/**
* Copyright (c) 2013, Institute of Information Systems (Sven Groppe and contributors of LUPOSDATE), University of Luebeck
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
* following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this list of conditions and the following
* disclaimer.
* - 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.
* - Neither the name of the University of Luebeck nor the names of its contributors may be used to endorse or promote
* products derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
*/
package lupos.engine.operators.singleinput.federated;
import java.io.IOException;
import java.util.HashSet;
import java.util.Iterator;
import lupos.datastructures.bindings.Bindings;
import lupos.datastructures.bindings.BindingsFactory;
import lupos.datastructures.items.Item;
import lupos.datastructures.items.Variable;
import lupos.datastructures.items.literal.LazyLiteral;
import lupos.datastructures.items.literal.Literal;
import lupos.datastructures.items.literal.URILiteral;
import lupos.datastructures.queryresult.ParallelIterator;
import lupos.datastructures.queryresult.QueryResult;
import lupos.endpoint.client.Client;
import lupos.engine.operators.messages.BoundVariablesMessage;
import lupos.engine.operators.messages.Message;
import lupos.sparql1_1.Node;
/**
* For all those approaches, which must join the result of the sparql endpoint afterwards with the original queryresult (computed from the local data (and/or other service calls))
*/
public abstract class FederatedQueryWithSucceedingJoin extends FederatedQuery {
public FederatedQueryWithSucceedingJoin(final Node federatedQuery) {
super(federatedQuery);
}
@Override
public Message preProcessMessage(final BoundVariablesMessage msg) {
this.intersectionVariables = new HashSet<Variable>();
this.unionVariables = new HashSet<Variable>();
FederatedQuery.checkVariables(this.federatedQuery, this.unionVariables);
this.intersectionVariables.addAll(this.unionVariables);
final BoundVariablesMessage result = new BoundVariablesMessage(msg);
result.getVariables().addAll(this.unionVariables);
return result;
}
@Override
public QueryResult process(final QueryResult bindings, final int operandID) {
return FederatedQueryWithSucceedingJoin.process(bindings, this.endpoint, this.toStringQuery(bindings), this.bindingsFactory);
}
public static QueryResult process(final QueryResult bindings, final Item endpoint, final String fQuery, final BindingsFactory bindingsFactory){
if (!endpoint.isVariable()) {
try {
return Client.submitQuery(((URILiteral)endpoint).getString(), fQuery, bindingsFactory);
} catch (final Exception e) {
System.err.println(e);
e.printStackTrace();
}
} else {
// service call with variable
// it could be that several endpoints are asked, which we succeedingly ask for results...
// the same endpoints are not asked again!
return QueryResult.createInstance(new ParallelIterator<Bindings>(){
private final Iterator<Bindings> it = bindings.oneTimeIterator();
private final HashSet<URILiteral> alreadyAskedEndpoints = new HashSet<URILiteral>();
private Iterator<Bindings> currentIteratorQueryResult = this.getNextIteratorQueryResult();
@Override
public boolean hasNext() {
if(this.currentIteratorQueryResult==null){
return false;
}
while(!this.currentIteratorQueryResult.hasNext()){
this.currentIteratorQueryResult = this.getNextIteratorQueryResult();
if(this.currentIteratorQueryResult==null){
return false;
}
}
return true;
}
@Override
public Bindings next() {
if(this.hasNext()){
return this.currentIteratorQueryResult.next();
} else {
return null;
}
}
@Override
public void remove() {
this.it.remove();
}
@Override
public void close() {
if(this.it instanceof ParallelIterator){
((ParallelIterator<Bindings>)this.it).close();
}
}
private Iterator<Bindings> getNextIteratorQueryResult(){
final URILiteral endpointURI = this.nextEndpoint();
if(endpointURI==null){
return null;
}
final String uri = endpointURI.getString();
try {
return FederatedQueryWithSucceedingJoin.addEndpointVariable((Variable)endpoint, endpointURI, Client.submitQuery(uri, fQuery, bindingsFactory)).oneTimeIterator();
} catch (final IOException e) {
System.err.println(e);
e.printStackTrace();
}
return null;
}
private URILiteral nextEndpoint(){
while(this.it.hasNext()){
final Bindings service = this.it.next();
Literal endpointURI = service.get((Variable) endpoint);
if (endpointURI instanceof LazyLiteral) {
endpointURI = ((LazyLiteral) endpointURI).getLiteral();
}
if (endpointURI instanceof URILiteral) {
final URILiteral result = (URILiteral) endpointURI;
if(!this.alreadyAskedEndpoints.contains(result)){ // do not ask endpoints several times!
this.alreadyAskedEndpoints.add(result);
return result;
}
} else {
// error message or maybe ignore?
}
}
return null;
}
});
}
return null;
}
protected abstract String toStringQuery(QueryResult bindings);
public static QueryResult addEndpointVariable(final Variable endpointVariable, final Literal endpointURI, final QueryResult resultSetToBindingsList) {
return QueryResult.createInstance(new ParallelIterator<Bindings>(){
private final Iterator<Bindings> it = resultSetToBindingsList.oneTimeIterator();
@Override
public boolean hasNext() {
return this.it.hasNext();
}
@Override
public Bindings next() {
final Bindings bindings = this.it.next();
if(bindings==null){
return null;
}
bindings.add(endpointVariable, endpointURI);
return bindings;
}
@Override
public void remove() {
this.it.remove();
}
@Override
public void close() {
if(this.it instanceof ParallelIterator){
((ParallelIterator<Bindings>)this.it).close();
}
}
});
}
}