XStream - Annotations


XStream supports annotations similarly like automatic configuration instead of coding. In the previous chapter, we've seen the following configurations in code.

xstream.alias("student", Student.class);
xstream.alias("note", Note.class);

xstream.useAttributeFor(Student.class, "studentName");
xstream.aliasField("name", Student.class, "studentName");
xstream.addImplicitCollection(Student.class, "notes");

The following code snippet illustrates the use of annotations to do the same work in a much easier way.

@XStreamAlias("student")   //define class level alias
class Student {

   @XStreamAlias("name")   //define field level alias
   @XStreamAsAttribute     //define field as attribute
   private String studentName;
   @XStreamImplicit        //define list as an implicit collection
   private List<Note> notes = new ArrayList<Note>();
   @XStreamOmitField       //omit a field to not to be a part of XML
   private int type;

Let us test the above annotation using XStream.

Create a java class file named XStreamTester in C:\>XStream_WORKSPACE\com\tutorialspoint\xstream.

File: XStreamTester.java

package com.tutorialspoint.xstream;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

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

import javax.xml.transform.OutputKeys;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.stream.StreamResult;

import org.xml.sax.InputSource;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.annotations.XStreamImplicit;
import com.thoughtworks.xstream.annotations.XStreamOmitField;
import com.thoughtworks.xstream.io.xml.StaxDriver;

public class XStreamTester {

   public static void main(String args[]) {

      XStreamTester tester = new XStreamTester();
      XStream xstream = new XStream(new StaxDriver());
      Student student = tester.getStudentDetails();

      //Object to XML Conversion
      String xml = xstream.toXML(student);
   private Student getStudentDetails() {
      Student student = new Student("Mahesh");
      student.addNote(new Note("first","My first assignment."));
      student.addNote(new Note("second","My Second assignment."));
      return student;

   public static String formatXml(String xml) {
      try {
         Transformer serializer = SAXTransformerFactory.newInstance().newTransformer();
         serializer.setOutputProperty(OutputKeys.INDENT, "yes");
         serializer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
         Source xmlSource = new SAXSource(new InputSource(
            new ByteArrayInputStream(xml.getBytes())));
         StreamResult res = new StreamResult(new ByteArrayOutputStream());            
         serializer.transform(xmlSource, res);
         return new String(((ByteArrayOutputStream)res.getOutputStream()).toByteArray());
      } catch(Exception e) {
         return xml;

class Student {

   private String studentName;

   private List<Note> notes = new ArrayList<Note>();

   public Student(String name) {
      this.studentName = name;

   public void addNote(Note note) {

   public String getName() {
      return studentName;

   public List<Note> getNotes() {
      return notes;
   private int type;

   public int getType() {
      return type;

   public void setType(int type) {
      this.type = type;

class Note {
   private String title;
   private String description;

   public Note(String title, String description) {
      this.title = title;
      this.description = description;

   public String getTitle() {
      return title;

   public String getDescription() {
      return description;

Verify the Result

Compile the classes using javac compiler as follows −

C:\XStream_WORKSPACE\com\tutorialspoint\xstream>javac XStreamTester.java

Now run the XStreamTester to see the result −

C:\XStream_WORKSPACE\com\tutorialspoint\xstream>java XStreamTester

Verify the output as follows −

<?xml version = "1.0" encoding = "UTF-8"?>
<student name = "Mahesh">
      <description>My first assignment.</description>

      <description>My Second assignment.</description>

In order to instruct the XStream framework to process annotation, you need to add the following command before serializing xml.