Details
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New Feature
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Status: Closed
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Major
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Resolution: Information Provided
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Jena 3.9.0
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None
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None
Description
I have some code that writes RDF to a file, starting from a Model. This is invoked many times over the same FileOutput stream, by many threads that are producing RDF in parallel.
The output type can be selected by the invoker, by passing Lang or RDFFormat instances. Because of the way it works, that output will be RDFFormat.TURTLE_BLOCKS most of times. However, there might be cases of small output, where the user might want to send in formats like Lang.RDFXML.
Now, the problem is in the latter case the StreamRDFWriter.getWriterStream() doesn't work. I've isolated the issue here: I get messages like "No serialization for language Lang:RDF/XML" and, looking at the sources, it seems that StreamRDFWriter recognises only Lang/RDFFormat instances set in its own registry.
The same languages/variants work fine when I use the RDFDataMgr approach. This makes me guess/hope that data manager is able to work in a stream fashion, when the received RDF variants supports it.
Whatever it is, I think this is wrong, or at least should be documented better, in particular, the documentation should say what to do in a situation like mine, where it's not known in advance if we're going to deal with streaming or not. Ideally, StreamRDFWriter should fallback to non-streaming, or trigger a specific exception when dealing with a streaming-incompatible format, so that the invoker can take fallback actions.
I'm using the whole apache-jena-libs as Jena dependency.
I suppose this applies to reading too.