Nevermind. I realized the answer shortly after I asked the question.
A new Transformer must be created.
A Transformer must be created with an XSL file to transform an XML file.
The Transformer with the XSL can pass XML as input and create a document
directly using an output created from the Fop handler.
The Transformer with the XSL can pass XML as input and create FO output
using an empty SAX stream output object.
A Transformer without an XSL can pass FO as input and create a document
using an output created from the Fop handler.
