net.sf.jdmf.data.sources.jdbc.JDBCDataSource.java Source code

Introduction

Here is the source code for net.sf.jdmf.data.sources.jdbc.JDBCDataSource.java

Source

/*
 * JDBCDataSource.java
 *
 * Created: 2006-05-20
 *
 * Java Data Mining Framework (http://jdmf.sourceforge.net)
 * Copyright (C) 2006  Janusz Marchewa
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * $Author: quorthon $
 * $LastChangedRevision: 4 $
 * $LastChangedDate: 2006-07-03 20:10:28 +0200 (pon, 03 lip 2006) $
 */
package net.sf.jdmf.data.sources.jdbc;

import java.math.BigDecimal;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Date;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

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

import net.sf.jdmf.data.sources.DataSource;
import net.sf.jdmf.data.sources.DataSourceException;

/**
 * A JDBC data source. Retrieves attribute names and values using the given
 * queries. Each column in each query result produces another attribute. If many
 * queries return the same column name, the attribute is overwritten each time.
 * To avoid such a situation, use aliases for columns.
 * 
 * Many data mining tools and libraries can retrieve data from only one table or
 * perspective. The ability to merge data from multiple queries is more flexible
 * - there is no need to prepare a special table/perspective before retrieving
 * data. There is one requirement though - each query should return the same
 * number of rows ordered in a way that corresponds to other queries so that
 * the whole instance set remains consistent.
 * 
 * @author quorthon
 */
public class JDBCDataSource implements DataSource {
    private static Log log = LogFactory.getLog(JDBCDataSource.class);

    private String connectionString;
    private String userName;
    private String password;
    private List<String> queries = new ArrayList<String>();

    public JDBCDataSource(Driver driver, String connectionString, String userName, String password, String query) {
        super();

        this.connectionString = connectionString;
        this.userName = userName;
        this.password = password;
        queries.add(query);

        try {
            DriverManager.registerDriver(driver);
        } catch (SQLException e) {
            throw new DataSourceException("Could not register JDBC driver", e);
        }
    }

    public JDBCDataSource(Driver driver, String connectionString, String userName, String password,
            List<String> queries) {
        this(driver, connectionString, userName, password, queries.get(0));

        for (int i = 1; i < queries.size(); ++i) {
            this.queries.add(queries.get(i));
        }
    }

    /**
     * @see net.sf.jdmf.data.sources.DataSource#getAttributes()
     */
    public Map<String, List<Comparable>> getAttributes() {
        Map<String, List<Comparable>> attributes = new LinkedHashMap<String, List<Comparable>>();

        try {
            Connection connection = DriverManager.getConnection(connectionString, userName, password);

            Statement statement = connection.createStatement();

            for (String query : queries) {
                ResultSet resultSet = statement.executeQuery(query);

                ResultSetMetaData metaData = resultSet.getMetaData();
                int columnCount = metaData.getColumnCount();

                for (int i = 1; i <= columnCount; ++i) {
                    String attributeName = metaData.getColumnName(i);
                    List<Comparable> attributeValues = new ArrayList<Comparable>();

                    attributes.put(attributeName, attributeValues);
                }

                while (resultSet.next()) {
                    for (int i = 1; i <= columnCount; ++i) {
                        List<Comparable> attributeValues = attributes.get(metaData.getColumnName(i));

                        attributeValues.add(getValueAsComparable(resultSet.getObject(i)));
                    }
                }

                resultSet.close();
            }

            statement.close();
            connection.close();
        } catch (SQLException e) {
            throw new DataSourceException("Could not retrieve data", e);
        }

        return attributes;
    }

    protected Comparable getValueAsComparable(Object value) {
        Comparable comparable = null;

        if (value instanceof Double || value instanceof Integer || value instanceof BigDecimal) {
            comparable = Double.parseDouble(value.toString());
        } else if (value instanceof String) {
            comparable = value.toString();
        } else if (value instanceof Boolean) {
            comparable = Boolean.parseBoolean(value.toString());
        } else if (value instanceof Date) {
            comparable = new Date(((Date) value).getTime());
        } else {
            log.debug("Unhandled value type: " + value.getClass().getName());
        }

        return comparable;
    }
}