The javadoc for static method setDataContentHandlerFactory makes it clear, that using this call overrides any other possible source for deriving a DataContentHandler.

However, if a DataHandler has been created, and any method which uses a DataContentHandler (ie which causes the private method getDataContentHandler, to be called) has been called, then a subsequent call to the static method setDataContentHandlerFactory will not effect this DataHandler, because the first line of code in getDataContentHandler is:

if (dataContentHandler != null)
return dataContentHandler;

Besides violating the spec for setDataContentHandlerFactory, a more subtle issue is that this makes the the resulting behavior somewhat non-deterministic in relationship to the documentation. There's no defined semantic for when calling setDataContentHandlerFactory ceases to affect any given existing DataHandler instance.