML 子元素：<username>張三</username>（必選）
    @XmlElement(name = "username", required = true)
    private String name;

    // XML 子元素：<age>25</age>
    @XmlElement
    private Integer age;

    // 嵌套對象（XML 子元素嵌套）
    @XmlElement(name = "address")
    private Address address;

    // 集合字段（XML 子元素：<hobbies>籃球 足球</hobbies>）
    @XmlElement(name = "hobbies")
    @XmlList // 集合元素序列化為單個元素的多個值
    private List<String> hobbies;

    // 忽略該字段（不生成 XML 元素）
    @XmlTransient
    private String password;

    // 嵌套類（地址信息）
    @XmlAccessorType(XmlAccessType.FIELD)
    public static class Address {
        @XmlElement(name = "province")
        private String province;
        @XmlElement(name = "city")
        private String city;

        // 必須有默認無參構(gòu)造器（JAXB 反射創(chuàng)建對象時需要）
        public Address() {}
        public Address(String province, String city) {
            this.province = province;
            this.city = city;
        }

        // getter/setter（可選，因使用 FIELD 訪問策略）
        // ...
    }

    // 必須有默認無參構(gòu)造器（JAXB 強制要求）
    public User() {}

    // 帶參構(gòu)造器（方便創(chuàng)建對象）
    public User(Long userId, String name, Integer age, Address address, List<String> hobbies) {
        this.userId = userId;
        this.name = name;
        this.age = age;
        this.address = address;
        this.hobbies = hobbies;
    }

    // getter/setter（可選，若需外部操作字段）
    // ...
}

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.File;
import java.io.StringWriter;
import java.util.Arrays;

public class JaxbMarshallerDemo {
    public static void main(String[] args) {
        // 1. 創(chuàng)建 Java 對象（模擬數(shù)據(jù)）
        User.Address address = new User.Address("廣東省", "深圳市");
        User user = new User(
            1001L,
            "張三",
            25,
            address,
            Arrays.asList("籃球", "足球", "編程")
        );

        try {
            // 2. 創(chuàng)建 JAXBContext（參數(shù)為要綁定的實體類）
            JAXBContext context = JAXBContext.newInstance(User.class);

            // 3. 獲取 Marshaller 實例（負責(zé)序列化）
            Marshaller marshaller = context.createMarshaller();

            // 4. 配置 Marshaller
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); // 格式化輸出（換行、縮進）
            marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8"); // 編碼格式
            marshaller.setProperty(Marshaller.JAXB_FRAGMENT, false); // 是否省略 XML 聲明（<?xml ...?>）

            // 5. 序列化到 XML 文件
            File xmlFile = new File("user.xml");
            marshaller.marshal(user, xmlFile);
            System.out.println("XML 文件已生成：" + xmlFile.getAbsolutePath());

            // 6. 序列化到字符串（便于網(wǎng)絡(luò)傳輸?shù)葓鼍埃?
            StringWriter writer = new StringWriter();
            marshaller.marshal(user, writer);
            String xmlStr = writer.toString();
            System.out.println("\nXML 字符串：");
            System.out.println(xmlStr);

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

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<user id="1001">
    <username>張三</username>
    <age>25</age>
    <address>
        <province>廣東省</province>
        <city>深圳市</city>
    </address>
    <hobbies>籃球 足球 編程</hobbies>
</user>

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import java.io.File;
import java.io.StringReader;

public class JaxbUnmarshallerDemo {
    public static void main(String[] args) {
        try {
            // 1. 創(chuàng)建 JAXBContext
            JAXBContext context = JAXBContext.newInstance(User.class);

            // 2. 獲取 Unmarshaller 實例（負責(zé)反序列化）
            Unmarshaller unmarshaller = context.createUnmarshaller();

            // 3. 從 XML 文件反序列化到對象
            File xmlFile = new File("user.xml");
            User userFromFile = (User) unmarshaller.unmarshal(xmlFile);
            System.out.println("從文件解析的 User：");
            System.out.println("用戶ID：" + userFromFile.getUserId());
            System.out.println("姓名：" + userFromFile.getName());
            System.out.println("地址：" + userFromFile.getAddress().getProvince() + "-" + userFromFile.getAddress().getCity());
            System.out.println("愛好：" + userFromFile.getHobbies());

            // 4. 從 XML 字符串反序列化到對象
            String xmlStr = """
                <?xml version="1.0" encoding="UTF-8"?>
                <user id="1002">
                    <username>李四</username>
                    <age>30</age>
                    <address>
                        <province>浙江省</province>
                        <city>杭州市</city>
                    </address>
                    <hobbies>讀書 旅行</hobbies>
                </user>
                """;
            StringReader reader = new StringReader(xmlStr);
            User userFromStr = (User) unmarshaller.unmarshal(reader);
            System.out.println("\n從字符串解析的 User：");
            System.out.println("用戶ID：" + userFromStr.getUserId());
            System.out.println("姓名：" + userFromStr.getName());

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

@XmlRootElement(name = "users")
@XmlAccessorType(XmlAccessType.FIELD)
public class UserList {
    @XmlElement(name = "user") // 每個 User 對應(yīng) <user> 子元素
    private List<User> userList;

    public UserList() {}
    public UserList(List<User> userList) {
        this.userList = userList;
    }

    // getter/setter
}

List<User> users = Arrays.asList(user1, user2);
UserList userList = new UserList(users);
marshaller.marshal(userList, new File("users.xml"));

<users>
    <user id="1001">...</user>
    <user id="1002">...</user>
</users>

import javax.xml.bind.annotation.adapters.XmlAdapter;
import java.text.SimpleDateFormat;
import java.util.Date;

// 適配 Date <-> String（自定義格式）
public class DateAdapter extends XmlAdapter<String, Date> {
    private static final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    @Override
    public Date unmarshal(String xmlStr) throws Exception {
        return sdf.parse(xmlStr);
    }

    @Override
    public String marshal(Date date) throws Exception {
        return sdf.format(date);
    }
}

@XmlElement(name = "createTime")
@XmlJavaTypeAdapter(DateAdapter.class) // 應(yīng)用適配器
private Date createTime;

<createTime>2025-11-25 14:30:00</createTime>

// JAXB 2.2+ 支持，需引入 jaxb-impl 依賴
marshaller.setProperty("com.sun.xml.bind.marshaller.NullPolicy", NullPolicy.SKIP);

@XmlElement(nillable = false)
private Integer age;