net.sf.morph2.reflect.support.ResultSetIterator.java Source code

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Here is the source code for net.sf.morph2.reflect.support.ResultSetIterator.java

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/*
 * 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 net.sf.morph2.reflect.support;

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

import net.sf.morph2.MorphException;

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

/**
 * An iterator over a ResultSet.  SQLExceptions are wrapped in MorphExceptions.
 *
 * @author Matt Sgarlata
 * @since Dec 20, 2004
 */
public class ResultSetIterator implements Iterator {

    private static final Log log = LogFactory.getLog(ResultSetIterator.class);
    private static final String NO_MORE = "There are no more rows in the ResultSet";

    private ResultSet resultSet;
    private boolean hasNext;
    // set to true if the current row has been successfully sent to the user
    private boolean hasReturnedRow;

    /**
     * Create a new ResultSetIterator instance.
     * @param resultSet
     */
    public ResultSetIterator(ResultSet resultSet) {
        this.resultSet = resultSet;
        // initialize to true, since when we start the result set begins before
        // the first row.  we don't actually need to return the row before the
        // first row, so we can consider it as having been already returned
        this.hasReturnedRow = true;
    }

    /**
     * {@inheritDoc}
     */
    public boolean hasNext() {
        if (hasReturnedRow) {
            advanceToNextRow();
            hasReturnedRow = false;
        }
        return hasNext;
    }

    /**
     * {@inheritDoc}
     */
    public Object next() {
        if (hasNext()) {
            hasReturnedRow = true;
            return resultSet;
        }
        throw new NoSuchElementException(NO_MORE);
    }

    /**
     * Advance to next row.
     * @throws MorphException
     */
    protected void advanceToNextRow() throws MorphException {
        try {
            hasNext = resultSet.next();
        } catch (SQLException e) {
            handleResultSetNextException(e);
        }
    }

    /**
     * Handle ResultSet next exception.
     * @param e
     * @throws MorphException
     */
    protected void handleResultSetNextException(SQLException e) throws MorphException {
        if (log.isErrorEnabled()) {
            log.error("Error moving to next row in resultSet", e);
        }
        throw new MorphException("Error moving to next row in resultSet", e);
    }

    /**
     * {@inheritDoc}
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }
}