Đọc file XML

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package xulyxml;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

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

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

public class Main {
    public static void main(String[] args) {

        try {
            FileInputStream file = new FileInputStream(new File("employees.xml"));

            DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

            DocumentBuilder builder =  builderFactory.newDocumentBuilder();

            Document xmlDocument = builder.parse(file);

            XPath xPath =  XPathFactory.newInstance().newXPath();

            System.out.println("*************************");
            String expression = "/Employees/Employee[@emplid='1111']/email";
            System.out.println(expression);
            String email = xPath.compile(expression).evaluate(xmlDocument);
            System.out.println(email);

            System.out.println("*************************");
            expression = "/Employees/Employee/firstname";
            System.out.println(expression);
            NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
            for (int i = 0; i < nodeList.getLength(); i++) {
                System.out.println(nodeList.item(i).getFirstChild().getNodeValue());
            }

            System.out.println("*************************");
            expression = "/Employees/Employee[@type='admin']/firstname";
            System.out.println(expression);
            nodeList = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
            for (int i = 0; i < nodeList.getLength(); i++) {
                System.out.println(nodeList.item(i).getFirstChild().getNodeValue());
            }

            System.out.println("*************************");
            expression = "/Employees/Employee[@emplid='2222']";
            System.out.println(expression);
            Node node = (Node) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODE);
            if(null != node) {
                nodeList = node.getChildNodes();
                for (int i = 0;null!=nodeList && i < nodeList.getLength(); i++) {
                    Node nod = nodeList.item(i);
                    if(nod.getNodeType() == Node.ELEMENT_NODE)
                        System.out.println(nodeList.item(i).getNodeName() + " : " + nod.getFirstChild().getNodeValue());
                }
            }

            System.out.println("*************************");

            expression = "/Employees/Employee[age>40]/firstname";
            nodeList = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
            System.out.println(expression);
            for (int i = 0; i < nodeList.getLength(); i++) {
                System.out.println(nodeList.item(i).getFirstChild().getNodeValue());
            }

            System.out.println("*************************");
            expression = "/Employees/Employee[1]/firstname";
            System.out.println(expression);
            nodeList = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
            for (int i = 0; i < nodeList.getLength(); i++) {
                System.out.println(nodeList.item(i).getFirstChild().getNodeValue());
            }
            System.out.println("*************************");
            expression = "/Employees/Employee[position() <= 2]/firstname";
            System.out.println(expression);
            nodeList = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
            for (int i = 0; i < nodeList.getLength(); i++) {
                System.out.println(nodeList.item(i).getFirstChild().getNodeValue());
            }

            System.out.println("*************************");
            expression = "/Employees/Employee[last()]/firstname";
            System.out.println(expression);
            nodeList = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
            for (int i = 0; i < nodeList.getLength(); i++) {
                System.out.println(nodeList.item(i).getFirstChild().getNodeValue());
            }

            System.out.println("*************************");

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }
    }
}