[JENA-2302] RowSetReaderJSON is not streaming

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Implemented
• Affects Version/s: Jena 4.5.0
• Fix Version/s: Jena 4.5.0
• Component/s: ARQ
• Assignee: Claus Stadler
• Reporter: Claus Stadler
• Created: 07/Mar/22 14:24
• Updated: 04/May/22 21:21
• Resolved: 09/Apr/22 13:56

Description

Retrieving all data from our TDB2 endpoint with jena 4.5.0-SNAPSHOT is no longer streaming for the JSON format. I tracked the issue to RowSetReaderJson which reads everything into in memory (and then checks whether it is a SPARQL ASK result)

public class RowSetReaderJson {
        private void parse(InputStream in) {
            JsonObject obj = JSON.parse(in); // !!! Loads everything !!!

            // Boolean?
            if ( obj.hasKey(kBoolean) ) { ... }
    }
}

Streaming works when switching the to RS_XML in the example below:

public class Main {
    public static void main(String[] args) {
        System.out.println("Test Started");
        try (QueryExecution qe = QueryExecutionHTTP.create()
                .acceptHeader(ResultSetLang.RS_JSON.getContentType().getContentTypeStr())
                .endpoint("http://moin.aksw.org/sparql").queryString("SELECT * { ?s ?p ?o }").build()) {
            qe.execSelect().forEachRemaining(System.out::println);
        }
        System.out.println("Done");
    }
}

For completeness, I can rule out any problem with TDB2 because streaming of JSON works just fine with:

curl --data-urlencode "query=select * { ?s ?p ?o }"  "http://moin.aksw.org/sparql"

Issue Links

• links to: GitHub Pull Request #1253