如何从XML文件解析数据创建Employee类对象数组

核心问题说明 #

你调用getAttributeValue()无法获取值的根本原因是你的XML结构中员工信息是*节点的子元素文本内容*，不是XML节点属性，只有形如<employee id="1" firstName="John">的属性写法才能通过属性相关方法获取值。

方案1：基于现有DOM代码改造 #

第一步：先定义Employee POJO类 #

public class Employee {
    private Integer id;
    private String firstName;
    private String lastName;
    private String country;
    private Integer age;

    // 无参构造、全参构造、getter方法自行补充
    public Employee() {}

    public void setId(Integer id) {
        this.id = id;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", firstName='" + firstName + '\'' +
                ", lastName='" + lastName + '\'' +
                ", country='" + country + '\'' +
                ", age=" + age +
                '}';
    }
}

第二步：修改DOM解析逻辑 #

DocumentBuilder documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document document = documentBuilder.parse("data.xml"); 
Node root = document.getDocumentElement(); 
NodeList staff = root.getChildNodes();
// 定义集合存储所有解析出的Employee对象
List<Employee> employeeList = new ArrayList<>();

for (int i = 0; i < staff.getLength(); i++) {
    Node employeeNode = staff.item(i);
    if (employeeNode.getNodeType() != Node.TEXT_NODE && "employee".equals(employeeNode.getNodeName())) {
        Employee employee = new Employee();
        NodeList employeeProps = employeeNode.getChildNodes();
        for (int j = 0; j < employeeProps.getLength(); j++) {
            Node propNode = employeeProps.item(j);
            if (propNode.getNodeType() != Node.TEXT_NODE) {
                String propName = propNode.getNodeName();
                String propValue = propNode.getTextContent().trim();
                // 按节点名称赋值给Employee对应字段
                switch (propName) {
                    case "id":
                        employee.setId(Integer.parseInt(propValue));
                        break;
                    case "firstName":
                        employee.setFirstName(propValue);
                        break;
                    case "lastName":
                        employee.setLastName(propValue);
                        break;
                    case "country":
                        employee.setCountry(propValue);
                        break;
                    case "age":
                        employee.setAge(Integer.parseInt(propValue));
                        break;
                }
            }
        }
        employeeList.add(employee);
    }
}
// 测试输出结果
employeeList.forEach(System.out::println);

方案2：更简便的JAXB实现（无需手动遍历DOM） #

JAXB是Java内置的XML绑定工具，可直接实现XML和Java对象的自动转换，代码更简洁：

第一步：给实体类加JAXB注解 #

import jakarta.xml.bind.annotation.XmlElement;
import jakarta.xml.bind.annotation.XmlRootElement;
// Java 8及更早版本使用javax.xml.bind.annotation包下的注解

@XmlRootElement(name = "employee")
public class Employee {
    private Integer id;
    private String firstName;
    private String lastName;
    private String country;
    private Integer age;

    @XmlElement
    public void setId(Integer id) {
        this.id = id;
    }

    @XmlElement
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    @XmlElement
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    @XmlElement
    public void setCountry(String country) {
        this.country = country;
    }

    @XmlElement
    public void setAge(Integer age) {
        this.age = age;
    }

    // 剩余getter、构造方法自行补充
}

// 定义根节点对应的Staff类
@XmlRootElement(name = "staff")
class Staff {
    private List<Employee> employees;

    @XmlElement(name = "employee")
    public void setEmployees(List<Employee> employees) {
        this.employees = employees;
    }

    public List<Employee> getEmployees() {
        return employees;
    }
}

第二步：直接解析XML文件 #

JAXBContext context = JAXBContext.newInstance(Staff.class);
Unmarshaller unmarshaller = context.createUnmarshaller();
Staff staff = (Staff) unmarshaller.unmarshal(new File("data.xml"));
List<Employee> employeeList = staff.getEmployees();
// 直接获取到所有解析完成的Employee对象

内容的提问来源于stack exchange，提问作者Viktor Loskutov