public abstract Source marshal (ElementT n, ValidationEventHandler errorHandler)

This method is called when a JAXB provider needs to marshal an element to XML.

If non-null, the returned Source must contain a whole document rooted at one element, which will then be weaved into a bigger document that the JAXB provider is marshalling.

errorHandler     Receives any errors happened during the process of converting an element into a Source. The caller must provide a non-null error handler.

Returns:  null if there was an error. The error should have been reported to the handler.