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 *   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
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package org.apache.cayenne.access.jdbc;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

import org.apache.cayenne.access.DataNode;
import org.apache.cayenne.access.OperationObserver;
import org.apache.cayenne.access.jdbc.reader.RowReader;
import org.apache.cayenne.query.Query;
import org.apache.cayenne.query.QueryMetadata;
import org.apache.cayenne.query.SQLAction;

/**
 * A convenience superclass for SQLAction implementations.
 * 
 * @since 1.2
 */
public abstract class BaseSQLAction implements SQLAction {

    protected DataNode dataNode;

    /**
     * @since 4.0
     */
    public BaseSQLAction(DataNode dataNode) {
        this.dataNode = dataNode;
    }

    /**
     * Helper method to process a ResultSet.
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    protected void readResultSet(ResultSet resultSet, RowDescriptor descriptor, Query query, OperationObserver delegate)
            throws SQLException, Exception {

        long t1 = System.currentTimeMillis();

        QueryMetadata metadata = query.getMetaData(dataNode.getEntityResolver());

        RowReader<?> rowReader = dataNode.rowReader(descriptor, metadata);

        JDBCResultIterator resultReader = new JDBCResultIterator(null, resultSet, rowReader);

        LimitResultIterator it = new LimitResultIterator(resultReader, getInMemoryOffset(metadata.getFetchOffset()),
                metadata.getFetchLimit());

        if (!delegate.isIteratedResult()) {
            List resultRows = it.allRows();
            dataNode.getJdbcEventLogger().logSelectCount(resultRows.size(), System.currentTimeMillis() - t1);

            delegate.nextRows(query, resultRows);
        } else {
            try {
                delegate.nextRows(query, it);
            } catch (Exception ex) {
                it.close();
                throw ex;
            }
        }
    }

    /**
     * Returns a value of the offset that will be used to rewind the ResultSet
     * within the SQL action before reading the result rows. The default
     * implementation returns 'queryOffset' argument. If the adapter supports
     * setting offset at the SQL level, this method must be overridden to return
     * zero to suppress manual offset.
     * 
     * @since 3.0
     */
    protected int getInMemoryOffset(int queryOffset) {
        return queryOffset;
    }
}