extensions/indexing-sql/src/main/java/org/apache/zest/index/sql/support/common/RebuildingStrategy.java

/*
 * Copyright (c) 2010, Stanislav Muhametsin. All Rights Reserved.
 *
 * 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.apache.zest.index.sql.support.common;

/**
 * Helper interface to let the user of SQL-Indexing decide when to re-build SQL schema. Rebuilding
 * means first deleting all tables that are going to be used, and then creating them. Useful for
 * tests or when your app is in dev mode.
 *
 * You can decide your application's re-building policy for example like this:
 * {@code mainModule.addServices(RebuildingStrategy.class).withMixins(RebuildingStrategy.AlwaysNeed.class);}
 * . This way your application will always re-build all index data at startup.
 */
public interface RebuildingStrategy
{
    boolean rebuildingRequired( String dbAppVersion, String currentAppVersion );

    /**
     * The re-building strategy which ALWAYS re-builds the database schema. Useful with tests and
     * during early development stage of application.
     */
    public class AlwaysNeed
        implements RebuildingStrategy
    {
        @Override
        public boolean rebuildingRequired( String dbAppVersion, String currentAppVersion )
        {
            return true;
        }
    }

    /**
     * The re-building strategy which NEVER re-builds the database schema. Useful when current
     * Zest-related database schema structure must be preserved at all costs.
     */
    public class NeverNeed
        implements RebuildingStrategy
    {
        @Override
        public boolean rebuildingRequired( String dbAppVersion, String currentAppVersion )
        {
            return false;
        }
    }

    /**
     * The re-building strategy, which re-builds everything when application version changes. Useful
     * when migration from versions is implemented, or when application structure changes along with
     * version (but not during same version).
     */
    public class NeedOnChange
        implements RebuildingStrategy
    {
        @Override
        public boolean rebuildingRequired( String dbAppVersion, String currentAppVersion )
        {
            return !dbAppVersion.equals( currentAppVersion );
        }
    }

}