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jfreechart example source code file (JDBCPieDataset.java)

This example jfreechart source code file (JDBCPieDataset.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - jfreechart tags/keywords

a, classnotfoundexception, defaultpiedataset, exception, exception, invalid, jdbc, jdbcpiedataset, jdbcpiedataset, nullpointerexception, resultsetmetadata, sql, sqlexception, sqlexception, string, string

The jfreechart JDBCPieDataset.java source code

/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2008, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * 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.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * -------------------
 * JDBCPieDataset.java
 * -------------------
 * (C) Copyright 2002-2008, by Bryan Scott and Contributors.
 *
 * Original Author:  Bryan Scott; Andy
 * Contributor(s):   David Gilbert (for Object Refinery Limited);
 *                   Thomas Morgner;
 *
 * Changes
 * -------
 * 26-Apr-2002 : Creation based on JdbcXYDataSet, but extending
 *               DefaultPieDataset (BS);
 * 24-Jun-2002 : Removed unnecessary import and local variable (DG);
 * 13-Aug-2002 : Updated Javadoc comments and imports, removed default
 *               constructor (DG);
 * 18-Sep-2002 : Updated to support BIGINT (BS);
 * 21-Jan-2003 : Renamed JdbcPieDataset --> JDBCPieDataset (DG);
 * 03-Feb-2003 : Added Types.DECIMAL (see bug report 677814) (DG);
 * 05-Jun-2003 : Updated to support TIME, optimised executeQuery method (BS);
 * 30-Jul-2003 : Added empty contructor and executeQuery(connection,string)
 *               method (BS);
 * 02-Dec-2003 : Throwing exceptions allows to handle errors, removed default
 *               constructor, as without a connection, a query can never be
 *               executed (TM);
 * 04-Dec-2003 : Added missing Javadocs (DG);
 * ------------- JFREECHART 1.0.x ---------------------------------------------
 * 02-Feb-2007 : Removed author tags all over JFreeChart sources (DG);
 *
 */

package org.jfree.data.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Timestamp;
import java.sql.Types;

import org.jfree.data.general.DefaultPieDataset;
import org.jfree.data.general.PieDataset;

/**
 * A {@link PieDataset} that reads data from a database via JDBC.
 * <P>
 * A query should be supplied that returns data in two columns, the first
 * containing VARCHAR data, and the second containing numerical data.  The
 * data is cached in-memory and can be refreshed at any time.
 */
public class JDBCPieDataset extends DefaultPieDataset {

    /** For serialization. */
    static final long serialVersionUID = -8753216855496746108L;

    /** The database connection. */
    private transient Connection connection;

    /**
     * Creates a new JDBCPieDataset and establishes a new database connection.
     *
     * @param url  the URL of the database connection.
     * @param driverName  the database driver class name.
     * @param user  the database user.
     * @param password  the database users password.
     *
     * @throws ClassNotFoundException if the driver cannot be found.
     * @throws SQLException if there is a problem obtaining a database
     *                      connection.
     */
    public JDBCPieDataset(String url,
                          String driverName,
                          String user,
                          String password)
        throws SQLException, ClassNotFoundException {

        Class.forName(driverName);
        this.connection = DriverManager.getConnection(url, user, password);
    }

    /**
     * Creates a new JDBCPieDataset using a pre-existing database connection.
     * <P>
     * The dataset is initially empty, since no query has been supplied yet.
     *
     * @param con  the database connection.
     */
    public JDBCPieDataset(Connection con) {
        if (con == null) {
            throw new NullPointerException("A connection must be supplied.");
        }
        this.connection = con;
    }


    /**
     * Creates a new JDBCPieDataset using a pre-existing database connection.
     * <P>
     * The dataset is initialised with the supplied query.
     *
     * @param con  the database connection.
     * @param query  the database connection.
     *
     * @throws SQLException if there is a problem executing the query.
     */
    public JDBCPieDataset(Connection con, String query) throws SQLException {
        this(con);
        executeQuery(query);
    }

    /**
     *  ExecuteQuery will attempt execute the query passed to it against the
     *  existing database connection.  If no connection exists then no action
     *  is taken.
     *  The results from the query are extracted and cached locally, thus
     *  applying an upper limit on how many rows can be retrieved successfully.
     *
     * @param  query  the query to be executed.
     *
     * @throws SQLException if there is a problem executing the query.
     */
    public void executeQuery(String query) throws SQLException {
      executeQuery(this.connection, query);
    }

    /**
     *  ExecuteQuery will attempt execute the query passed to it against the
     *  existing database connection.  If no connection exists then no action
     *  is taken.
     *  The results from the query are extracted and cached locally, thus
     *  applying an upper limit on how many rows can be retrieved successfully.
     *
     * @param  query  the query to be executed
     * @param  con  the connection the query is to be executed against
     *
     * @throws SQLException if there is a problem executing the query.
     */
    public void executeQuery(Connection con, String query) throws SQLException {

        Statement statement = null;
        ResultSet resultSet = null;

        try {
            statement = con.createStatement();
            resultSet = statement.executeQuery(query);
            ResultSetMetaData metaData = resultSet.getMetaData();

            int columnCount = metaData.getColumnCount();
            if (columnCount != 2) {
                throw new SQLException(
                    "Invalid sql generated.  PieDataSet requires 2 columns only"
                );
            }

            int columnType = metaData.getColumnType(2);
            double value = Double.NaN;
            while (resultSet.next()) {
                Comparable key = resultSet.getString(1);
                switch (columnType) {
                    case Types.NUMERIC:
                    case Types.REAL:
                    case Types.INTEGER:
                    case Types.DOUBLE:
                    case Types.FLOAT:
                    case Types.DECIMAL:
                    case Types.BIGINT:
                        value = resultSet.getDouble(2);
                        setValue(key, value);
                        break;

                    case Types.DATE:
                    case Types.TIME:
                    case Types.TIMESTAMP:
                        Timestamp date = resultSet.getTimestamp(2);
                        value = date.getTime();
                        setValue(key, value);
                        break;

                    default:
                        System.err.println(
                            "JDBCPieDataset - unknown data type"
                        );
                        break;
                }
            }

            fireDatasetChanged();

        }
        finally {
            if (resultSet != null) {
                try {
                    resultSet.close();
                }
                catch (Exception e) {
                    System.err.println("JDBCPieDataset: swallowing exception.");
                }
            }
            if (statement != null) {
                try {
                    statement.close();
                }
                catch (Exception e) {
                    System.err.println("JDBCPieDataset: swallowing exception.");
                }
            }
        }
    }


    /**
     * Close the database connection
     */
    public void close() {
        try {
            this.connection.close();
        }
        catch (Exception e) {
            System.err.println("JdbcXYDataset: swallowing exception.");
        }
    }
}

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