django-sample03.py

proxies = {}
 
class _ConnectionWrapper(object):
    """
    用来包装Connection的类
    """
    def __init__(self,conn):
        self.conn=conn
 
    def close(self):
        """
        屏蔽掉关闭连接的行为
        """
        pass
 
    def __getattr__(self,key):
        """
        把其他属性都原封不动的代理出去
        """
        return getattr(self.conn, key)
 
class _DbWrapper():
    """
    代理MySQLdb模块的对象
    """
    def __init__(self,module):
        self.connection=None  #HOLD住的长连接
        self.db=module            #原始的MySQLdb模块
 
    def __getattr__(self, key):
        """
        代理除connect外的所有属性
        """
        return getattr(self.db, key)
 
    def connect(self,*argv,**kwargv):
        if not self.connection:
            self.connection=self.db.connect(*argv,**kwargv)
        return _ConnectionWrapper(self.connection)
 
def manage(module):
    try:
        return proxies[module]
    except KeyError:
        return proxies.setdefault(module,_DbWrapper(module))