[namedgraphs] Persisting a TRIG file multiple times

[Arun R. <rao...@gm...>]

Hi,

I was trying to read a TRIG file multiple times into memory and then write
it back without making changes and I ran into errors with the parser.

Here is the sample code:

        String filename = "test.trig";
        NamedGraphSet graphSet = new NamedGraphSetImpl();
        NamedGraphModel ngModel = new NamedGraphModel(graphSet, "");
        InputStream in = FileManager.get().open(filename);
        if (in == null) {
            throw new IllegalArgumentException("File: not found");
        }

        graphSet.read(in, "TRIG", null);

        try {
            ngModel.write(new PrintWriter(new File(filename)), "TRIG");
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

test.trig:

@prefix ns0:     <http://example.com/> .

<http://graph1.com/> {ns0:aResource
          ns0:pProperty ns0:bResource ;
          ns0:qProperty ns0:xResource .
}

The first run, it creates an extra line:

<> {} in the TRIG file

The second run, it creates an extra line:

<null> {} in the TRIG file

The third run fails.

If however, I change:
graphSet.read(in, "TRIG", null);

to:
graphSet.read(in, "TRIG", "");

it works fine.

What could be the issue? Is this a bug?

Regards,
Arun