Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ import java.sql.DriverManager; import java.sql.Connection; import java.sql.Statement; import java.sql.ResultSet; import java.sql.SQLException; // // Here are the dbcp-specific classes. // Note that they are only used in the setupDriver // method. In normal use, your classes interact // only with the standard JDBC API // import org.apache.commons.pool2.ObjectPool; import org.apache.commons.pool2.impl.GenericObjectPool; import org.apache.commons.dbcp2.ConnectionFactory; import org.apache.commons.dbcp2.PoolableConnection; import org.apache.commons.dbcp2.PoolingDriver; import org.apache.commons.dbcp2.PoolableConnectionFactory; import org.apache.commons.dbcp2.DriverManagerConnectionFactory; // // Here's a simple example of how to use the PoolingDriver. // // // To compile this example, you'll want: // * commons-pool-1.5.6.jar // * commons-dbcp-1.3.jar (JDK 1.4-1.5) or commons-dbcp-1.4 (JDK 1.6+) // in your classpath. // // To run this example, you'll want: // * commons-collections.jar // * commons-pool-1.5.6.jar // * commons-dbcp-1.3.jar (JDK 1.4-1.5) or commons-dbcp-1.4 (JDK 1.6+) // * the classes for your (underlying) JDBC driver // in your classpath. // // Invoke the class using two arguments: // * the connect string for your underlying JDBC driver // * the query you'd like to execute // You'll also want to ensure your underlying JDBC driver // is registered. You can use the "jdbc.drivers" // property to do this. // // For example: // java -Djdbc.drivers=oracle.jdbc.driver.OracleDriver \ // -classpath commons-pool-1.5.6.jar:commons-dbcp-1.4.jar:oracle-jdbc.jar:. \ // PoolingDriverExample \ // "jdbc:oracle:thin:scott/tiger@myhost:1521:mysid" \ // "SELECT * FROM DUAL" // public class PoolingDriverExample { public static void main(String[] args) { // // First we load the underlying JDBC driver. // You need this if you don't use the jdbc.drivers // system property. // System.out.println("Loading underlying JDBC driver."); try { Class.forName("oracle.jdbc.driver.OracleDriver"); } catch (ClassNotFoundException e) { e.printStackTrace(); } System.out.println("Done."); // // Then we set up and register the PoolingDriver. // Normally this would be handled auto-magically by // an external configuration, but in this example we'll // do it manually. // System.out.println("Setting up driver."); try { setupDriver(args[0]); } catch (Exception e) { e.printStackTrace(); } System.out.println("Done."); // // Now, we can use JDBC as we normally would. // Using the connect string // jdbc:apache:commons:dbcp:example // The general form being: // jdbc:apache:commons:dbcp:<name-of-pool> // Connection conn = null; Statement stmt = null; ResultSet rset = null; try { System.out.println("Creating connection."); conn = DriverManager.getConnection("jdbc:apache:commons:dbcp:example"); System.out.println("Creating statement."); stmt = conn.createStatement(); System.out.println("Executing statement."); rset = stmt.executeQuery(args[1]); System.out.println("Results:"); int numcols = rset.getMetaData().getColumnCount(); while (rset.next()) { for (int i = 1; i <= numcols; i++) { System.out.print("\t" + rset.getString(i)); } System.out.println(""); } } catch (SQLException e) { e.printStackTrace(); } finally { try { if (rset != null) rset.close(); } catch (Exception e) { } try { if (stmt != null) stmt.close(); } catch (Exception e) { } try { if (conn != null) conn.close(); } catch (Exception e) { } } // Display some pool statistics try { printDriverStats(); } catch (Exception e) { e.printStackTrace(); } // closes the pool try { shutdownDriver(); } catch (Exception e) { e.printStackTrace(); } } public static void setupDriver(String connectURI) throws Exception { // // First, we'll create a ConnectionFactory that the // pool will use to create Connections. // We'll use the DriverManagerConnectionFactory, // using the connect string passed in the command line // arguments. // ConnectionFactory connectionFactory = new DriverManagerConnectionFactory(connectURI, null); // // Next, we'll create the PoolableConnectionFactory, which wraps // the "real" Connections created by the ConnectionFactory with // the classes that implement the pooling functionality. // PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory, null); // // Now we'll need a ObjectPool that serves as the // actual pool of connections. // // We'll use a GenericObjectPool instance, although // any ObjectPool implementation will suffice. // ObjectPool<PoolableConnection> connectionPool = new GenericObjectPool<>(poolableConnectionFactory); // // Finally, we create the PoolingDriver itself... // Class.forName("org.apache.commons.dbcp2.PoolingDriver"); PoolingDriver driver = (PoolingDriver) DriverManager.getDriver("jdbc:apache:commons:dbcp:"); // // ...and register our pool with it. // driver.registerPool("example", connectionPool); // // Now we can just use the connect string "jdbc:apache:commons:dbcp:example" // to access our pool of Connections. // } public static void printDriverStats() throws Exception { PoolingDriver driver = (PoolingDriver) DriverManager.getDriver("jdbc:apache:commons:dbcp:"); ObjectPool<? extends Connection> connectionPool = driver.getConnectionPool("example"); System.out.println("NumActive: " + connectionPool.getNumActive()); System.out.println("NumIdle: " + connectionPool.getNumIdle()); } public static void shutdownDriver() throws Exception { PoolingDriver driver = (PoolingDriver) DriverManager.getDriver("jdbc:apache:commons:dbcp:"); driver.closePool("example"); } }