public class DBPool
{
    private static DataSource    pool;
    static
    {
        Context env = null;
        try
        {
            env = (Context) new InitialContext().lookup("java:comp/env");
            pool = (DataSource) env.lookup("jdbc/DBpool");
            if(pool == null)
                System.err.println("'DBpool' is an unknown DataSource");
        }
        catch (NamingException ne)
        {
            ne.printStackTrace();
        }
    }

    public static DataSource getPool()
    {
        return pool;
    }
}

public byte[] getStaticEntiy(String pmname, int scalesize, float x, float y)
    {
        byte[] bContent = null;
        try
        {
            conn = DBPool.getPool().getConnection();    //获取连接池中的链接

            bContent = scaledao.getStaticEntiy(pmname, scalesize, x, y, conn);    //这是一般的从数据库读取流数据的方法    
        }
        catch (SQLException e)
        {
            e.printStackTrace();
        }
        finally
        {
            if(conn!=null){
                try
                {
                    conn.close();                   //释放链接
                }
                catch (SQLException e)
                {
                    e.printStackTrace();
                }
            }
        }
        
        return bContent;
    }