/* * Copyright 2004-2006 OpenSymphony * * 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 org.quartz.impl.jdbcjobstore;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.SQLException;/** * Provide thread/resource locking in order to protect * resources from being altered by multiple threads at the same time using * a db row update. *  * <p> * <b>Note:</b> This Semaphore implementation is useful for databases that do * not support row locking via "SELECT FOR UPDATE" type syntax, for example * Microsoft SQLServer (MSSQL). * </p>  */public class UpdateLockRowSemaphore extends DBSemaphore {    /*     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     *     * Constants.     *     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     */    public static final String UPDATE_FOR_LOCK =         "UPDATE " + TABLE_PREFIX_SUBST + TABLE_LOCKS +         " SET " + COL_LOCK_NAME + " = " + COL_LOCK_NAME +        " WHERE " + COL_LOCK_NAME + " = ? ";    /*     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     *     * Constructors.     *     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     */    public UpdateLockRowSemaphore() {        super(DEFAULT_TABLE_PREFIX, null, UPDATE_FOR_LOCK);    }    /*     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     *     * Interface.     *     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     */    /**     * Execute the SQL select for update that will lock the proper database row.     */    protected void executeSQL(Connection conn, String lockName, String expandedSQL) throws LockException {        PreparedStatement ps = null;        try {            ps = conn.prepareStatement(expandedSQL);            ps.setString(1, lockName);            if (getLog().isDebugEnabled()) {                getLog().debug(                    "Lock '" + lockName + "' is being obtained: " +                     Thread.currentThread().getName());            }                        int numUpdate = ps.executeUpdate();                        if (numUpdate < 1) {                throw new SQLException(Util.rtp(                    "No row exists in table " + TABLE_PREFIX_SUBST + TABLE_LOCKS +                     " for lock named: " + lockName, getTablePrefix()));            }        } catch (SQLException sqle) {            //Exception src =            // (Exception)getThreadLocksObtainer().get(lockName);            //if(src != null)            //  src.printStackTrace();            //else            //  System.err.println("--- ***************** NO OBTAINER!");            if(getLog().isDebugEnabled()) {                getLog().debug(                    "Lock '" + lockName + "' was not obtained by: " +                     Thread.currentThread().getName());            }                        throw new LockException(                "Failure obtaining db row lock: " + sqle.getMessage(), sqle);        } finally {            if (ps != null) {                try {                    ps.close();                } catch (Exception ignore) {                }            }        }    }        protected String getUpdateLockRowSQL() {        return getSQL();    }    public void setUpdateLockRowSQL(String updateLockRowSQL) {        setSQL(updateLockRowSQL);    }}