org.mule.module.db.internal.result.resultset.ResultSetIterator.java Source code

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Here is the source code for org.mule.module.db.internal.result.resultset.ResultSetIterator.java

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/*
 * Copyright (c) MuleSoft, Inc.  All rights reserved.  http://www.mulesoft.com
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */

package org.mule.module.db.internal.result.resultset;

import org.mule.api.Closeable;
import org.mule.api.MuleException;
import org.mule.module.db.internal.domain.connection.DbConnection;
import org.mule.module.db.internal.result.row.RowHandler;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Iterates a {@link ResultSet} to provide rows streaming
 */
public class ResultSetIterator implements Iterator<Map<String, Object>>, Closeable {

    protected static final Log logger = LogFactory.getLog(ResultSetIterator.class);

    private final ResultSet resultSet;
    private final RowHandler rowHandler;
    private final StreamingResultSetCloser streamingResultSetCloser;
    private DbConnection connection;
    private Boolean cachedNext = null;

    public ResultSetIterator(DbConnection connection, ResultSet resultSet, RowHandler rowHandler,
            StreamingResultSetCloser streamingResultSetCloser) {
        if (connection == null) {
            throw new NullPointerException();
        }
        this.resultSet = resultSet;
        this.rowHandler = rowHandler;
        this.streamingResultSetCloser = streamingResultSetCloser;
        this.connection = connection;
    }

    @Override
    public boolean hasNext() {
        boolean result = false;
        if (cachedNext == null) {
            try {
                cachedNext = resultSet.next();
                result = cachedNext;
            } catch (SQLException e) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Unable to determine if there are more records", e);
                }
            }

            if (!result) {
                try {
                    close();
                } catch (MuleException e) {
                    if (logger.isDebugEnabled()) {
                        logger.debug("Error closing resultset", e);
                    }
                }
            }
        } else {
            result = cachedNext;
        }

        return result;
    }

    @Override
    public Map<String, Object> next() {
        try {
            if (cachedNext == null) {
                resultSet.next();
            } else {
                cachedNext = null;
            }

            return rowHandler.process(resultSet);
        } catch (SQLException e) {
            logger.warn("Unable to obtain next row", e);

            throw new NoSuchElementException();
        }
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }

    @Override
    public void close() throws MuleException {
        if (logger.isDebugEnabled()) {
            logger.debug("Closing resultSet");
        }

        streamingResultSetCloser.close(connection, resultSet);
    }
}