XStream

XStream Library
Developer(s)	Codehaus
Initial release	January 1, 2004; 20 years ago
Stable release	1.4.20 / December 24, 2022; 22 months ago
Written in	Java
Operating system	Cross-platform
License	BSD-style license
Website	x-stream.github.io

XStream is a Java library to serialize objects to XML (or JSON) and back again.

XStream library

XStream uses reflection to discover the structure of the object graph to serialize at run time, and doesn't require modifications to objects. It can serialize internal fields, including private and final, and supports non-public and inner classes.^[1]

Object graph serialization

When serializing an object it serializes the full object graph. Duplicate references encountered in the object-model will be maintained. For example, using the following class CD

package com.thoughtworks.xstream;
public class Cd {
	private String id;

	private Cd bonusCd;

	Cd(String id, Cd bonusCd) {
		this.id = id;
		this.bonusCd = bonusCd;
	}

	Cd(String id) {
		this.id = id;
	}

	public String getId() {
		return id;
	}

	public Cd getBonusCd() {
		return bonusCd;
	}
}

and add some of these object to a list

Cd bj = new Cd("basement_jaxx_singles");
Cd mr = new Cd("maria rita");
		
List<Cd> order = new ArrayList<>();
order.add(mr);
// adds the same cd twice (two references to the same object)
order.add(bj);
order.add(bj);

// adds itself (cycle)
order.add(order);

XStream xstream = new XStream();
xstream.alias("cd", Cd.class);
System.out.println(xstream.toXML(order));

If the above code is executed with XStream's default relative references mode, it will generate the following XML:

<list>
  <cd>
    <id>maria rita</id>
  </cd>
  <cd>
    <id>basement_jaxx_singles</id>
  </cd>
  <cd reference="../cd[2]"/>
  <list reference=".."/>
</list>