Java 在列表对象中存储具有相同标记的节点

我想将xml文件中具有相同标记的对象保存在一个列表中。例如，对于以下xml文件，每个员工都应该有一个

列表

属性，该属性将存储该员工的所有

值

<?xml version="1.0"?>
<Employees>
    <Employee>
        <name>Pankaj</name>
        <age>29</age>
        <age>42</age>
        <role>
            Java Developer
            Musician
            Artist
        </role>
        <gender>Male</gender>
    </Employee>
    <Employee>
        <name>Lisa</name>
        <age>35</age>
        <age>23</age>
        <role>CSS Developer</role>
        <gender>Female</gender>
    </Employee>
</Employees>

---

这是我第一次使用xml文件。你能帮我说说我做错了什么吗。提前感谢。

您从未初始化过

Employee.age

，因此它是

null

。可能与我初始化的Employee.age重复，并且NullPointerException已消失。但是，该程序只返回员工的第一个值，而不是您从未初始化的完整列表

Employee.age

，因此它是

null

。初始化的Employee.age和NullPointerException可能重复。但是，该程序仅返回员工的第一个值，而不是完整列表

import java.util.ArrayList;
import java.util.List;

public class Employee {
    private String name;
    private String gender;
    private List<Integer> age = new ArrayList<Integer>();
    private String role;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public List<Integer> getAge() {
        return this.age;
    }
    public void addAge(int age) {
        this.age.add(age);

    }
    public String getRole() {
        return role;
    }
    public void setRole(String role) {
        this.role = role;
    }

    @Override
    public String toString() {
        return "Employee:: Name=" + this.name +" Gender=" + this.gender +
                " Role=" + this.role;
    }

    public void agetoString() {
        for(Integer my_age : this.age) {
            System.out.println(my_age + " ");
        }
    }
}

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;


public class XMLReaderDOM {

    public static void main(String[] args) {
        String filePath = "employee.xml";
        File xmlFile = new File(filePath);
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder;
        try {
            dBuilder = dbFactory.newDocumentBuilder();
            Document doc = dBuilder.parse(xmlFile);
            doc.getDocumentElement().normalize();
            System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
            NodeList nodeList = doc.getElementsByTagName("Employee");
            //now XML is loaded as Document in memory, lets convert it to Object List
            List<Employee> empList = new ArrayList<Employee>();
            for (int i = 0; i < nodeList.getLength(); i++) {
                empList.add(getEmployee(nodeList.item(i)));
            }
            //lets print Employee list information
            for (Employee emp : empList) {
                System.out.println(emp.toString());
                emp.agetoString();
            }
        } catch (SAXException | ParserConfigurationException | IOException e1) {
            e1.printStackTrace();
        }

    }


    private static Employee getEmployee(Node node) {
        //XMLReaderDOM domReader = new XMLReaderDOM();
        Employee emp = new Employee();
        if (node.getNodeType() == Node.ELEMENT_NODE) {
            Element element = (Element) node;
            emp.setName(getTagValue("name", element));
            emp.addAge(Integer.parseInt(getTagValue("age", element)));
            emp.setGender(getTagValue("gender", element));
            emp.setRole(getTagValue("role", element));
        }

        return emp;
    }


    private static String getTagValue(String tag, Element element) {
        NodeList nodeList = element.getElementsByTagName(tag).item(0).getChildNodes();
        Node node = (Node) nodeList.item(0);
        return node.getNodeValue();
    }

}

Root element :Employees
Employee:: Name=Pankaj Gender=Male Role=
            Java Developer
            Musician
            Artist

29 
Employee:: Name=Lisa Gender=Female Role=CSS Developer
35