使用jaxb：http://www.mkyong.com/java/jaxb-hello-world-example/

package com.mkyong.core;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Customer {

    String name;
    int age;
    int id;

    public String getName() {
        return name;
    }

    @XmlElement
    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

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

    public int getId() {
        return id;
    }

    @XmlAttribute
    public void setId(int id) {
        this.id = id;
    }

}

package com.mkyong.core;

import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;

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

      Customer customer = new Customer();
      customer.setId(100);
      customer.setName("mkyong");
      customer.setAge(29);

      try {

        File file = new File("C:\\file.xml");
        JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);
        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();

        // output pretty printed
        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        jaxbMarshaller.marshal(customer, file);
        jaxbMarshaller.marshal(customer, System.out);

      } catch (JAXBException e) {
        e.printStackTrace();
      }

    }
}

public static void main(String[] args) {

try {

    DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
    Document doc = docBuilder.newDocument();
    Element rootElement = doc.createElement("CONFIGURATION");
    doc.appendChild(rootElement);
    Element browser = doc.createElement("BROWSER");
    browser.appendChild(doc.createTextNode("chrome"));
    rootElement.appendChild(browser);
    Element base = doc.createElement("BASE");
    base.appendChild(doc.createTextNode("http:fut"));
    rootElement.appendChild(base);
    Element employee = doc.createElement("EMPLOYEE");
    rootElement.appendChild(employee);
    Element empName = doc.createElement("EMP_NAME");
    empName.appendChild(doc.createTextNode("Anhorn, Irene"));
    employee.appendChild(empName);
    Element actDate = doc.createElement("ACT_DATE");
    actDate.appendChild(doc.createTextNode("20131201"));
    employee.appendChild(actDate);
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    DOMSource source = new DOMSource(doc);
    StreamResult result = new StreamResult(new File("/Users/myXml/ScoreDetail.xml"));
    transformer.transform(source, result);
    System.out.println("File saved!");
  } catch (ParserConfigurationException pce) {
    pce.printStackTrace();
  } catch (TransformerException tfe) {
    tfe.printStackTrace();}}

xml中的值是硬编码的。

您可以在java中使用jdom库。将标记定义为元素对象，用document类记录元素，用saxbuilder构建xml文件。请尝试以下示例：

//Root Element
Element root=new Element("CONFIGURATION");
Document doc=new Document();
//Element 1
Element child1=new Element("BROWSER");
//Element 1 Content
child1.addContent("chrome");
//Element 2
Element child2=new Element("BASE");
//Element 2 Content
child2.addContent("http:fut");
//Element 3
Element child3=new Element("EMPLOYEE");
//Element 3 --> In this case this element has another element with Content
child3.addContent(new Element("EMP_NAME").addContent("Anhorn, Irene"));

//Add it in the root Element
root.addContent(child1);
root.addContent(child2);
root.addContent(child3);
//Define root element like root
doc.setRootElement(root);
//Create the XML
XMLOutputter outter=new XMLOutputter();
outter.setFormat(Format.getPrettyFormat());
outter.output(doc, new FileWriter(new File("myxml.xml")));

不需要任何外部库，jre系统库提供您所需要的一切。
我推断你有一个 org.w3c.dom.Document 要写入文件的对象
要做到这一点，你需要一个 javax.xml.transform.Transformer :

import org.w3c.dom.Document
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.dom.DOMSource; 
import javax.xml.transform.stream.StreamResult; 

public class XMLWriter {
    public static void writeDocumentToFile(Document document, File file) {

        // Make a transformer factory to create the Transformer
        TransformerFactory tFactory = TransformerFactory.newInstance();

        // Make the Transformer
        Transformer transformer = tFactory.newTransformer();

        // Mark the document as a DOM (XML) source
        DOMSource source = new DOMSource(document);

        // Say where we want the XML to go
        StreamResult result = new StreamResult(file);

        // Write the XML to file
        transformer.transform(source, result);
    }
}

资料来源：http://docs.oracle.com/javaee/1.4/tutorial/doc/jaxpxslt4.html