idgeneratorfactory.java

另外一种持久性o/m软件

package org.apache.torque.oid;

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * 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.
 */

import org.apache.torque.adapter.DB;
import org.apache.torque.adapter.IDMethod;

/**
 * A factory which instantiates {@link
 * org.apache.torque.oid.IdGenerator} implementations.
 *
 * @author <a href="mailto:[e-mail]">Daniel Rall</a>
 * @version $Id: IDGeneratorFactory.java,v 1.4 2005/01/31 19:43:53 tfischer Exp $
 */
public class IDGeneratorFactory
{
    /**
     * The list of ID generation method types which have associated
     * {@link org.apache.torque.oid.IdGenerator} implementations.
     */
    public static final String[] ID_GENERATOR_METHODS =
    {
        IDMethod.NATIVE, IDMethod.AUTO_INCREMENT, IDMethod.SEQUENCE
    };

    /**
     * Factory method which instantiates {@link
     * org.apache.torque.oid.IdGenerator} implementations based on the
     * return value of the provided adapter's {@link
     * org.apache.torque.adapter.DB#getIDMethodType()} method.
     * Returns <code>null</code> for unknown types.
     *
     * @param dbAdapter The type of adapter to create an ID generator for.
     * @return The appropriate ID generator (possibly <code>null</code>).
     */
    public static IdGenerator create(DB dbAdapter, String name)
    {
        String idMethod = dbAdapter.getIDMethodType();
        if (IDMethod.AUTO_INCREMENT.equals(idMethod))
        {
            return new AutoIncrementIdGenerator(dbAdapter, name);
        }
        else if (IDMethod.SEQUENCE.equals(idMethod))
        {
            return new SequenceIdGenerator(dbAdapter, name);
        }
        else
        {
            return null;
        }
    }
}