podd.dataaccess.hibernate.HibernateFedoraPIDGenerator.java Source code

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Here is the source code for podd.dataaccess.hibernate.HibernateFedoraPIDGenerator.java

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/*
 * Copyright (c) 2009 - 2010. School of Information Technology and Electrical
 * Engineering, The University of Queensland.  This software is being developed
 * for the "Phenomics Ontoogy Driven Data Management Project (PODD)" project.
 * PODD is a National e-Research Architecture Taskforce (NeAT) project
 * co-funded by ANDS and ARCS.
 *
 * PODD is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * PODD is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PODD.  If not, see <http://www.gnu.org/licenses/>.
 */

package podd.dataaccess.hibernate;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.hibernate.HibernateException;
import org.hibernate.SQLQuery;
import org.hibernate.Session;

import podd.exception.DataAccessException;
import podd.util.db.HibernateSessionFactory;
import podd.util.fedora.PIDGenerator;

/**
 * @author Yuan-Fang Li
 * @version $Id$
 */

public class HibernateFedoraPIDGenerator implements PIDGenerator {
    private final static Logger LOGGER = LoggerFactory.getLogger(HibernateFedoraPIDGenerator.class);
    private static final boolean _INFO = LOGGER.isInfoEnabled();

    private String pidTableName;
    private HibernateSessionFactory factory;

    public HibernateFedoraPIDGenerator(HibernateSessionFactory factory, String pidTableName) {
        this.factory = factory;
        this.pidTableName = pidTableName;
    }

    @Override
    // FIXME: TODO YF: This method executed concurrently will sometimes return stale values!
    public synchronized String getNextPID(String namespace) throws DataAccessException {
        long start = System.currentTimeMillis();

        try {
            Session session = factory.currentSession();
            session.beginTransaction();
            try {
                SQLQuery sqlQuery = createSelectIDSQLQuery(namespace, session);
                Integer currentPid = (Integer) sqlQuery.uniqueResult();
                if (null == currentPid) {
                    currentPid = 0;
                    sqlQuery = createInsertSQLQuery(namespace, session);
                } else {
                    currentPid++;
                    sqlQuery = createUpdateIDSQLQuery(namespace, session, currentPid);
                }
                sqlQuery.executeUpdate();
                session.getTransaction().commit();
                return namespace + ":" + currentPid.toString();
            } catch (Exception e) {
                session.getTransaction().rollback();
                throw new DataAccessException(e);
            } finally {
                session.flush();
                factory.closeSession();
            }
        } finally {
            if (_INFO) {
                long end = System.currentTimeMillis();
                LOGGER.info("getNextPID timing=" + (end - start));
            }
        }
    }

    public String removeNamespace(String namespace) throws DataAccessException {
        Session session = factory.currentSession();
        try {
            session.beginTransaction();
            SQLQuery selectQuery = createSelectIDSQLQuery(namespace, session);
            Integer currentPid = (Integer) selectQuery.uniqueResult();
            if (null != currentPid) {
                SQLQuery deleteQuery = createDeleteSQLQuery(namespace, session);
                deleteQuery.executeUpdate();
            }
            session.getTransaction().commit();
            return null == currentPid ? null : namespace + ":" + currentPid;
        } catch (HibernateException e) {
            session.getTransaction().rollback();
            throw new DataAccessException(e);
        } finally {
            factory.closeSession();
        }
    }

    private SQLQuery createInsertSQLQuery(String namespace, Session session) {
        final String sqlQueryString = "insert into " + pidTableName + " (namespace, highestID) values ('"
                + namespace + "', 1)";
        return session.createSQLQuery(sqlQueryString);
    }

    private SQLQuery createUpdateIDSQLQuery(String namespace, Session session, Integer newPid) {
        final String sqlQueryString = "update " + pidTableName + " set highestID=" + newPid + " where namespace='"
                + namespace + "'";
        return session.createSQLQuery(sqlQueryString);
    }

    private SQLQuery createSelectIDSQLQuery(String namespace, Session session) {
        String sqlQueryString = "select highestID FROM " + pidTableName + " where namespace='" + namespace + "'";
        return session.createSQLQuery(sqlQueryString);
    }

    private SQLQuery createDeleteSQLQuery(String namespace, Session session) {
        String deleteQueryString = "delete from " + pidTableName + " where namespace='" + namespace + "'";
        return session.createSQLQuery(deleteQueryString);
    }
}