标签:责任链模式 logs png stc copy manager name 性能 init
假设有这么一个请假系统:员工若想要请3天以内(包括3天的假),只需要直属经理批准就可以了;如果想请3-7天,不仅需要直属经理批准,部门经理需要最终批准;如果请假大于7天,不光要前两个经理批准,也需要总经理最终批准。类似的系统相信大家都遇到过,那么该如何实现呢?首先想到的当然是if…else…,但一旦遇到需求变动,其臃肿的代码和复杂的耦合缺点都显现出来。简单分析下需求,“假条”在三个经理间是单向传递关系,像一条链条一样,因而,我们可以用一条“链”把他们进行有序连接。
构造抽象经理类和各个层级的经理类:
class manager(): successor = None name = ‘‘ def __init__(self, name): self.name = name def setSuccessor(self, successor): self.successor = successor def handleRequest(self, request): pass class lineManager(manager): def handleRequest(self, request): if request.requestType == ‘DaysOff‘ and request.number <= 3: print ‘%s:%s Num:%d Accepted OVER‘ % (self.name, request.requestContent, request.number) else: print ‘%s:%s Num:%d Accepted CONTINUE‘ % (self.name, request.requestContent, request.number) if self.successor != None: self.successor.handleRequest(request) class departmentManager(manager): def handleRequest(self, request): if request.requestType == ‘DaysOff‘ and request.number <= 7: print ‘%s:%s Num:%d Accepted OVER‘ % (self.name, request.requestContent, request.number) else: print ‘%s:%s Num:%d Accepted CONTINUE‘ % (self.name, request.requestContent, request.number) if self.successor != None: self.successor.handleRequest(request) class generalManager(manager): def handleRequest(self, request): if request.requestType == ‘DaysOff‘: print ‘%s:%s Num:%d Accepted OVER‘ % (self.name, request.requestContent, request.number) class request(): requestType = ‘‘ requestContent = ‘‘ number = 0
request类封装了假期请求。在具体的经理类中,可以通过setSuccessor接口来构建“责任链”,并在handleRequest接口中实现逻辑。场景类中实现如下:
if __name__=="__main__": line_manager = lineManager(‘LINE MANAGER‘) department_manager = departmentManager(‘DEPARTMENT MANAGER‘) general_manager = generalManager(‘GENERAL MANAGER‘) line_manager.setSuccessor(department_manager) department_manager.setSuccessor(general_manager) req = request() req.requestType = ‘DaysOff‘ req.requestContent = ‘Ask 1 day off‘ req.number = 1 line_manager.handleRequest(req) req.requestType = ‘DaysOff‘ req.requestContent = ‘Ask 5 days off‘ req.number = 5 line_manager.handleRequest(req) req.requestType = ‘DaysOff‘ req.requestContent = ‘Ask 10 days off‘ req.number = 10 line_manager.handleRequest(req)
打印如下:
LINE MANAGER:Ask 1 day off Num:1 Accepted OVER
LINE MANAGER:Ask 5 days off Num:5 Accepted CONTINUE
DEPARTMENT MANAGER:Ask 5 days off Num:5 Accepted OVER
LINE MANAGER:Ask 10 days off Num:10 Accepted CONTINUE
DEPARTMENT MANAGER:Ask 10 days off Num:10 Accepted CONTINUE
GENERAL MANAGER:Ask 10 days off Num:10 Accepted OVER
责任链模式的定义如下:使多个对象都有机会处理请求,从而避免了请求的发送者和接收者之间的耦合关系。将这些对象连成一条链,并沿着这条链传递该请求,直到有对象处理它为止。
需要说明的是,责任链模式中的应该只有一个处理者,也就是说,本例中的“最终批准”为该对象所谓的“请求处理”。
1、将请求者与处理者分离,请求者并不知道请求是被哪个处理者所处理,易于扩展。
1、若一个请求可能由一个对请求有链式优先级的处理群所处理时,可以考虑责任链模式。除本例外,银行的客户请求处理系统也可以用责任链模式实现(VIP客户和普通用户处理方式当然会有不同)。
1、如果责任链比较长,会有比较大的性能问题;
2、如果责任链比较长,若业务出现问题,比较难定位是哪个处理者的问题。
标签:责任链模式 logs png stc copy manager name 性能 init
原文地址:https://www.cnblogs.com/jokezl/p/10227380.html