Java HTML/XML - 如何使用XPath读取XML

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

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

public class Main {
  public static void main(String[] args) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setNamespaceAware(true);
    DocumentBuilder builder;
    Document doc = null;
    builder = factory.newDocumentBuilder();
    doc = builder.parse("employees.xml");
    // Create XPathFactory object
    XPathFactory xpathFactory = XPathFactory.newInstance();
    // Create XPath object
    XPath xpath = xpathFactory.newXPath();
    String name = getEmployeeNameById(doc, xpath, 4);
    System.out.println("Employee Name with ID 4: " + name);

    List<String> names = getEmployeeNameWithAge(doc, xpath, 30);
    System.out.println("Employees with 'age>30' are:"
        + Arrays.toString(names.toArray()));

    List<String> femaleEmps = getFemaleEmployeesName(doc, xpath);
    System.out.println("Female Employees names are:"
        + Arrays.toString(femaleEmps.toArray()));
  }
  private static List<String> getFemaleEmployeesName(Document doc, XPath xpath)
      throws Exception {
    List<String> list = new ArrayList<>();
    XPathExpression expr = xpath
        .compile("/Employees/Employee[gender='Female']/name/text()");
    // evaluate expression result on XML document
    NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
    for (int i = 0; i < nodes.getLength(); i++)
      list.add(nodes.item(i).getNodeValue());
    return list;
  }

  private static List<String> getEmployeeNameWithAge(Document doc, XPath xpath,
      int age) throws Exception {
    List<String> list = new ArrayList<>();
    XPathExpression expr = xpath.compile("/Employees/Employee[age>" + age
        + "]/name/text()");
    NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
    for (int i = 0; i < nodes.getLength(); i++)
      list.add(nodes.item(i).getNodeValue());
    return list;
  }

  private static String getEmployeeNameById(Document doc, XPath xpath, int id)
      throws Exception {
    String name = null;
    XPathExpression expr = xpath.compile("/Employees/Employee[@id='" + id
        + "']/name/text()");
    name = (String) expr.evaluate(doc, XPathConstants.STRING);
    return name;
  }

}