JAXB is good until I need to do something complex. What are the alternatives?

Question

JAXB works well until I need to do something like serialize beans for which I cannot modify the source. If the bean doesn't have a default constructor or if it refers to objects I want to mark transient then I'm stuck writing a separate bean which I can annotate and then manually copy the information over from the other bean.

For instance, I wanted to serialize exception objects, but found that the only way to do that was use a hack that required using com.sun.* classes.

So, what alternatives are there? What's the next most popular xml serializing api? It would be nice to be able to do things like:

• Choose at serialization time whether to include certain fields in the result. (marking things transient when running the serializer).

• Handle loops in the object graph by using references or something other than just dying.

• Perhaps annotate an object so that in version 1 it serializes things in one way and in version 2 it serializes them in another. Then when serializing I just choose which version of the object ot serialize.

• Have a way to generate XSDs from annotations on an object.

Basically I just want more flexibility than I currently have with JAXB.

Answer 1

XStream is a popular XML serialisation library that claims to be able to serialize just about anyting, regardless of constructors or other problems (even deserialize final fields). Give it a try.

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.

Answer 2

Well the standard answer for wanting a uber configurable serialisation framework is xstream.

Answer 3

Also look at JIBX. It's a good xml<->object mapper. My experience is though that if your objects have a somewhat funky relationships it's often easier to create a wrapper object that hides that complexity and then map that object with JIBX.

Answer 4

JAXB is a spec, so you can pick from different implementations. EclipseLink JAXB (MOXy) has extensions for what you are asking:

Externalized Metadata

Useful when dealing with classes for which you cannot annotate the source or to apply multiple mappings to an object model.

• http://wiki.eclipse.org/EclipseLink/Examples/MOXy/EclipseLink-OXM.XML

XPath Based Mapping

For true meet-in-the-middle OXM mapping:

• http://bdoughan.blogspot.com/2010/09/xpath-based-mapping-geocode-example.html
• http://bdoughan.blogspot.com/2010/07/xpath-based-mapping.html
• http://wiki.eclipse.org/EclipseLink/Examples/MOXy/GettingStarted/MOXyExtensions

JPA Compatibility

Including support for bi-directional relationships.

• http://bdoughan.blogspot.com/2010/07/jpa-entities-to-xml-bidirectional.html
• http://wiki.eclipse.org/EclipseLink/Examples/MOXy/JPA