Java&Xml教程（四）使用DOM方式生成XML文件

在前面的教程中，我们学习了使用DOM解析方式读取和修改XML文件内容，今天我们来学习如何使用DOM解析机制生成XML文件。
下面是我们对要生成的XML文件的具体要求：
1.根节点元素为”Employees”,命名空间为”http://www.journaldev.com/employee“,根节点下包含一系列的Employee元素。
2.员工的信息通过Employee节点表示，生成的XML文件有两条员工的信息。
3.每个员工有个”id”属性。
4.Employee 元素有四个子元素- “name”, “age”, “role”, “gender”。
下面是程序代码：

package com.journaldev.xml;import java.io.File;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.transform.OutputKeys;import javax.xml.transform.Transformer;import javax.xml.transform.TransformerFactory;import javax.xml.transform.dom.DOMSource;import javax.xml.transform.stream.StreamResult;import org.w3c.dom.Document;import org.w3c.dom.Element;import org.w3c.dom.Node;public class XMLWriterDOM {    public static void main(String[] args) {        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();        DocumentBuilder dBuilder;        try {            dBuilder = dbFactory.newDocumentBuilder();            Document doc = dBuilder.newDocument();            //add elements to Document            Element rootElement =                doc.createElementNS("http://www.journaldev.com/employee", "Employees");            //append root element to document            doc.appendChild(rootElement);            //append first child element to root element            rootElement.appendChild(getEmployee(doc, "1", "Pankaj", "29", "Java Developer", "Male"));            //append second child            rootElement.appendChild(getEmployee(doc, "2", "Lisa", "35", "Manager", "Female"));            //for output to file, console            TransformerFactory transformerFactory = TransformerFactory.newInstance();            Transformer transformer = transformerFactory.newTransformer();            //for pretty print            transformer.setOutputProperty(OutputKeys.INDENT, "yes");            DOMSource source = new DOMSource(doc);            //write to console or file            StreamResult console = new StreamResult(System.out);            StreamResult file = new StreamResult(new File("/Users/pankaj/emps.xml"));            //write data            transformer.transform(source, console);            transformer.transform(source, file);            System.out.println("DONE");        } catch (Exception e) {            e.printStackTrace();        }    }    private static Node getEmployee(Document doc, String id, String name, String age, String role,            String gender) {        Element employee = doc.createElement("Employee");        //set id attribute        employee.setAttribute("id", id);        //create name element        employee.appendChild(getEmployeeElements(doc, employee, "name", name));        //create age element        employee.appendChild(getEmployeeElements(doc, employee, "age", age));        //create role element        employee.appendChild(getEmployeeElements(doc, employee, "role", role));        //create gender element        employee.appendChild(getEmployeeElements(doc, employee, "gender", gender));        return employee;    }    //utility method to create text node    private static Node getEmployeeElements(Document doc, Element element, String name, String value) {        Element node = doc.createElement(name);        node.appendChild(doc.createTextNode(value));        return node;    }}

需要注意的是代码中创建了两个StreamResult对象，一个是出于调试的目的將XML文件内容输出到控制台中，另一个將XML内容写到文件中。
程序输出的XML内容：

<?xml version="1.0" encoding="UTF-8" standalone="no"?><Employees xmlns="http://www.journaldev.com/employee"><Employee id="1"><name>Pankaj</name><age>29</age><role>Java Developer</role><gender>Male</gender></Employee><Employee id="2"><name>Lisa</name><age>35</age><role>Manager</role><gender>Female</gender></Employee></Employees>

该XML内容没有格式化，如果你需要对XML内容做适当的格式化，参考这篇文章Java中格式化XML