BR created JENA-2051:
------------------------
Summary: Union Model Returns Empty Model Even When Default Model
Contains Statements
Key: JENA-2051
URL: https://issues.apache.org/jira/browse/JENA-2051
Project: Apache Jena
Issue Type: Bug
Reporter: BR
I'm using Jena 3.15.0.
When I try to use Dataset#getUnionModel no statements are returned in the
scenario below.
The work around to provide your own union method seems to be reasonable. This
is also shown in the test case below.
{code}
private String unionOfJsonLdGraphs(List<String> jsonLdGraphs) {
return jsonLdGraphs.stream()
.map(graph -> from(graph))
.flatMap(ContentProfileGraphExtractorImpl::modelsFromDataSet)
// Why did this not work?
//.map(Dataset::getUnionModel)
.reduce(this::union)
.map(ContentProfileGraphExtractorImpl::modelToString)
.orElse("{}");
}
private static Stream<Model> modelsFromDataSet(Dataset dataset) {
Stream<Model> namedModels =
stream(spliteratorUnknownSize(dataset.listNames(), ORDERED),
false).map(graphName->dataset.getNamedModel(graphName));
Stream<Model> defaultModel = of(dataset.getDefaultModel());
return concat(defaultModel, namedModels);
}
private Model union(Model modelA, Model modelB) {
if(null!=modelA && null!=modelB) {
return modelA.union(modelB);
} else if(null!=modelA) {
return modelA;
} else if(null!=modelB) {
return modelB;
} else {
throw new RuntimeException();
}
}
/**
* Creates a String containing the JSON-LD of the Model.
*
* @see
https://github.com/apache/jena/blob/master/jena-arq/src-examples/arq/examples/riot/Ex_WriteJsonLD.java
* @see https://json-ld.org/spec/latest/json-ld-framing/
* @see https://w3c.github.io/json-ld-framing/
*/
private static String modelToString(Model model) {
Map<String, Object> frame = new HashMap<>();
Map<String, Object> context = new HashMap<>();
context.put("@vocab",
"https://data.elsevier.com/lifescience/entellect/patent/";);
frame.put("@context", context);
// Construct Frame
Context serializationContext = new Context();
serializationContext.put(JSONLD_FRAME, frame);
ByteArrayOutputStream outputStream = new
ByteArrayOutputStream();
RDFWriter.create().format(JSONLD_FRAME_PRETTY).source(model).context(serializationContext)
.output(outputStream);
return new String(outputStream.toByteArray(), UTF_8);
}
{code}
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