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JDBC 数据库连接池

基本概念

先看一张普通连接数据库图：

 

 

　　多个用户操作数据库，向数据库获得链接。数据库创建连接需要较大的资源，而且创建时间长，假设一个网站一天有超 10 万的访问量，则数据库就需要创建更多的连接，这样极大的浪费资源，而且很容易造成数据库服务器内存溢出、拓机。

如何解决此类问题，出现了数据库连接池。如图所示：

 

 

　　连接池相当于一个容器 (集合)，存放数据库连接的容器。当系统初始化好了以后，容器被创建，容器中会申请一些连接对象，当用户来访问数据库时，从容器中获取连接对象，当用户访问完，会将连接对象归还给容器。

详细点就是：

　　使用连接对象之前先创建好规定数量（根据服务器内存的承载能力制定）的连接对象存到放连接池（实现池子的方式一般是用链表结构的集合来实现）中，当应用服务器需要连接对象的时候就从连接池中获取，用完该连接对象时归还连接对象到连接池中。当应用服务器需要连接对象而当前池子中没有连接对象可取时，就让其先等待，如果等待超时还没有回获取到连接对象，就新建一个连接对象给服务器让其使用，用完后销毁该创建的对象。

我的理解

　　就是，当你需要获取数据库连接时，你只需要创建一个连接池对象，定义好 sql 语句，给到连接池，就可以操作数据库。连接池对象就是个工具类，我们需要使用它就创建其对象，写好 SQL 语句就可实现操作数据库。数据库连接池中已经定义好了连接信息，而且我们可以通过修改其配置文件，实现不同数据之间的访问，也可以自定义最大连接量。

数据库连接池的好处

  1. 节约资源（不是关闭连接而是归还）
  2. 用户访问高效（直接获取连接对象，不用创建）

一个最基本的连接池：

public class PersonalConnectionPool {

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 用户名
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> String user;
</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 密码
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> String password;
</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 连接数据库的URL
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> String url;


</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 连接池
 * 规定最大连接数为3
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> LinkedList&lt;Connection&gt;<span style="color: rgba(0, 0, 0, 1)"> pool;

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 从属性文件中加载数据库驱动，初始化连接池
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)">{
    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
        Properties properties </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Properties();
        pool </span>= <span style="color: rgba(0, 0, 255, 1)">new</span> LinkedList&lt;Connection&gt;<span style="color: rgba(0, 0, 0, 1)">();
        Class.forName(</span>"com.mysql.jdbc.Driver"<span style="color: rgba(0, 0, 0, 1)">);
        ClassLoader classLoader </span>= PersonalConnectionPool.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">.getClassLoader();
        InputStream iStream </span>= classLoader.getResourceAsStream("mysqlCongfig.properties"<span style="color: rgba(0, 0, 0, 1)">);
        properties.load(iStream);
        user </span>= properties.getProperty("user"<span style="color: rgba(0, 0, 0, 1)">);
        password </span>= properties.getProperty("password"<span style="color: rgba(0, 0, 0, 1)">);
        url </span>= properties.getProperty("url"<span style="color: rgba(0, 0, 0, 1)">);
        </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">创建三个连接对象（包装类对象）放到池子中</span>
        <span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; 3; i++<span style="color: rgba(0, 0, 0, 1)">) {
            Connection connection </span>=<span style="color: rgba(0, 0, 0, 1)"> DriverManager.getConnection(url, user, password);
            Connection connectionWrapper </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> ConnectionWapper(connection,pool);
            pool.add(connectionWrapper);
        }

    } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (Exception e) {
        </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> TODO Auto-generated catch block</span>



            e.printStackTrace();
}


}


</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * </span><span style="color: rgba(128, 128, 128, 1)">@throws</span><span style="color: rgba(0, 128, 0, 1)"> SQLException 
 * @method 向外提供连接对象
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">public</span> Connection getConnection() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> SQLException {

    Connection connection;
    </span><span style="color: rgba(0, 0, 255, 1)">if</span>(pool.size()&gt;0<span style="color: rgba(0, 0, 0, 1)">)
    {
        connection </span>=<span style="color: rgba(0, 0, 0, 1)"> pool.removeFirst();
    }
    </span><span style="color: rgba(0, 0, 255, 1)">else</span><span style="color: rgba(0, 0, 0, 1)">
    {
        </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">等待超时，返回一个新创建的对象</span>
        connection =<span style="color: rgba(0, 0, 0, 1)"> DriverManager.getConnection(url, user, password);
    }
    System.out.println(</span>"当前池子中有  "+pool.size()+" 个对象"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> connection;
}

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 归还连接对象
 * 直接简化在包装类的close方法中
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span><span style="color: rgba(0, 0, 0, 1)">



}


池子中用了到了一个包装类，包装了通过 DriverManager.getConnection 获取到的 Connection 的实现类对象，该包装也实现了 Connection 接口，重写了案例中需要的方法。该类结构如下：
public class ConnectionWapper implements Connection {


</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * Connection接口的实现类对象的引用
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Connection connection;
</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 存放连接包装对象的池子的引用
 * 
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span> LinkedList&lt;Connection&gt;<span style="color: rgba(0, 0, 0, 1)"> pool;
</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 
 * </span><span style="color: rgba(128, 128, 128, 1)">@param</span><span style="color: rgba(0, 128, 0, 1)"> connection 的实现类对象
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">public</span> ConnectionWapper(Connection connection, LinkedList&lt;Connection&gt;<span style="color: rgba(0, 0, 0, 1)"> pool) {
    </span><span style="color: rgba(0, 0, 255, 1)">super</span><span style="color: rgba(0, 0, 0, 1)">();
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.connection =<span style="color: rgba(0, 0, 0, 1)"> connection;
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.pool =<span style="color: rgba(0, 0, 0, 1)"> pool;
}
@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span> PreparedStatement prepareStatement(String sql) <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> SQLException {
    PreparedStatement prepareStatement </span>=<span style="color: rgba(0, 0, 0, 1)"> connection.prepareStatement(sql);
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> prepareStatement;
}
@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> close() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> SQLException {

    pool.add(</span><span style="color: rgba(0, 0, 255, 1)">this</span><span style="color: rgba(0, 0, 0, 1)">);
    System.out.println(</span>"当前池子中有  "+pool.size()+" 个对象"<span style="color: rgba(0, 0, 0, 1)">);

}

@Override
...



}

基于统一，JAVA 为数据库连接池提供了公共接口，要求所有项目开发的连接池必须实现 DataSource 接口，可一统一用一套接口的方法使用不同开发商的数据库连接池。

常用连接池

dbcp 连接池

  • 封装 dbcp 连接池创建一个数据库工具类
/**
 * (封装 dbcp 连接池来创建数据库工具类)
 * (属性文件为源文件夹 properties 下的 dbcpconfig.properties)
 */
public class DatabaseUtil {

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 数据库连接池（dbcp连接池）对象引用
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> DataSource dbcpPoor;

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 只执行一次
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> {
    Properties properties </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Properties();
    ClassLoader classLoader </span>= DatabaseUtil.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">.getClassLoader();
    InputStream resourceAsStream </span>= classLoader.getResourceAsStream("dbcpconfig.properties"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
        properties.load(resourceAsStream);
        </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">通过直接创建连接池对象并设置参数方法创建连接池对象



//          BasicDataSource basicDataSource = new BasicDataSource();
//          basicDataSource.setUsername(properties.getProperty("username"));
//          basicDataSource.setPassword(properties.getProperty("password"));
//          basicDataSource.setDriverClassName(properties.getProperty("driverClassName"));
//          basicDataSource.setUrl(properties.getProperty("url"));
//
//          dbcpPoor = basicDataSource;
//通过工厂的方法创建连接池对象
dbcpPoor = BasicDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
}
}


</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 获取连接对象
 * </span><span style="color: rgba(128, 128, 128, 1)">@throws</span><span style="color: rgba(0, 128, 0, 1)"> SQLException 
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> Connection getConnection() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> SQLException{
    Connection connection </span>=<span style="color: rgba(0, 0, 0, 1)"> dbcpPoor.getConnection();
    System.out.println(</span>"获取连接对象成功"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> connection;
}

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 关闭资源
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭建立的连接对象，释放资源</span>
    <span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> closeSourceConnection(Connection connection, Statement statement, ResultSet resultSet){

        </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
            </span><span style="color: rgba(0, 0, 255, 1)">if</span> (connection!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
                connection.close();
            }
            </span><span style="color: rgba(0, 0, 255, 1)">if</span> (statement!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
                statement.close();
            }
            </span><span style="color: rgba(0, 0, 255, 1)">if</span> (resultSet!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
                resultSet.close();
            }
        } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (SQLException e) {
            e.printStackTrace();
        }
    }

    </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> DataSource getDbcpPoor() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> dbcpPoor;
}



}

c3p0 连接池

  • 封装 c3p0 连接池创建一个数据库工具类
/**
 * (封装 c3p0 连接池来创建数据库工具类)
 * @author YanoHao
 *
 */
public class DatabaseUtil {
    /**
     * c3p0 连接池对象的引用
     */
    private static DataSource c3p0Poor;
    /**
     * 创建一次
     */
    static {
        //直接创建连接池对象（自动加载配置文件，无需设置参数）
        c3p0Poor = new ComboPooledDataSource();
        //通过工厂的方式创建连接池对象
        //      try {
//          DataSource unpooledDataSource = DataSources.unpooledDataSource();
//          c3p0Poor = DataSources.pooledDataSource(unpooledDataSource);
//      } catch (SQLException e) {
//          // TODO Auto-generated catch block
//          e.printStackTrace();
//      }
    }
    /**
     * 获取连接对象
     * @throws SQLException 
     */
    public static Connection getConnection() throws SQLException{

    Connection connection </span>=<span style="color: rgba(0, 0, 0, 1)"> c3p0Poor.getConnection();
    System.out.println(</span>"获取连接对象成功"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> connection;
}

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 关闭资源
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭建立的连接对象，释放资源</span>
    <span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> closeSourceConnection(Connection connection, Statement statement, ResultSet resultSet){

        </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
            </span><span style="color: rgba(0, 0, 255, 1)">if</span> (connection!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
                connection.close();
            }
            </span><span style="color: rgba(0, 0, 255, 1)">if</span> (statement!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
                statement.close();
            }
            </span><span style="color: rgba(0, 0, 255, 1)">if</span> (resultSet!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
                resultSet.close();
            }
        } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (SQLException e) {
            e.printStackTrace();
        }
    }

    </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> DataSource getC3p0Poor() {
        </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> c3p0Poor;
    }



}

druid 连接池

  • 封装 druid 连接池创建一个数据库工具类
/*
 * 封装 druid 连接池创建工具类
 */
public class DatabaseUtil {

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 数据库连接池（druid连接池）对象引用
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> DataSource druidPool;

</span><span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> {
    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
        Properties properties </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Properties();
        ClassLoader classLoader </span>= DatabaseUtil.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">.getClassLoader();
        InputStream resourceAsStream </span>= classLoader.getResourceAsStream("druidconfig.properties"<span style="color: rgba(0, 0, 0, 1)">);
        properties.load(resourceAsStream);
        </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">通过直接创建连接池对象的方式创建连接池对象



//          DruidDataSource druidDataSource = new DruidDataSource();
//          druidDataSource.setUsername(properties.getProperty("username"));
//          druidDataSource.setPassword(properties.getProperty("password"));
//          druidDataSource.setUrl(properties.getProperty("url"));
//          druidDataSource.setDriverClassName(properties.getProperty("driverClassName"));
//          druidPool = druidDataSource;
//通过工厂的方式创建连接池对象
druidPool = DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
}
}


</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> Connection getConnection() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> SQLException{

    Connection connection </span>=<span style="color: rgba(0, 0, 0, 1)"> druidPool.getConnection();
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> connection;
}

</span><span style="color: rgba(0, 128, 0, 1)">/**</span><span style="color: rgba(0, 128, 0, 1)">
 * 
 * 关闭建立的连接对象，释放资源
 </span><span style="color: rgba(0, 128, 0, 1)">*/</span>
<span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> closeSourceConnection(Connection connection, Statement statement, ResultSet resultSet){

    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
        </span><span style="color: rgba(0, 0, 255, 1)">if</span> (connection!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
            connection.close();
        }
        </span><span style="color: rgba(0, 0, 255, 1)">if</span> (statement!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
            statement.close();
        }
        </span><span style="color: rgba(0, 0, 255, 1)">if</span> (resultSet!=<span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
            resultSet.close();
        }
    } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (SQLException e) {
        e.printStackTrace();
    }
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> DataSource getDruidPool() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> druidPool;
}



}