Dynamic Proxy in Python

[Thomas Darimont]

Hallo,

hier mal ein kleines Beispiel wie man sich ganz einfach mit Python dynamic Proxies bauen kann.

Schaut mal hier:

python Code:

#@author: Thomas.Darimont import inspect   class Interface(object):     pass   class IService(Interface):     def businessOperation(self,arguments):         """some business operation"""         pass   class IBubu(Interface):     def someAction(self,arguments):         """xxxx"""         pass   class ServiceImpl(IService,IBubu):     def businessOperation(self,arguments):         print str(arguments)         return str(arguments).upper()         def someAction(self,arguments):         print "xxx"+str(arguments)         return str(arguments)[0]   class IInvocationHandler(Interface):     def invoke(self,proxy,target,methodName,args):         """invoke..."""         pass     class LoggingInvocationHandler(IInvocationHandler):     def invoke(self,proxy,target,methodName,args):         print "before %s" % methodName         result = getattr(target,methodName)(args)         print "after %s" % methodName         return result     class InvokableMethod:     def __init__(self,proxy,invocationTarget,methodName):         self.methodName = methodName         self.proxy = proxy         self.invocationTarget = invocationTarget         def __call__(self,args):         #print "self=%s, args=%s" % (self,args)         #return getattr(self.invocationTarget,self.methodName)(args)         return self.proxy.invocationHandler.invoke(self.proxy,self.invocationTarget,self.methodName,args)           class Proxy(object):         def __init__(self):         pass         @staticmethod     def createProxy(invocationTarget,interfaces,invocationHandler):         #print "interfaces: %s" % interfaces         proxy = Proxy()         proxy.invocationTarget = invocationTarget         proxy.invocationHandler = invocationHandler         proxy.interfaces = interfaces         proxy.interfaceMethodMap = {}         for interface in interfaces:            #print "interfaces to implement %s->%s" % (interface,dir(interface))            for key in dir(interface):                #print "checking: %s" % key                if inspect.ismethod(getattr(interface,key)):                    #print "adding: %s" % key                    if not key in proxy.interfaceMethodMap:                        proxy.interfaceMethodMap[interface] = {key:getattr(interface,key)}                    else:                        proxy.interfaceMethodMap[interface][key]=getattr(interface,key)         return proxy             def __getattr__(self, name):         for interface in self.interfaces:             if name in self.interfaceMethodMap[interface]:                 #print "candidate: %s " % candidate.__name__                 return InvokableMethod(self,self.invocationTarget,self.interfaceMethodMap[interface][name].__name__)                     return None               print ServiceImpl().businessOperation("bubu")   serviceProxy = Proxy.createProxy(ServiceImpl(), [IService(),IBubu()],LoggingInvocationHandler())   print serviceProxy.interfaces   print serviceProxy.businessOperation("test") print "xxxxxxxxxxxxxxxxxxxxx" print serviceProxy.someAction("test")

Ausgabe:

Code:
bubu BUBU [<__main__.IService object at 0x00A87E90>, <__main__.IBubu object at 0x00A87F90>] before businessOperation test after businessOperation TEST xxxxxxxxxxxxxxxxxxxxx before someAction xxxtest after someAction t

Gruß Tom