python实现责任链模式

把多个处理方法串成一个list。下一个list的节点是上一个list的属性。

每个节点都有判断是否能处理当前数据的方法。能处理，则直接处理，不能处理则调用下一个节点（也就是当前节点的属性）来进行处理。

Python 实现责任链模式，以request 的请求处理为例：

1、RequestHandler 类：

基础的请求处理器类，定义了处理请求的接口和责任链的基本逻辑。

2、子类 GetRequestHandler, PostRequestHandler, PutRequestHandler, DeleteRequestHandler：

每个子类实现了 can_handle 方法和 handle 方法，根据请求的方法（GET, POST, PUT, DELETE）判断是否能够处理该请求，并实现具体的请求处理逻辑。

3、Usage 部分：

创建了一个示例的请求对象 Request，包含请求的方法 (method) 和 URL (url)。
创建了四个请求处理器，并按照顺序构建了责任链：GET -> POST -> PUT -> DELETE。
调用 get_handler.handle_request(authentication_info_obj) 发起请求处理，结果会根据请求方法逐级传递到能够处理该请求的处理器，并返回处理结果。

python 复制代码

class RequestHandler:
    def __init__(self, successor=None):
        self.successor = successor
    
    def handle_request(self, request):
        if not self.successor:
            raise NotImplementedError("A successor must be defined.")
        
        if self.can_handle(request):
            return self.handle(request)
        else:
            return self.successor.handle_request(request)
    
    def can_handle(self, request):
        raise NotImplementedError("Subclasses should implement this method.")
    
    def handle(self, request):
        raise NotImplementedError("Subclasses should implement this method.")


class GetRequestHandler(RequestHandler):
    def can_handle(self, request):
        return request['method'] == 'GET'  # Check if the method is GET
    
    def handle(self, request):
        # Handle GET request logic
        return f"Handling GET request for {request['url']}"


class PostRequestHandler(RequestHandler):
    def can_handle(self, request):
        return request['method'] == 'POST'  # Check if the method is POST
    
    def handle(self, request):
        # Handle POST request logic
        return f"Handling POST request for {request['url']}"


class PutRequestHandler(RequestHandler):
    def can_handle(self, request):
        return request['method'] == 'PUT'  # Check if the method is PUT
    
    def handle(self, request):
        # Handle PUT request logic
        return f"Handling PUT request for {request['url']}"


class DeleteRequestHandler(RequestHandler):
    def can_handle(self, request):
        return request['method'] == 'DELETE'  # Check if the method is DELETE
    
    def handle(self, request):
        # Handle DELETE request logic
        return f"Handling DELETE request for {request['url']}"


# Usage
if __name__ == "__main__":
    request_obj = {'method': 'GET', 'url': 'https://example.com'}
    
    # Create handlers
    delete_handler = DeleteRequestHandler()
    put_handler = PutRequestHandler(delete_handler)
    post_handler = PostRequestHandler(put_handler)
    get_handler = GetRequestHandler(post_handler)
    
    # Example usage
    result = get_handler.handle_request(request_obj)
    print(result)