A Generic, Reusable Solution for Marshalling Java Objects to/from XML

olving the same problems over and over again can be quite tiring for a software engineer, yet the object persistence wheel has been reinvented more times than I'd like to count. Thankfully, the industry is centralizing on XML because it can represent object relationships very well, and it is architecture and language-agnostic by nature. XML is now at the backbone of most client/server applications, from XHTML to SOAP web services to RESTful services, preferences, persistence, and configuration.

However, even with the advent of XML, mapping from objects such as Java class instances to XML is not always trivial. In particular, using a "contract first" approach that defines an XML schema, namespaces, and XML data types can be arduous. Object-to-XML mapping (OXM) libraries such as JAXB, XMLBeans, and XStream have made OXM easier, and they've helped to define APIs that serve as the foundation of serialization for tools such as Spring Web Services (Spring-WS). These libraries work by generating classes or using Java annotations to map the objects to a defined XML schema automatically. So the application developer simply instantiates an object, populates the data, and tells the library to marshal the object to well-formed XML. The process then works in reverse when the application unmarshals the XML back into objects by feeding the XML into the library.