Package arq.examples.bgpmatching

Source Code of arq.examples.bgpmatching.StageAltMain

/*
* (c) Copyright 2007, 2008, 2009 Hewlett-Packard Development Company, LP
* All rights reserved.
* [See end of file]
*/

package arq.examples.bgpmatching;

import org.openjena.atlas.lib.StrUtils ;

import com.hp.hpl.jena.query.ARQ ;
import com.hp.hpl.jena.query.Query ;
import com.hp.hpl.jena.query.QueryExecution ;
import com.hp.hpl.jena.query.QueryExecutionFactory ;
import com.hp.hpl.jena.query.QueryFactory ;
import com.hp.hpl.jena.rdf.model.Model ;
import com.hp.hpl.jena.rdf.model.ModelFactory ;
import com.hp.hpl.jena.rdf.model.Property ;
import com.hp.hpl.jena.rdf.model.Resource ;
import com.hp.hpl.jena.sparql.engine.main.StageGenerator ;
import com.hp.hpl.jena.sparql.util.QueryExecUtils ;

/** Example to execute a query but handle the
*  basic graph patterns in the query in some special way.
*  Stages are one step in executing a basic graph pattern (BGP).
*  A StageGenerator builds a StageList and the stage list
*  is executes with the output (a QueryIterator) of the previous
*  stage fed int the current stage.
*/ 

public class StageAltMain
{
    static String NS = "http://example/" ;

    public static void main(String[] argv)
    {
        String[] queryString =
        {
            "PREFIX ns: <"+NS+">" ,
            "SELECT ?v ",
            "{ ?s ns:p1 'xyz' ;",
            "     ns:p2 ?v }"
        } ;

        // The stage generator to be used for a query execution
        // is read from the context.  There is a global context, which
        // is cloned when a query execution object (query engine) is
        // created.
       
        // Normally, StageGenerators are chained - a new one inspects the
        // execution request and sees if it handles it.  If it does not,
        // it sends the request to the stage generator that was already registered.
       
        // The normal stage generator is registerd in the global context.
        // This can be replaced, so that every query execution uses the
        // alternative stage generator, or the cloned context can be
        // alter so that just one query execution is affected.

        // Change the stage generator for all queries ...
        if ( false )
        {
            StageGenerator origStageGen = (StageGenerator)ARQ.getContext().get(ARQ.stageGenerator) ;
            StageGenerator stageGenAlt = new StageGeneratorAlt(origStageGen) ;
            ARQ.getContext().set(ARQ.stageGenerator, stageGenAlt) ;
        }
       
        Query query = QueryFactory.create( StrUtils.strjoin("\n", queryString)) ;
        QueryExecution engine = QueryExecutionFactory.create(query, makeData()) ;
       
        // ... or set on a per-execution basis.
        if ( true )
        {
            StageGenerator origStageGen = (StageGenerator)engine.getContext().get(ARQ.stageGenerator) ;
            StageGenerator stageGenAlt = new StageGeneratorAlt(origStageGen) ;
            engine.getContext().set(ARQ.stageGenerator, stageGenAlt) ;
        }
       
        QueryExecUtils.executeQuery(query, engine) ;
    }
   
    private static Model makeData()
    {
        Model model = ModelFactory.createDefaultModel() ;
        Resource r = model.createResource(NS+"r") ;
        Property p1 = model.createProperty(NS+"p1") ;
        Property p2 = model.createProperty(NS+"p2") ;
        model.add(r, p1, "xyz") ;
        model.add(r, p2, "abc") ;
        return model ;
    }
}

/*
* (c) Copyright 2007, 2008, 2009 Hewlett-Packard Development Company, LP
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
*    derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
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