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A federation engine for virtually integrating SPARQL endpoints

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/*******************************************************************************
 * Copyright (c) 2019 Eclipse RDF4J contributors.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Distribution License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *******************************************************************************/
package org.eclipse.rdf4j.federated.write;

import org.eclipse.rdf4j.common.transaction.TransactionSetting;
import org.eclipse.rdf4j.model.IRI;
import org.eclipse.rdf4j.model.Resource;
import org.eclipse.rdf4j.model.Value;
import org.eclipse.rdf4j.repository.Repository;
import org.eclipse.rdf4j.repository.RepositoryConnection;
import org.eclipse.rdf4j.repository.RepositoryException;

/**
 * A {@link WriteStrategy} to write to a designated {@link Repository}. This write strategy opens a fresh
 * {@link RepositoryConnection} and keeps this until a call of {@link #close()}.
 *
 *
 * 
 * Note: this is an experimental feature which is subject to change in a future version.
 * 
 *
 * @author Andreas Schwarte
 * @see WriteStrategy
 */
public class RepositoryWriteStrategy implements WriteStrategy {

	private final Repository writeRepository;

	private RepositoryConnection connection = null;

	private TransactionSetting[] transactionSettings;

	public RepositoryWriteStrategy(Repository writeRepository) {
		super();
		this.writeRepository = writeRepository;
	}

	@Override
	public void close() throws RepositoryException {
		if (connection != null) {
			connection.close();
		}
	}

	@Override
	public void begin() throws RepositoryException {
		createConnection();
		if (transactionSettings != null && transactionSettings.length > 0) {
			connection.begin(transactionSettings);
		} else {
			connection.begin();
		}
	}

	@Override
	public void commit() throws RepositoryException {
		createConnection();
		connection.commit();
	}

	@Override
	public void rollback() throws RepositoryException {
		createConnection();
		connection.rollback();
	}

	@Override
	public void addStatement(Resource subj, IRI pred, Value obj,
			Resource... contexts) throws RepositoryException {
		createConnection();
		connection.add(subj, pred, obj, contexts);
	}

	@Override
	public void removeStatement(Resource subj, IRI pred, Value obj,
			Resource... contexts) throws RepositoryException {
		createConnection();
		connection.remove(subj, pred, obj, contexts);
	}

	@Override
	public void clear(Resource... contexts) throws RepositoryException {
		createConnection();
		connection.clear(contexts);
	}

	private void createConnection() throws RepositoryException {
		if (connection == null || !connection.isOpen()) {
			connection = writeRepository.getConnection();
		}
	}

	@Override
	public void clearNamespaces() throws RepositoryException {
		createConnection();
		connection.clearNamespaces();
	}

	@Override
	public void setTransactionSettings(TransactionSetting... transactionSettings) throws RepositoryException {
		this.transactionSettings = transactionSettings;
	}
}