org.acmsl.queryj.tools.handlers.DatabaseMetaDataCacheReadingHandler.java Source code

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Here is the source code for org.acmsl.queryj.tools.handlers.DatabaseMetaDataCacheReadingHandler.java

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/*
                    QueryJ Core
    
Copyright (C) 2002-today  Jose San Leandro Armendariz
                          chous@acm-sl.org
    
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or any later version.
    
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.
    
You should have received a copy of the GNU General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    
Thanks to ACM S.L. for distributing this library under the GPL license.
Contact info: jose.sanleandro@acm-sl.com
    
 ******************************************************************************
 *
 * Filename: DatabaseMetaDataCacheReadingHandler.java
 *
 * Author: Jose San Leandro Armendariz
 *
 * Description: Checks whether we can use the cached metadata or not.
 *
 */
package org.acmsl.queryj.tools.handlers;

/*
 * Importing some project classes.
 */
import org.acmsl.queryj.QueryJCommand;
import org.acmsl.queryj.api.exceptions.QueryJException;
import org.acmsl.queryj.metadata.MetadataManager;
import org.acmsl.queryj.metadata.vo.Attribute;
import org.acmsl.queryj.metadata.vo.Table;
import org.acmsl.queryj.api.exceptions.QueryJBuildException;

/*
 * Importing some ACM-SL Commons.
 */
import org.acmsl.commons.logging.UniqueLogFactory;

/*
 * Importing some Apache Commons-Logging classes.
 */
import org.apache.commons.logging.Log;

/*
 * Importing JetBrains annotations.
 */
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

/*
 * Importing some JDK classes.
 */
import java.sql.DatabaseMetaData;
import java.sql.SQLException;
import java.util.List;

/*
 * Importing checkthread.org annotations.
 */
import org.checkthread.annotations.ThreadSafe;

/**
 * Checks whether we can use the cached metadata or not.
 * @author <a href="mailto:chous@acm-sl.org">Jose San Leandro Armendariz</a>
 * @since 3.0
 */
@ThreadSafe
public class DatabaseMetaDataCacheReadingHandler extends AbstractDatabaseMetaDataCacheHandler {
    /**
     * String literal: "Cannot extract table metadata"
     */
    protected static final String CANNOT_EXTRACT_TABLE_METADATA_LITERAL = "Cannot extract table metadata";

    /**
     * Handles given parameters.
     * @param parameters the parameters to handle.
     * @param alreadyDone the flag indicating whether the metadata
     * extraction has already been done.
     * @param metaData the database metadata.
     * @return <code>true</code> if the chain should be stopped.
     */
    @Override
    protected boolean handle(@NotNull final QueryJCommand parameters, final boolean alreadyDone,
            @NotNull final DatabaseMetaData metaData) throws QueryJBuildException {
        boolean result = false;

        if (!alreadyDone) {
            result = super.handle(parameters, false, metaData);
        }

        return result;
    }

    /**
     * Checks whether the database vendor matches this handler.
     * @param productName the product name.
     * @param productVersion the product version.
     * @param majorVersion the major version number.
     * @param minorVersion the minor version number.
     * @return <code>true</code> in case it matches.
     */
    @Override
    protected boolean checkVendor(@NotNull final String productName, @NotNull final String productVersion,
            final int majorVersion, final int minorVersion) {
        return true;
    }

    /**
     * Handles given parameters.
     * @param parameters the parameters to handle.
     * @param metadataManager the {@link MetadataManager} instance.
     * @return <code>true</code> if the chain should be stopped.
     */
    @Override
    protected boolean handle(@NotNull final QueryJCommand parameters,
            @Nullable final MetadataManager metadataManager) throws QueryJBuildException {
        boolean result = false;

        // We only need the table names, if they're not extracted already.
        if (metadataManager != null) {
            @NotNull
            final List<Table<String, Attribute<String>, List<Attribute<String>>>> t_lTables = metadataManager
                    .getTableDAO().findAllTables();

            if ((t_lTables.size() == 0)) {
                try {
                    metadataManager.eagerlyFetchMetadata();
                } catch (@NotNull final SQLException cannotExtractTableMetadata) {
                    result = true;

                    @Nullable
                    final Log t_Log = UniqueLogFactory.getLog(DatabaseMetaDataCacheReadingHandler.class);

                    if (t_Log != null) {
                        t_Log.warn(CANNOT_EXTRACT_TABLE_METADATA_LITERAL, cannotExtractTableMetadata);
                    }
                } catch (@NotNull final QueryJException otherError) {
                    @Nullable
                    final Log t_Log = UniqueLogFactory.getLog(DatabaseMetaDataCacheReadingHandler.class);

                    if (t_Log != null) {
                        t_Log.warn(CANNOT_EXTRACT_TABLE_METADATA_LITERAL, otherError);
                    }

                    result = true;
                }
            }
        }

        return result;
    }
}