package org.mulgara.jena;
/*
* (c) Copyright 2008 Hewlett-Packard Development Company, LP
* All rights reserved.
* [See end of file]
*/
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import org.apache.log4j.Logger;
import org.mulgara.query.*;
import org.mulgara.server.Session;
import com.hp.hpl.jena.graph.Graph;
import com.hp.hpl.jena.graph.Node;
import com.hp.hpl.jena.graph.Triple;
import com.hp.hpl.jena.graph.query.BindingQueryPlan;
import com.hp.hpl.jena.graph.query.Domain;
import com.hp.hpl.jena.graph.query.Query;
import com.hp.hpl.jena.graph.query.SimpleQueryHandler;
import com.hp.hpl.jena.graph.query.TreeQueryPlan;
import com.hp.hpl.jena.shared.JenaException;
import com.hp.hpl.jena.util.iterator.ExtendedIterator;
import com.hp.hpl.jena.util.iterator.NiceIterator;
/**
* Handles Jena query patterns in Mulgara
*
* @author Andy Seaborne
* @copyright © 2008 Hewlett-Packard Development Company, LP
*/
public class PatternMulgara extends SimpleQueryHandler {
// Scruffy
private static final Logger logger = Logger.getLogger(PatternMulgara.class);
GraphMulgara graphMulgara;
/**
* @param graph
*/
public PatternMulgara(GraphMulgara graph) {
super(graph);
graphMulgara = graph;
}
@Override
final public TreeQueryPlan prepareTree(Graph pattern) {
throw new RuntimeException("prepareTree - Chris says this will not be called");
}
@SuppressWarnings("unchecked")
static List<Order> x = Collections.EMPTY_LIST;
@Override
public BindingQueryPlan prepareBindings(Query q, Node [] variables) {
Map<Node, Variable> vars_jm = new HashMap<Node,Variable>();
List<Variable> proj = new ArrayList<Variable>() ; // Mirrors Node [] variables
int idx = 0;
// Allocate variables. Projection and pattern
for (int i = 0; i < variables.length; i++) {
Node v = variables[i] ;
idx = allocVar(vars_jm, proj, v, idx) ;
}
@SuppressWarnings("unchecked")
List<Triple> pattern = q.getPattern() ;
for (Triple t: pattern) {
Node s = t.getSubject();
Node p = t.getPredicate();
Node o = t.getObject();
idx = allocVar(vars_jm, null, s, idx);
idx = allocVar(vars_jm, null, p, idx);
idx = allocVar(vars_jm, null, o, idx);
}
// Mulgara constraint
ConstraintExpression constraint = null;
for (Triple t: pattern) {
constraint = compileTriplePattern(constraint, vars_jm,
t.getSubject(), t.getPredicate(), t.getObject());
}
// Mulgara query
org.mulgara.query.Query query = new org.mulgara.query.Query(
proj, // Projection
new GraphResource(graphMulgara.getModelURI()), // Model to query
constraint, // WHERE
null, // HAVING
x, // ORDER
null, // LIMIT
0, // OFFSET
true, // DISTINCT
new UnconstrainedAnswer() // Initial Answer
);
// Wrap it up into an query execution instance.
return new BindingQueryPlanMulgara(query, graphMulgara.getSession(), proj);
}
private static int allocVar(Map<Node, Variable> vars_jm, List<Variable> proj, Node v, int idx) {
if (!v.isVariable()) return idx ;
if (!vars_jm.containsKey(v)) {
String vn = "v"+(idx++);
Variable vm = new Variable(vn);
vars_jm.put(v, vm);
if (proj != null) proj.add(vm);
}
return idx ;
}
private ConstraintExpression compileTriplePattern(ConstraintExpression c,
Map<Node,Variable> vars_jm,
Node s, Node p, Node o) {
try {
ConstraintElement sElt = compile(vars_jm, s);
ConstraintElement pElt = compile(vars_jm, p);
ConstraintElement oElt = compile(vars_jm, o);
ConstraintExpression c2 = new ConstraintImpl(sElt, pElt, oElt);
if (c != null) return new org.mulgara.query.ConstraintConjunction(c, c2);
else return c2;
} catch (Exception ex) {
throw new JenaException("Failed to compile: ("+s+" "+p+" "+o+")");
}
}
private ConstraintElement compile(Map<Node, Variable> vars, Node n) throws URISyntaxException {
if (n.isVariable()) return vars.get(n);
else return Jenara.n2v(n, graphMulgara.getSession());
}
static class BindingQueryPlanMulgara implements BindingQueryPlan {
org.mulgara.query.Query query;
AnswerIterator iter;
private List<Variable> projection;
private Session session;
public BindingQueryPlanMulgara(org.mulgara.query.Query query,
Session session,
List<Variable> proj) {
this.query = query ;
this.session = session ;
this.projection = proj ;
}
public ExtendedIterator executeBindings() {
try {
Answer answer = session.query(query);
// Must reset
answer.beforeFirst();
iter = new AnswerIterator(answer, projection);
return iter;
} catch (Exception ex) {
throw new JenaException("Failed to executeBindings");
}
}
}
// original comment of extending NiceIterator<Domain>
static class AnswerIterator extends NiceIterator {
private Answer answer;
private Domain slot = null;
private boolean finished = false;
private List<Variable> proj;
AnswerIterator(Answer answer, List<Variable> proj) {
this.answer = answer;
this.proj = proj;
}
@Override
public boolean hasNext() {
if (finished) return false;
if (slot != null) return true;
try {
if (! answer.next()) {
close();
return false;
}
slot = convert();
} catch (TuplesException ex) {
logger.warn("Exception iterating Mulgara answer", ex);
return false;
}
return slot != null;
}
Domain convert() throws TuplesException {
Domain d = new Domain(proj.size());
for (int i = 0; i < proj.size(); i++) {
Node n = Jenara.o2n((org.jrdf.graph.Node)answer.getObject(i));
d.setElement(i, n);
}
return d ;
}
@Override
public Object next() {
if (!hasNext()) throw new NoSuchElementException("AnswerIterator.next");
Domain d = slot;
slot = null;
return d;
}
@Override
public void close() {
if (finished) return;
finished = true;
try {
answer.close();
} catch (TuplesException ex) {
logger.warn("Exception closing answer", ex);
}
}
@Override
public void remove() { throw new UnsupportedOperationException(); }
}
}
/*
* (c) Copyright 2008 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.
*/