com.kennberg.appenginecpeg.SQLManager.java Source code

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/**
 * Google App Engine Connection Pool Example
 *
 * Copyright 2015 Alex Kennberg (https://github.com/kennberg/appengine-java-connection-pool)
 *
 * Licensed 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.
 */
package com.kennberg.appenginecpeg;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.logging.Logger;

import org.apache.commons.dbcp.BasicDataSource;

public class SQLManager {
    private static final Logger LOG = Logger.getLogger(SQLManager.class.getName());

    private static final int MIN_CONNECTION_POOL_SIZE = 2;
    private static final int MAX_CONNECTION_POOL_SIZE = 5;

    // Connection pool will start throwing errors when connections take more than
    // this amount to execute and there are no available spots for new connections.
    private static final long MAX_CONNECTION_WAIT_MS = 30000L;

    // This datasource lives as long as the instance lives.
    private static BasicDataSource dataSource = null;
    private static final Object dataSourceLock = new Object();

    private String driverClassName;
    private boolean useConnectionPool;
    private String address;
    private String username;
    private String password;

    public SQLManager(final String driverClassName, final boolean useConnectionPool, final String address,
            final String username, final String password) {
        this.driverClassName = driverClassName;
        this.useConnectionPool = useConnectionPool;
        this.address = address;
        this.username = username;
        this.password = password;

        try {
            Class.forName(driverClassName);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(
                    "Cannot find the SQL driver in the classpath." + " driver=" + driverClassName, e);
        }
    }

    public Connection getConnection() throws SQLException {
        if (!useConnectionPool) {
            if (username == null) {
                return DriverManager.getConnection(address);
            } else {
                return DriverManager.getConnection(address, username, password);
            }
        }

        synchronized (dataSourceLock) {
            if (dataSource == null) {
                dataSource = new BasicDataSource();
                dataSource.setDriverClassName(driverClassName);
                dataSource.setUrl(address);
                if (username != null) {
                    dataSource.setUsername(username);
                    dataSource.setPassword(password);
                }
                dataSource.setInitialSize(MIN_CONNECTION_POOL_SIZE);
                dataSource.setMaxActive(MAX_CONNECTION_POOL_SIZE);
                dataSource.setMaxIdle(MAX_CONNECTION_POOL_SIZE);
                dataSource.setMaxWait(MAX_CONNECTION_WAIT_MS);

                dataSource.setTestOnBorrow(true);
                dataSource.setValidationQuery("SELECT 1");

                // From BasicDataSourceFactory.java, DBCP-215
                // Trick to make sure that initialSize connections are created
                if (dataSource.getInitialSize() > 0) {
                    dataSource.getLogWriter();
                }
            }

            return dataSource.getConnection();
        } // synchronized dataSourceLock
    }
}