Java library to serialize objects to XML and back again

 The features of the XStream library are:
 .
  - Ease of use. A high level facade is supplied that simplifies common
    use cases.
  - No mappings required. Most objects can be serialized without need
    for specifying mappings.
  - Performance. Speed and low memory footprint are a crucial part of
    the design, making it suitable for large object graphs or systems
    with high message throughput.
  - Clean XML. No information is duplicated that can be obtained via
    reflection. This results in XML that is easier to read for humans
    and more compact than native Java serialization.
  - Requires no modifications to objects. Serializes internal fields,
    including private and final. Supports non-public and inner classes.
    Classes are not required to have default constructor.
  - Full object graph support. Duplicate references encountered in the
    object-model will be maintained. Supports circular references.
  - Integrates with other XML APIs. By implementing an interface,
    XStream can serialize directly to/from any tree structure (not just
    XML).
  - Customizable conversion strategies. Strategies can be registered
    allowing customization of how particular types are represented as
    XML.
  - Error messages. When an exception occurs due to malformed XML,
    detailed diagnostics are provided to help isolate and fix the
    problem.
  - Alternative output format. The modular design allows other output
    formats. XStream ships currently with JSON support and morphing.