On 8 April 2013 22:13, Jörg Schaible <[email protected]> wrote: > Stuart Rossiter wrote: > > > On 6 April 2013 21:21, Jörg Schaible > > <[email protected]> wrote: > > > >> Hi Stuart, > >> > >> Stuart Rossiter wrote: > >> > >> > Hi. With the latest XStream 1.4.4 (on Windows with Java 6), using the > >> StAX > >> > driver instead of the XPP3 or JAXP DOM one means that toXML includes > >> > the XML declaration (<?xml version="1.0"?>) *and* doesn't pretty-print > >> > the string. The other drivers work fine. > >> > > >> > This looks like a consistency bug, given that the declaration should > >> never > >> > be written, and it should always be pretty-printed. However, the JIRA > >> > log-in link doesn't allow me to request a userid as the XStream pages > >> > suggest. (It says 'contact your JIRA admin'.) > >> > > >> > So: > >> > (a) Is this a bug? (Browsing JIRA suggests none registered.) > >> > >> No. Actually we normally have only XML parsers, but StAX is the one of > >> the view XML frameworks that also includes a writer. And XStream is > using > >> the defaults of the framework. Note, that the default for all the other > >> parsers (PrettyPrintWriter of XStream) does not support namespaces. > >> > >> > > That makes sense, but surely XStream should present a consistent API that > > isn't dependent on the driver used? > > > > The XStream toXML method Javadoc states that it "Serialize[s] an object > to > > a pretty-printed XML String". > > > > The FAQ states: > > Q. Why does XStream not write an XML declaration? > > A. XStream is designed to write XML snippets, so you can embed its output > > into an existing stream or string. You can write the XML declaration > > yourself into the Writer before using it to call XStream.toXML(writer). > > > > So, if the wrapped driver doesn't do this by default, shouldn't XStream > be > > doing it (either by configuring the driver internally or parsing its > > outputs)? Particularly since XStream has no functionality to > pretty-print > > or remove the header 'manually'. (I appreciate that there are probably > > XML-related libraries that can do this for me, but still...) > > > > Am I missing something here? > > That's the point: XStream does *not* write the XML header. However, in case > of StAX it is written by javax.xml.stream.XMLStreamWriter. XStream is > limited to its capabilities. Iy you have no need for namespaces, you can > use > XStream's PrettyPrintWriter instead. > > > I'm really sorry to drag this out (and possibly offend you) but, unless I'm missing something *massive*, I really don't understand your response. It is irrelevant whether it is XStream or dependency code *actually* writing the XML header and/or doing the pretty-printing. XStream is providing an abstracted interface for XML serialisation of objects. The interface contract states that toXML pretty-prints XML and doesn't include an XML header.
So either: (a) The Javadoc and FAQ entry need changing to make clear that the header-writing and pretty-printing are governed by the driver chosen. (Really the Javadoc should mention the header-writing, not leaving that detail to the FAQ.) (b) XStream should honour this contract by whatever means necessary (e.g., if the STaX driver is being used, use STaX to generate the XML and then strip off the header and pretty-print it before returning). I'm just really confused since this is a standard principles-of-API-design thing isn't it (with (b) being the 'normal' option in such circumstances)?? Stuart
