Examples with QueryIteratorResultSet org.apache.jena.sparql.engine.iterator.QueryIteratorResultSet used on opensource projects

Example 1 with QueryIteratorResultSet

use of org.apache.jena.sparql.engine.iterator.QueryIteratorResultSet in project jena by apache.

the class Service method exec.

/**
     * Executes a service operator
     * 
     * @param op
     *            Service
     * @param context
     *            Context
     * @return Query iterator of service results
     */
public static QueryIterator exec(OpService op, Context context) {
    if (context != null && context.isFalse(serviceAllowed))
        throw new QueryExecException("SERVICE execution disabled");
    if (!op.getService().isURI())
        throw new QueryExecException("Service URI not bound: " + op.getService());
    // This relies on the observation that the query was originally correct,
    // so reversing the scope renaming is safe (it merely restores the
    // algebra expression).
    // Any variables that reappear should be internal ones that were hidden
    // by renaming in the first place.
    // Any substitution is also safe because it replaced variables by
    // values.
    Op opRemote = Rename.reverseVarRename(op.getSubOp(), true);
    // JENA-494 There is a bug here that the renaming means that if this is
    // deeply nested and joined to other things at the same level of you end
    // up with the variables being disjoint and the same results
    // The naive fix for this is to map the variables visible in the inner
    // operator to those visible in the rewritten operator
    // There may be some cases where the re-mapping is incorrect due to
    // deeply nested SERVICE clauses
    Map<Var, Var> varMapping = new HashMap<>();
    Set<Var> originalVars = OpVars.visibleVars(op);
    Set<Var> remoteVars = OpVars.visibleVars(opRemote);
    boolean requiresRemapping = false;
    for (Var v : originalVars) {
        if (v.getName().contains("/")) {
            // A variable which was scope renamed so has a different name
            String origName = v.getName().substring(v.getName().lastIndexOf('/') + 1);
            Var remoteVar = Var.alloc(origName);
            if (remoteVars.contains(remoteVar)) {
                varMapping.put(remoteVar, v);
                requiresRemapping = true;
            }
        } else {
            // A variable which does not have a different name
            if (remoteVars.contains(v))
                varMapping.put(v, v);
        }
    }
    // Explain.explain("HTTP", opRemote, context) ;
    Query query;
    //@formatter:off
    // Comment (for the future?)
    //        if ( false )
    //        {
    //            // ***** Interacts with substitution.
    //            Element el = op.getServiceElement().getElement() ;
    //            if ( el instanceof ElementSubQuery )
    //                query = ((ElementSubQuery)el).getQuery() ;
    //            else
    //            {
    //                query = QueryFactory.create() ;
    //                query.setQueryPattern(el) ;
    //                query.setResultVars() ;
    //            }
    //        }
    //        else
    //@formatter:on
    query = OpAsQuery.asQuery(opRemote);
    Explain.explain("HTTP", query, context);
    String uri = op.getService().getURI();
    HttpQuery httpQuery = configureQuery(uri, context, query);
    InputStream in = httpQuery.exec();
    // Read the whole of the results now.
    // Avoids the problems with calling back into the same system e.g.
    // Fuseki+SERVICE <http://localhost:3030/...>
    ResultSet rs = ResultSetFactory.fromXML(in);
    QueryIterator qIter = QueryIter.materialize(new QueryIteratorResultSet(rs));
    // And close connection now, not when qIter is closed.
    IO.close(in);
    // nested SERVICE clauses
    if (requiresRemapping) {
        qIter = QueryIter.map(qIter, varMapping);
    }
    return qIter;
}