Behavioral Patterns - Chain of Responsibility Pattern Exercise

The Chain of Responsibility Pattern is very useful to avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along with the chain until an object handles it. We will implement a naïve security filter chain using this pattern in our practice exercise. You will certainly enjoy this exercise as it is a great way to get you totally master this pattern.

Reading Materials

1. https://en.wikipedia.org/wiki/Chain-of-responsibility_pattern (15 minutes reading)

Practice Materials

1. Use chain of responsibility pattern to create a naive security filter chain that will check the following responsibilities in order:

1. If any endpoint matches the request

• False - return Not Found

2. If the endpoint has any security rules

• False - return Resource

3. If the request contains any authorization header

• False - return Unauthorized request

4. If the authorization is approved

• False - return Invalid authorization

5. return Resource

Components

• Handler (Interface for handling requests)
• ConcreteHandler (Handle the request it is the responsibility for or forwards it to its successor)
• Client (Initiate the request to a ConcreteHandler object on any part of the chain, in this example, it should start from the the first filter)

Tips

• you may create a Helper class to handle some conditional logic

Solution

Naive Security Chain Example

Questions to discuss

1. What are the common use cases to apply a Chain of Responsibility?
2. What features are there in the application when you see that you should apply the Chain of Responsibility pattern?