RDFWriter rdfWriter = rdfWriterFactory.getWriter(out);
rdfWriter.getWriterConfig().set(JSONLDSettings.JSONLD_MODE, JSONLDMode.COMPACT);
rdfWriter.handleNamespace("ex", exNs);
rdfWriter.startRDF();
rdfWriter.handleStatement(st1);
rdfWriter.endRDF();
ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());
RDFParser rdfParser = rdfParserFactory.getParser();
ParserConfig config = new ParserConfig();
config.set(BasicParserSettings.FAIL_ON_UNKNOWN_DATATYPES, true);