Examples of com.hp.hpl.jena.query.Query

com.hp.hpl.jena.query.Query
The data structure for a query as presented externally. There are two ways of creating a query - use the parser to turn a string description of the query into the executable form, and the programmatic way (the parser is calling the programmatic operations driven by the quyery string). The declarative approach of passing in a string is preferred. Once a query is built, it can be passed to the QueryFactory to produce a query execution engine. @see QueryExecutionFactory @see ResultSet

        
        // Query string.
        String queryString = prolog + NL +
            "SELECT ?title WHERE {?x dc:title ?title}" ; 
        
        Query query = QueryFactory.create(queryString) ;
        // Print with line numbers
        query.serialize(new IndentedWriter(System.out,true)) ;
        System.out.println() ;
        
        // Create a single execution of this query, apply to a model
        // which is wrapped up as a Dataset

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    {
        // Call the function as java:arq.examples.ext.labelSearch or register it.
        String prologue = "PREFIX ext: <java:arq.examples.propertyfunction.>\n" ;


        String qs = prologue+"SELECT * { ?x ext:labelSearch 'EF' }" ;
        Query query = QueryFactory.create(qs) ;
        Model model = make() ;
        QueryExecution qExec = QueryExecutionFactory.create(query, model) ;
        try {
            ResultSet rs = qExec.execSelect() ;
            ResultSetFormatter.out(rs) ;

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        String s = StrUtils.strjoin("\n", 
            "PREFIX  rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#>" ,
            "PREFIX  rdfs:   <http://www.w3.org/2000/01/rdf-schema#>",
            "SELECT DISTINCT ?root { { ?root rdf:type ?ATYPE } UNION { ?root rdf:type ?t . ?t rdfs:subClassOf ?ATYPE } }") ;
        
        Query q = QueryFactory.create(s) ;
        QuerySolutionMap qsm = new QuerySolutionMap() ;
        qsm.add("ATYPE", atype) ;


        QueryExecution qExec = QueryExecutionFactory.create(q, model, qsm);
        Resource r = (Resource)QueryExecUtils.getOne(qExec, "root") ;

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    @Override
    public void visit(ElementSubQuery el)
    {
        out.print("{ ") ;
        out.incIndent(INDENT) ;
        Query q = el.getQuery() ; 
        // It's SELECT query so no template formatter needed.
        Serializer.serializeARQ(q, out, 
                                new FormatterElement(out, context),
                                new FmtExprSPARQL(out, context),
                                null) ;

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    { return getExactlyOne(qs, DatasetFactory.create(model)) ; }
    
    /** Execute a query, expecting the result to be one row, one column.  Return that one RDFNode */
    public static RDFNode getExactlyOne(String qs, Dataset ds)
    {
        Query q = QueryFactory.create(qs) ;
        if ( q.getResultVars().size() != 1 )
            throw new ARQException("getExactlyOne: Must have exactly one result columns") ;
        String varname = q.getResultVars().get(0) ;
        QueryExecution qExec = QueryExecutionFactory.create(q, ds);
        return getExactlyOne(qExec, varname) ;
    }

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        // Any substitution is also safe because it replaced variables by values. 
        Op opRemote = Rename.reverseVarRename(op.getSubOp(), true) ;


        //Explain.explain("HTTP", opRemote, context) ;
        
        Query query ;
        
        // Comment (for the future?)
//        if ( false )
//        {
//            // ***** Interacts with substitution.

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    public static Path parse(String str, PrefixMapping pmap)
    { return parse(str, new Prologue(pmap)) ; }
    
    public static Path parse(String str, Prologue prologue)
    {
        Query query = new Query(prologue) ;
        Reader in = new StringReader(str) ;
        ARQParser parser = new ARQParser(in) ;


        try {
            query.setStrict(true) ;
            parser.setQuery(query) ;
            return parser.PathUnit() ;
        } catch (com.hp.hpl.jena.sparql.lang.arq.ParseException ex)
        {
            throw new QueryParseException(ex.getMessage(),

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        IndentedLineBuffer buff = new IndentedLineBuffer() ;
        query.serialize(buff, query.getSyntax()) ;
        
        String tmp = buff.toString() ;
        
        Query query2 = null ;
        try {
            String baseURI = null ;
            if ( ! query.explicitlySetBaseURI() )
                // Not in query - use the same one (e.g. file read from) .  
                baseURI = query.getBaseURI() ;
            
            query2 = QueryFactory.create(tmp, baseURI, query.getSyntax()) ;
            
            if ( query2 == null )
                return ;
        } catch (UnsupportedOperationException ex)
        {
            // No parser after all.
            return ;
        }
        catch (QueryException ex)
        {
            System.err.println(tmp) ;
            throw new QueryCheckException("could not parse output query", ex) ;
        }
        
        if ( query.hashCode() != query2.hashCode() )
            throw new QueryCheckException("reparsed query hashCode does not equal parsed input query \nQuery (hashCode: " + query.hashCode() + ")=\n" + query + "\n\nQuery2 (hashCode: " + query2.hashCode() + ")=\n" + query2) ;
        
        if ( ! query.equals(query2) ) 
            throw new QueryCheckException("reparsed output does not equal parsed input") ;
    }

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    private static class SubQueryScopeChecker extends ElementVisitorBase
    {
        @Override
        public void visit(ElementSubQuery el)
        {
            Query query = el.getQuery() ;
            checkQueryScope(query) ;
            // Recursively check sub-queries in sub-queries.
            check(el.getQuery()) ;
        }

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        return query ;
    }
    
    public static Element parseElement(String string)
    {
        final Query query = new Query () ;
        Action action = new Action() {
            @Override
            public void exec(SPARQLParser11 parser) throws Exception
            {
                Element el = parser.GroupGraphPattern() ;
                query.setQueryPattern(el) ;
            }
        } ;
        perform(query, string, action) ;
        return query.getQueryPattern() ;
    }

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Related Classes of com.hp.hpl.jena.query.Query

arq.examples.AlgebraEx

arq.examples.bgpmatching.StageAltMain

arq.examples.propertyfunction.labelSearch

arq.qparse

arq.rsparql

at.tuwien.minireef.MiniREEF

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