doc/PoolingDataSourceExample.java

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 * 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.
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import javax.sql.DataSource;
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 setupDataSource
// 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.PoolingDataSource;
import org.apache.commons.dbcp2.PoolableConnectionFactory;
import org.apache.commons.dbcp2.DriverManagerConnectionFactory;

//
// Here's a simple example of how to use the PoolingDataSource.
//

//
// Note that this example is very similar to the PoolingDriver
// example.  In fact, you could use the same pool in both a
// PoolingDriver and a PoolingDataSource
//

//
// To compile this example, you'll want:
//  * commons-pool2-2.3.jar
//  * commons-dbcp2-2.1.jar
// in your classpath.
//
// To run this example, you'll want:
//  * commons-pool2-2.3.jar
//  * commons-dbcp2-2.1.jar
//  * commons-logging-1.2.jar
//  * 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=org.h2.Driver \
//       -classpath commons-pool2-2.3.jar:commons-dbcp2-2.1.jar:commons-logging-1.2.jar:h2-1.3.152.jar:. \
//       PoolingDataSourceExample \
//       "jdbc:h2:~/test" \
//       "SELECT 1"
//
public class PoolingDataSourceExample {

    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("org.h2.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        System.out.println("Done.");

        //
        // Then, we set up the PoolingDataSource.
        // 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 data source.");
        DataSource dataSource = setupDataSource(args[0]);
        System.out.println("Done.");

        //
        // Now, we can use JDBC DataSource as we normally would.
        //
        Connection conn = null;
        Statement stmt = null;
        ResultSet rset = null;

        try {
            System.out.println("Creating connection.");
            conn = dataSource.getConnection();
            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) { }
        }
    }

    public static DataSource setupDataSource(String connectURI) {
        //
        // 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);
        
        // Set the factory's pool property to the owning pool
        poolableConnectionFactory.setPool(connectionPool);

        //
        // Finally, we create the PoolingDriver itself,
        // passing in the object pool we created.
        //
        PoolingDataSource<PoolableConnection> dataSource =
                new PoolingDataSource<>(connectionPool);

        return dataSource;
    }
}