src/java/org/apache/ddlutils/task/WriteSchemaSqlToFileCommand.java

package org.apache.ddlutils.task;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;

import org.apache.ddlutils.Platform;
import org.apache.ddlutils.model.Database;
import org.apache.ddlutils.platform.CreationParameters;
import org.apache.tools.ant.BuildException;

/**
 * Parses the schema XML files specified in the enclosing task, and writes the SQL statements
 * necessary to create this schema in the database, to a file. Note that this SQL is
 * database specific and hence this subtask requires that for the enclosing task, either a
 * data source is specified (via the <code>database</code> sub element) or the
 * <code>databaseType</code> attribute is used to specify the database type.
 * 
 * @version $Revision: 289996 $
 * @ant.task name="writeSchemaSqlToFile"
 */
public class WriteSchemaSqlToFileCommand extends DatabaseCommandWithCreationParameters
{
    /** The file to output the DTD to. */
    private File _outputFile;
    /** Whether to alter or re-set the database if it already exists. */
    private boolean _alterDb = true;
    /** Whether to drop tables and the associated constraints if necessary. */
    private boolean _doDrops = true;

    /**
     * Specifies the name of the file to write the SQL commands to.
     * 
     * @param outputFile The output file
     * @ant.required
     */
    public void setOutputFile(File outputFile)
    {
        _outputFile = outputFile;
    }

    /**
     * Determines whether to alter the database if it already exists, or re-set it.
     * 
     * @return <code>true</code> if to alter the database
     */
    protected boolean isAlterDatabase()
    {
        return _alterDb;
    }

    /**
     * Specifies whether DdlUtils shall generate SQL to alter an existing database rather
     * than SQL for clearing it and creating it new.
     * 
     * @param alterTheDb <code>true</code> if SQL to alter the database shall be created
     * @ant.not-required Per default SQL for altering the database is created
     */
    public void setAlterDatabase(boolean alterTheDb)
    {
        _alterDb = alterTheDb;
    }

    /**
     * Determines whether SQL is generated to drop tables and the associated constraints
     * if necessary.
     * 
     * @return <code>true</code> if drops SQL shall be generated if necessary
     */
    protected boolean isDoDrops()
    {
        return _doDrops;
    }

    /**
     * Specifies whether SQL for dropping tables, external constraints, etc. is created if necessary.
     * Note that this is only relevant when <code>alterDatabase</code> is <code>false</code>.
     * 
     * @param doDrops <code>true</code> if drops shall be performed if necessary
     * @ant.not-required Per default, drop SQL statements are created
     */
    public void setDoDrops(boolean doDrops)
    {
        _doDrops = doDrops;
    }

    /**
     * {@inheritDoc}
     */
    public void execute(DatabaseTaskBase task, Database model) throws BuildException
    {
        if (_outputFile == null)
        {
            throw new BuildException("No output file specified");
        }
        if (_outputFile.exists() && !_outputFile.canWrite())
        {
            throw new BuildException("Cannot overwrite output file "+_outputFile.getAbsolutePath());
        }

        Platform           platform        = getPlatform();
        boolean            isCaseSensitive = platform.isDelimitedIdentifierModeOn();
        CreationParameters params          = getFilteredParameters(model, platform.getName(), isCaseSensitive);
        FileWriter         writer          = null;

        try
        {
            writer = new FileWriter(_outputFile);

            platform.setScriptModeOn(true);
            if (platform.getPlatformInfo().isSqlCommentsSupported())
            {
                // we're generating SQL comments if possible
                platform.setSqlCommentsOn(true);
            }

            boolean shouldAlter = isAlterDatabase();

            if (shouldAlter)
            {
                if (getDataSource() == null)
                {
                    shouldAlter = false;
                    _log.warn("Cannot alter the database because no database connection was specified." +
                              " SQL for database creation will be generated instead.");
                }
                else
                {
                    try
                    {
                        Connection connection = getDataSource().getConnection();

                        connection.close();
                    }
                    catch (SQLException ex)
                    {
                        shouldAlter = false;
                        _log.warn("Could not establish a connection to the specified database, " +
                                  "so SQL for database creation will be generated instead.",
                                  ex);
                    }
                }
            }
            if (shouldAlter)
            {
                Database currentModel = (getCatalogPattern() != null) || (getSchemaPattern() != null) ?
                                             platform.readModelFromDatabase("unnamed", getCatalogPattern(), getSchemaPattern(), null) :
                                             platform.readModelFromDatabase("unnamed");

                writer.write(platform.getAlterModelSql(currentModel, model, params));
            }
            else
            {
                writer.write(platform.getCreateModelSql(model, params, _doDrops, !isFailOnError()));
            }
            _log.info("Written schema SQL to " + _outputFile.getAbsolutePath());
        }
        catch (Exception ex)
        {
            handleException(ex, ex.getMessage());
        }
        finally
        {
            if (writer != null)
            {
                try
                {
                    writer.close();
                }
                catch (IOException ex)
                {
                    _log.error("Could not close file " + _outputFile.getAbsolutePath(), ex);
                }
            }
        }
    }
}