RdfGraphDataSet.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.data;

import org.openrdf.model.Statement;
import org.openrdf.model.URI;
import org.openrdf.model.impl.ContextStatementImpl;

import eu.larkc.core.query.SPARQLQuery;
import eu.larkc.core.query.SPARQLQueryImpl;

/**
 * @author vassil
 */
public class RdfGraphDataSet extends RdfGraphBase {

	private static final long serialVersionUID = 1L;
	private final SPARQLEndpoint endpoint;
	private long timeStamp = System.currentTimeMillis();

	/**
	 * Constructor
	 * 
	 * @param graph
	 *            is the named of the named graph
	 * @param endpoint
	 *            is endpoint which serves this named graph
	 */
	public RdfGraphDataSet(URI graph, SPARQLEndpoint endpoint) {
		super(graph);
		if (endpoint == null) {
			throw new IllegalArgumentException("null!");
		}
		this.endpoint = endpoint;
	}

	public CloseableIterator<Statement> getStatements() {
		String q = String.format(
				"construct {?s ?p ?o} FROM <%s> WHERE {?s ?p ?o}", getName());
		SPARQLQuery query = new SPARQLQueryImpl(q);
		CloseableIterator<Statement> inner = endpoint.executeConstruct(query)
				.getStatements();
		return new GraphCloseableIterator(getName(), inner);
	}

	public boolean equals(Object o) {
		if (o instanceof RdfGraphDataSet == false) {
			return false;
		}
		if (getName().toString().equals(
				((RdfGraphDataSet) o).getName().toString()) == false) {
			return false;
		}
		if (Math.abs(timeStamp - (((RdfGraphDataSet) o).timeStamp)) > DataFactoryImpl.REFERENCE_TYPES_CACHE_TIME) {
			return false;
		}
		return true;
	}

	public int hashCode() {
		// the mutable hashcodes are risky (timeStamp)
		return getName().toString().hashCode();
	}

	/**
	 * @author vassil
	 */
	public class GraphCloseableIterator implements CloseableIterator<Statement> {

		private URI graph;
		private CloseableIterator<Statement> inner;

		/**
		 * Constructor
		 * 
		 * @param graph
		 * @param inner
		 */
		public GraphCloseableIterator(URI graph,
				CloseableIterator<Statement> inner) {
			if (inner == null || graph == null) {
				throw new IllegalArgumentException();
			}
			this.graph = graph;
			this.inner = inner;
		}

		public boolean hasNext() {
			return inner.hasNext();
		}

		public Statement next() {
			Statement s = inner.next();
			return new ContextStatementImpl(s.getSubject(), s.getPredicate(), s
					.getObject(), graph);
		}

		public void remove() {
			inner.remove();
		}

		public void close() {
			inner.close();
		}

		public boolean isClosed() {
			return inner.isClosed();
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * eu.larkc.core.data.InformationSet#toRDF(eu.larkc.core.data.SetOfStatements
	 * )
	 */
	@Override
	public SetOfStatements toRDF(SetOfStatements data) {
		throw new RuntimeException("Not implemented!");
	}
}