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https://issues.apache.org/jira/browse/JENA-1634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16689538#comment-16689538
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Andy Seaborne edited comment on JENA-1634 at 11/16/18 4:09 PM:
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"Stream" refers to the fact that these writers do not need to analysis the
whole of the RDF data before writing. "Pretty" formats need to analysis in
order to build datastructures to guide the output process before starting to
generate thrie output.
{{RDFWriterRegistry}} holds all the registered writers; {{StreamRDFWriter}}
gives a stronger guarantee about a subset of these - that the output streams.
The default RDFFormat for RDF/XML does not stream; RDFFormat.RDFXML_PLAIN does.
{{RDFDataMgr}} uses {{RDFWriterRegistry}}.
If you want a fallback, then check with {{StreamRDFWriter.registered}} and if
it returns null, use {{RDFWriterRegistry}}.
Or just lookup in {{RDFWriterRegistry}}. For a streaming format, like
RDFFormat.TURTLE_BLOCKS, you will get a streaming writer (in fact the same
writer code).
See {{ModLangOutput}} and how it handles {{argOutput}}.
On reading all RDF formats stream.
was (Author: andy.seaborne):
{{RDFWriterRegistry}} holds all the registered writers; {{StreamRDFWriter}}
gives a stronger guarantee about a subset of these - that the output streams.
The default RDFFormat for RDF/XML does not stream; RDFFormat.RDFXML_PLAIN does.
{{RDFDataMgr}} uses {{RDFWriterRegistry}}.
If you want a fallback, then check with {{StreamRDFWriter.registered}} and if
it returns null, use {{RDFWriterRegistry}}.
Or just lookup in {{RDFWriterRegistry}}. For a streaming format, like
RDFFormat.TURTLE_BLOCKS, you will get a streaming writer (in fact the same
writer code).
See {{ModLangOutput}} and how it handles {{argOutput}}.
On reading all RDF formats stream.
> StreamRDFWriter doesn't work with Lang or RDFFormat default instances.
> ----------------------------------------------------------------------
>
> Key: JENA-1634
> URL: https://issues.apache.org/jira/browse/JENA-1634
> Project: Apache Jena
> Issue Type: New Feature
> Components: RIOT
> Affects Versions: Jena 3.9.0
> Reporter: Marco Brandizi
> Priority: Major
>
> I have [some
> code|https://github.com/Rothamsted/ondex-knet-builder/blob/master/modules/rdf-export-2/src/main/java/net/sourceforge/ondex/rdf/export/RDFFileExporter.java]
> 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|https://github.com/marco-brandizi/jena-stream-writer-issue/blob/master/src/test/java/info/marcobrandizi/rdf/test/JenaWritersTest.java]:
> 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.
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