public class MyDataSource { 
  private LinkedList<Connection> connectionPool = new LinkedList<Connection>(); 
 
  public MyDataSource() { 
    for (int i = 0; i < 10; i++) { 
      connectionPool.add(new MyConnection(creatConnection(),this)); 
    } 
  } 
  private Connection creatConnection() { 
    try { 
      return DriverManager.getConnection( 
          "jdbc:mysql://localhost:3306/test", "root", "root"); 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      throw new ExceptionInInitializerError(); 
    } 
  } 
   
  public Connection getConnection(){ 
    System.out.println(connectionPool.size()); 
    return connectionPool.removeFirst(); 
  } 
   
  public void freeConnection(Connection conn){ 
    System.out.println("DataSource Close Connection"); 
    connectionPool.addLast(conn); 
  } 
} 
 

public class MyConnection implements Connection{ 
  private Connection connection; 
  private MyDataSource datasource; 
  public Connection getConnection() { 
    return connection; 
  } 
 
  public void setConnection(Connection connection) { 
    this.connection = connection; 
  } 
 
  public MyConnection(Connection realconnection,MyDataSource datasource){ 
    this.connection=realconnection; 
    this.datasource=datasource; 
  } 
   
  @Override 
  public void close() throws SQLException { 
    // TODO Auto-generated method stub 
    System.out.println("MyConnection Close"); 
    datasource.freeConnection(this); 
  } 
  ... 
} 

public class MyDataSource { 
  private LinkedList<Connection> connectionPool = new LinkedList<Connection>(); 
 
  public MyDataSource() { 
    for (int i = 0; i < 10; i++) { 
      connectionPool.add(GetProxy(creatConnection())); 
    } 
  } 
 
  private Connection GetProxy(final Connection connection) { 
    // TODO Auto-generated method stub 
    return (Connection)Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[]{Connection.class}, new InvocationHandler(){ 
      @Override 
      public Object invoke(Object proxy, Method method, Object[] args) 
          throws Throwable { 
        // TODO Auto-generated method stub 
        Object value; 
        if(method.getName().equalsIgnoreCase("close")){ 
          connectionPool.addLast((Connection)proxy); 
          System.out.println(connectionPool.size()); 
          return null; 
        }else{ 
          value=method.invoke(connection, args); 
        } 
        System.out.println(connectionPool.size()); 
        return value; 
      } 
       
    }); 
     
  } 
 
  private Connection creatConnection() { 
    try { 
      return DriverManager.getConnection( 
          "jdbc:mysql://localhost:3306/test", "root", "root"); 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      throw new ExceptionInInitializerError(); 
    } 
  } 
   
  public Connection getConnection(){ 
    System.out.println(connectionPool.size()); 
    return connectionPool.removeFirst(); 
  } 
   
  public void freeConnection(Connection conn){ 
    System.out.println("DataSource Close Connection"); 
    connectionPool.addLast(conn); 
  } 
}