Java tutorial
/* =========================================================== * 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.chart.event.DatasetChangeInfo; import org.jfree.data.pie.DefaultPieDataset; import org.jfree.data.pie.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(new DatasetChangeInfo()); //TODO: fill in real change info } 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."); } } }