ORDIVariableBinding.java

/*
   This file is part of the LarKC platform 
   http://www.larkc.eu/

   Copyright 2010 LarKC project consortium

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
 */
package eu.larkc.core.query;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;

import org.openrdf.model.Value;
import org.openrdf.query.BindingSet;
import org.openrdf.query.TupleQueryResultHandler;
import org.openrdf.query.TupleQueryResultHandlerException;

import eu.larkc.core.data.CloseableIterator;
import eu.larkc.core.data.iterator.SimpleCloseableIterator;

/**
 * ORDIVariableBinding implements asynchronous RDF solution result reading from
 * Sesame enabled SPARQL query engine.
 * 
 * @author vassil
 * 
 */
public class ORDIVariableBinding extends VariableBindingBase implements
		TupleQueryResultHandler {

	private final static long serialVersionUID = 1L;

	public synchronized void startQueryResult(List<String> list) {
		bindNames = list.toArray(new String[list.size()]);
		super.notifyAll();
	}

	public void endQueryResult() {
		while (true) {
			try {
				results.put(new FinalBindingSet());
				return;
			} catch (InterruptedException ie) {
			}
		}
	}

	public void handleSolution(BindingSet bindingset)
			throws TupleQueryResultHandlerException {
		if (isClosed.get()) {
			throw new TupleQueryResultHandlerException("Closed!");
		}
		while (true) {
			try {
				results.put(bindingset);
				return;
			} catch (InterruptedException ie) {
			}
		}
	}

	// Custom serialization methods
	private void writeObject(ObjectOutputStream out) throws IOException {
		CloseableIterator<Binding> i = iterator();
		// used to wait until the bindNames field is init
		getVariables();
		out.writeObject(bindNames);
		out.writeBoolean(i.hasNext());
		while (i.hasNext()) {
			out.writeObject(i.next().getValues());
			out.writeBoolean(i.hasNext());
		}
		out.flush();
		isClosed.set(true);
	}

	@SuppressWarnings("unchecked")
	private void readObject(ObjectInputStream in) throws IOException,
			ClassNotFoundException {
		bindNames = (String[]) in.readObject();
		List<Binding> data = new ArrayList<Binding>();
		while (in.readBoolean()) {
			List<Value> vals = (List<Value>) in.readObject();
			data.add(new WrappedBinding(vals));
		}
		iterator = new SimpleCloseableIterator<Binding>(data.iterator());
	}
}