com.flexive.core.storage.MySQL.MySQLHierarchicalStorage.java Source code

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Here is the source code for com.flexive.core.storage.MySQL.MySQLHierarchicalStorage.java

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/***************************************************************
 *  This file is part of the [fleXive](R) framework.
 *
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 *  UCS - unique computing solutions gmbh (http://www.ucs.at)
 *  All rights reserved
 *
 *  The [fleXive](R) project is free software; you can redistribute
 *  it and/or modify it under the terms of the GNU Lesser General Public
 *  License version 2.1 or higher as published by the Free Software Foundation.
 *
 *  The GNU Lesser General Public License can be found at
 *  http://www.gnu.org/licenses/lgpl.html.
 *  A copy is found in the textfile LGPL.txt and important notices to the
 *  license from the author are found in LICENSE.txt distributed with
 *  these libraries.
 *
 *  This library 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.
 *
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 *  please see the company website: http://www.ucs.at
 *
 *  For further information about [fleXive](R), please see the
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package com.flexive.core.storage.MySQL;

import com.flexive.core.Database;
import com.flexive.core.DatabaseConst;
import com.flexive.core.storage.ContentStorage;
import com.flexive.core.storage.DBStorage;
import com.flexive.core.storage.StorageManager;
import com.flexive.core.storage.genericSQL.GenericBinarySQLStorage;
import com.flexive.core.storage.genericSQL.GenericHierarchicalStorage;
import com.flexive.shared.exceptions.FxDbException;
import com.flexive.shared.exceptions.FxRuntimeException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
 * MySQL implementation of hierarchical content handling
 *
 * @author Markus Plesser (markus.plesser@flexive.com), UCS - unique computing solutions gmbh (http://www.ucs.at)
 */
public class MySQLHierarchicalStorage extends GenericHierarchicalStorage {

    private static final Log LOG = LogFactory.getLog(MySQLHierarchicalStorage.class);

    private static final MySQLHierarchicalStorage instance = new MySQLHierarchicalStorage();

    /**
     * Ctor
     */
    public MySQLHierarchicalStorage() {
        super(new GenericBinarySQLStorage());
    }

    /**
     * Singleton getter
     *
     * @return ContentStorage
     */
    public static ContentStorage getInstance() {
        return instance;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void lockTables(Connection con, long id, int version) throws FxRuntimeException {
        int counter = 0;
        while (!tryLock(con, id, version)) {
            if (LOG.isInfoEnabled()) {
                LOG.info("Failed to lock content tables, waiting 100ms and retrying... (try #" + (++counter) + ")");
            }
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                // ignore
            }
        }
        if (counter > 0)
            LOG.info("Locking succeeded without (dead)locks after " + counter + " tries!");
    }

    protected boolean tryLock(Connection con, long id, int version) {
        try {
            PreparedStatement ps = null;
            try {
                //grouping by (dummy) 1 prevents reading the data and just issues the lock
                String ver = (version <= 0 ? "" : " AND VER=?") + " GROUP BY 1";
                final String LOCK_MODE = " FOR UPDATE";
                //see: http://dev.mysql.com/doc/refman/5.1/en/innodb-deadlocks.html
                //and http://dev.mysql.com/doc/refman/5.1/en/innodb-locking-reads.html
                //                final String LOCK_MODE = " LOCK IN SHARE MODE";
                ps = con.prepareStatement(
                        "SELECT 1 FROM " + DatabaseConst.TBL_CONTENT + " WHERE ID=?" + ver + LOCK_MODE);
                ps.setLong(1, id);
                if (version > 0)
                    ps.setInt(2, version);
                ps.executeQuery();
                ps.close();
                ps = con.prepareStatement(
                        "SELECT 1 FROM " + DatabaseConst.TBL_CONTENT_DATA + " WHERE ID=?" + ver + LOCK_MODE);
                ps.setLong(1, id);
                if (version > 0)
                    ps.setInt(2, version);
                ps.executeQuery();
                ps.close();
                /*ps = con.prepareStatement("SELECT 1 FROM " + DatabaseConst.TBL_CONTENT_BINARY + " WHERE ID=?" + ver + LOCK_MODE);
                ps.setLong(1, id);
                if (version > 0) ps.setInt(2, version);
                ps.executeQuery();*/
                //fulltext table uses MyISAM engine and can not be locked
            } finally {
                Database.closeObjects(MySQLHierarchicalStorage.class, null, ps);
            }
            if (LOG.isDebugEnabled())
                LOG.debug("Locked instances of id #" + id
                        + (version > 0 ? " and version #" + version : " (all versions)"));
            return true;
        } catch (SQLException e) {
            final DBStorage si = StorageManager.getStorageImpl();
            if (si.isDeadlock(e) || si.isQueryTimeout(e)) {
                //                if (LOG.isDebugEnabled()) {
                LOG.warn("Possible (dead)lock detected while locking content tables.");
                //                }
                return false;
            } else {
                //noinspection ThrowableInstanceNeverThrown
                throw new FxDbException(LOG, e, "ex.db.sqlError", e.getMessage()).asRuntimeException();
            }
        }
    }
}