Java 如何从连接池tomcat 8获取连接

我正在学习如何使用ServletAPI，并尝试开发我的第一个web应用程序。我的JDBC连接有问题。我知道如何连接到数据库，但我想从连接池获得连接。我不明白我怎么能用它。您能给我一些建议或链接到示例应用程序，看看它是如何工作的吗

GenericObjectPool类可用于创建任意对象池。您可以如下所示创建池

public DataSource setUpPool() throws Exception {

Class.forName(JDBC_DRIVER);
// Creates an Instance of GenericObjectPool That Holds Our Pool of Connections Object!
        gPool = new GenericObjectPool();
        gPool.setMaxActive(5);
// Creates a ConnectionFactory Object Which Will Be Use by the Pool to Create the Connection Object!

ConnectionFactory cf = new DriverManagerConnectionFactory(JDBC_DB_URL, JDBC_USER, JDBC_PASS);

// Creates a PoolableConnectionFactory That Will Wraps the Connection Object Created by the ConnectionFactory to Add Object Pooling Functionality!


PoolableConnectionFactory pcf = new PoolableConnectionFactory(cf, gPool, null, null, false, true);

return new PoolingDataSource(gPool);
}

使用上述方法从池中获取连接：

ConnectionPool jdbcObj = new ConnectionPool();
Connection connObj = null;
DataSource dataSource = jdbcObj.setUpPool();
connObj = dataSource.getConnection();