databasedatarow.java

著名的开源仿真软件yale

/*
 *  YALE - Yet Another Learning Environment
 *  Copyright (C) 2002, 2003
 *      Simon Fischer, Ralf Klinkenberg, Ingo Mierswa, 
 *          Katharina Morik, Oliver Ritthoff
 *      Artificial Intelligence Unit
 *      Computer Science Department
 *      University of Dortmund
 *      44221 Dortmund,  Germany
 *  email: [e-mail]
 *  web:   http://yale.cs.uni-dortmund.de/
 *
 *  This program 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 (at your option) any later version. 
 *
 *  This program 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 program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 *  USA.
 */
package edu.udo.cs.yale.example;

import edu.udo.cs.yale.tools.DatabaseHandler;

import java.sql.ResultSet;
import java.sql.SQLException;

/** Reads datarows from a data base.
 *
 *  @version $Id: DatabaseDataRow.java,v 2.5 2003/06/12 14:43:33 fischer Exp $
 */
public class DatabaseDataRow implements DataRow {

    private ResultSet resultSet;
    private int row;

    public DatabaseDataRow(ResultSet resultSet) throws SQLException {
	this.resultSet = resultSet;
	this.row       = resultSet.getRow();
    }

    private void ensureRowCorrect() throws SQLException {
	if (row != resultSet.getRow()) {
	    throw new RuntimeException("ResultSet was modified!");
	}
    }

    public double get(Attribute attribute) {
	Object dbData = null;
	try {
	    ensureRowCorrect();
	    return readColumn(resultSet, attribute);
	} catch (SQLException e) {
	    throw new RuntimeException("Cannot read data: "+e);
	}
    }

    public void set(Attribute attribute, double value) {
	try {
	    ensureRowCorrect();
	    String name = DatabaseHandler.getDatabaseName(attribute);
	    if (Double.isNaN(value)) {
		resultSet.updateNull(name);
	    } else {
		if (attribute.isNominal()) {
		    resultSet.updateString(name, attribute.mapIndex((int)value));
		} else {
		    resultSet.updateDouble(name, value);
		}
	    }
	    resultSet.updateRow();
	} catch (SQLException e) {
	    throw new RuntimeException("Cannot update data: "+e, e);
	}
    }

    public void ensureNumberOfColumns(int numberOfColumns) {}

    public static double readColumn(ResultSet resultSet, Attribute attribute) throws SQLException {
	String name = DatabaseHandler.getDatabaseName(attribute);
	if (attribute.isNominal()) {
	    String dbString = resultSet.getString(name);
	    if (dbString == null) return Double.NaN;
	    return attribute.mapString(dbString);
	} else {
	    double value = resultSet.getDouble(name);
	    if (resultSet.wasNull()) {
		return Double.NaN;
	    } else {
		return value;
	    }
	}
    }

}