[Tm4j-developers] Merge utility now uses TopicMapProvider; possible URI resolution issue in TopicMapProviderBase

[Florian G. H. <fg...@bk...>]

Hello,

I've now changed the rewritten Merge utility according to Kal's suggestio=
n of=20
using the TopicMapProviderImpl class. However, one issue arises (try the=20
Merge utility with "http://www.topicmaps.org/xtm/1.0/core.xtm" for an=20
illustration):

TopicMapProviderBase creates an InputSource from an InputStream. Let's sa=
y=20
that the stream was obtained by invoking the getInputStream() method on a=
=20
URLConnection because one was trying to read/add/merge a topic map identi=
fied=20
by a URL (a common scenario, I guess). The InputSource has no way of know=
ing=20
how to resolve URI's relative to the document that the InputStream=20
represents: for all it cares, it only deals with some InputStream, and=20
goodness knows where that stream might have come from. You would have to =
use=20
InputSource.setSystemId() in order for the InputSource to resolve relativ=
e=20
URIs correctly. So without that invocation of setSystemId(), the SAX pars=
er=20
isn't even able to parse the document if the !DOCTYPE declaration does no=
t=20
contain an absolute URI for the DTD (which is the case for core.xtm as=20
mentioned above).

It gets worse. AKAIK there is no way to determine for sure whether the=20
InputStream was obtained from a URLConnection: if, in contrast, a stream =
was=20
opened on a file, then fine, it's instanceof FileInputStream. Yet there i=
s no=20
such thing as a URLConnectionInputStream; URLConnection.getInputStream()=20
returns just a generic java.io.InputStream. It is (again, to the best of =
my=20
knowledge) impossible to determine what URL that InputStream was created=20
from, so even if TopicMapProviderBase did invoke InputSource.setSystemId(=
),=20
it would't know what system ID to use!

Am I getting something wrong or are we looking at a, um, feature here?
-- Florian

--=20
Florian G. Haas <fg...@bk...>

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