Building an Order Processing Pipeline in Java Using Chain of Responsibility Pattern

The Chain of Responsibility is a behavioral design pattern from the Gang of Four that routes a request through a sequence of handlers, each deciding whether to process or pass it along. A common problem in e-commerce systems is that order processing logic — covering stock validation, payment, shipping, and persistence — gets crammed into a single bloated method, reducing maintainability. The pattern solves this by splitting the workflow into independent handlers, each responsible for exactly one step, similar to stations on a production line. In a typical order pipeline, if any handler fails — such as a payment rejection — the chain stops immediately and prevents subsequent steps from executing. This approach improves code cohesion, simplifies reordering of steps, and makes individual handlers reusable in isolation.