sequenceidgenerator.java

torque服务器源代码

package org.apache.torque.oid;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Turbine" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
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 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Turbine", nor may "Apache" appear in their name, without
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import java.math.BigDecimal;
import java.sql.Connection;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.apache.torque.adapter.DB;

import com.workingdogs.village.QueryDataSet;
import com.workingdogs.village.Record;
import com.workingdogs.village.Value;

/**
 * This generator works with databases that have an sql syntax for
 * getting an id prior to inserting a row into the database.
 *
 * @author <a href="mailto:[e-mail]">John D. McNally</a>
 * @version $Id: SequenceIdGenerator.java,v 1.10 2003/08/25 16:33:22 henning Exp $
 */
public class SequenceIdGenerator implements IdGenerator
{
    /** The log. */
    private static Log log = LogFactory.getLog(SequenceIdGenerator.class);

    /** the adapter that knows the correct sql syntax */
    private DB dbAdapter;

    /**
     * Creates an IdGenerator which will work with the specified database.
     *
     * @param adapter the adapter that knows the correct sql syntax.
     */
    public SequenceIdGenerator(DB adapter)
    {
        dbAdapter = adapter;
    }

    /**
     * Retrieves an id as an int.
     *
     * @param connection A Connection.
     * @param keyInfo an Object that contains additional info.
     * @return An int with the value for the id.
     * @exception Exception Database error.
     */
    public int getIdAsInt(Connection connection, Object keyInfo)
        throws Exception
    {
        return getIdAsVillageValue(connection, keyInfo).asInt();
    }

    /**
     * Retrieves an id as an long.
     *
     * @param connection A Connection.
     * @param keyInfo an Object that contains additional info.
     * @return A long with the value for the id.
     * @exception Exception Database error.
     */
    public long getIdAsLong(Connection connection, Object keyInfo)
        throws Exception
    {
        return getIdAsVillageValue(connection, keyInfo).asLong();
    }

    /**
     * Retrieves an id as a BigDecimal.
     *
     * @param connection A Connection.
     * @param keyInfo an Object that contains additional info.
     * @return A BigDecimal id
     * @exception Exception Database error.
     */
    public BigDecimal getIdAsBigDecimal(Connection connection, Object keyInfo)
        throws Exception
    {
        return getIdAsVillageValue(connection, keyInfo).asBigDecimal();
    }

    /**
     * Retrieves an id as an String.
     *
     * @param connection A Connection.
     * @param keyInfo an Object that contains additional info.
     * @return A String id
     * @exception Exception Database error.
     */
    public String getIdAsString(Connection connection, Object keyInfo)
        throws Exception
    {
        return getIdAsVillageValue(connection, keyInfo).asString();
    }

    /**
     * A flag to determine the timing of the id generation
     *
     * @return a <code>boolean</code> value
     */
    public boolean isPriorToInsert()
    {
        return true;
    }

    /**
     * A flag to determine the timing of the id generation
     *
     * @return a <code>boolean</code> value
     */
    public boolean isPostInsert()
    {
        return false;
    }

    /**
     * A flag to determine whether a Connection is required to
     * generate an id.
     *
     * @return a <code>boolean</code> value
     */
    public boolean isConnectionRequired()
    {
        return true;
    }

    /**
     * Retrieves an id as a Village Value.
     *
     * @param connection A Connection.
     * @param keyInfo an Object that contains additional info.
     * @return A Village Value id.
     * @exception Exception Database error.
     */
    private Value getIdAsVillageValue(Connection connection, Object keyInfo)
        throws Exception
    {
        String idSql = dbAdapter.getIDMethodSQL(keyInfo);
        if (log.isDebugEnabled())
        {
            log.debug(idSql);
        }

        // Execute the query.
        QueryDataSet qds = new QueryDataSet(connection, idSql);
        Record rec;
        try
        {
            qds.fetchRecords(1);
            rec = qds.getRecord(0);  // Records are 0 based.
        }
        finally
        {
            if (qds != null)
            {
                qds.close();
            }
        }
        return rec.getValue(1); // Values are 1 based.
    }
}