Stuart,
I can't see what might be going wrong from your code - could you show
how the DataSource was created in the first place and how data got into
it? Ideally, a complete, minimal example that I can run at my end.
(and the version of software would also be good).
What is quite odd is that:
> images.addNamedModel(id, mk.createDefaultModel().read(new
> ByteArrayInputStream(bytes.toString().getBytes()),""));
> images.addNamedModel(id, image);
which adds the data twice once as a new model and once as the original
data, in fact replaces the new with the original. addNamedModel is
replace if the name is already in use.
What is the query?
Andy
On 02/02/11 16:31, Stuart Kenny wrote:
Hi, I've been stuck trying to query a DataSource for the last few
days. The DataSource is being used as a store of models. One class
adds Models to the DataSource using addNamedModel, and a separate
class is meant to answer queries on this DataSource. When I try to
execute a query however I get no results:
Query query = QueryFactory.create(queryString);
QueryExecution qe = QueryExecutionFactory.create(query, getImages());
ResultSet results = qe.execSelect();
where getImages() returns the DataSource being used as a Model store.
Crazily if I create a new DataSource and then iterate through the
models, writing them out and then reading them back in, the query
works on this new DataSource:
ModelMaker mk = ModelFactory.createMemModelMaker();
DataSource images = DatasetFactory.create(mk.createDefaultModel());
for ( Iterator<String> imagesIter = getImages().listNames();
imagesIter.hasNext(); ){
String id = imagesIter.next();
Model image = getImages().getNamedModel(id);
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
BufferedOutputStream out = new BufferedOutputStream(bytes);
image.getWriter().write(image, out, "");
images.addNamedModel(id, mk.createDefaultModel().read(new
ByteArrayInputStream(bytes.toString().getBytes()),""));
images.addNamedModel(id, image);
}
Query query = QueryFactory.create(queryString);
QueryExecution qe = QueryExecutionFactory.create(query, images);
ResultSet results = qe.execSelect();
Just adding the models isn't enough, I have to write and read to new
Models to get it to work!
I can't really write all the models out and then re-read them to get a
query to succeed. Presumably using a DataSource in this way is
incorrect. I'm new to this so I'm obviously doing something
fundamentally wrong.
Would be very grateful for any help.
Thanks.
