UUIDPIDGenerator.java

/**
 * Copyright 2008 The University of North Carolina at Chapel Hill
 *
 * 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 edu.unc.lib.dl.pidgen;

import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

import edu.unc.lib.dl.fedora.PID;
import edu.unc.lib.dl.util.TripleStoreQueryService;

/**
 * PIDGenerator that uses the Java UUID class to generate type 4 UUID-based PIDs.
 * 
 * @see http://www.ietf.org/rfc/rfc4122.txt This identifier scheme is compatible with both the Fedora PID and a URN.
 *      PIDs are of the form "uuid:21a579fb-7bca-4025-88c0-345ee293725b". Note that datastream PIDs and datastream
 *      version PIDs will be uniquely persistent, but will not be compatible with URN.
 */
public class UUIDPIDGenerator implements PIDGenerator {
	private TripleStoreQueryService tripleStoreQueryService;
	private boolean verifyUnique = false;

	public boolean isVerifyUnique() {
		return verifyUnique;
	}

	public void init() {
		if (this.verifyUnique) {
			if (this.tripleStoreQueryService == null) {
				throw new Error("The UUIDPIDGenerator cannot verify unique PIDs without a tripleStoreQueryService.");
			}
		}
	}

	public void setVerifyUnique(boolean verifyUnique) {
		this.verifyUnique = verifyUnique;
	}

	public TripleStoreQueryService getTripleStoreQueryService() {
		return tripleStoreQueryService;
	}

	public void setTripleStoreQueryService(TripleStoreQueryService tripleStoreQueryService) {
		this.tripleStoreQueryService = tripleStoreQueryService;
	}

	public UUIDPIDGenerator() {
	}

	public PID getNextPID() {
		return getNextPIDs(1).get(0);
	}

	public List<PID> getNextPIDs(int howMany) {
		List<PID> result = new ArrayList<PID>();
		for (int i = 0; i < howMany; i++) {
			while (true) {
				UUID u = UUID.randomUUID();
				String s = String.format("uuid:%1$s", u);
				PID p = new PID(s);
				if (this.verifyUnique) {
					if (this.tripleStoreQueryService.verify(p) != null) {
						continue;
					}
				}
				result.add(p);
				break;
			}
		}
		return result;
	}

}