Use a web-framework thought experiment to see how Java patterns combine around routing, middleware, request handling, extension, and lifecycle boundaries.
Building even a small web framework quickly shows why patterns rarely appear alone in Java. Request handling, extension points, middleware, serialization, error handling, and resource lifecycle all push the design at once.
A web framework tends to need:
Each pattern answers a different kind of framework pressure.
The common mistake is to design the pattern map first and the request lifecycle second. Good framework design starts from the path of a request:
Only then does it become clear which abstractions need names and which are just plumbing.
Framework code is where patterns are easiest to spot and easiest to misuse. A well-designed framework makes extension and lifecycle explicit. A poorly designed one turns every extension point into a maze of factories, decorators, proxies, and hooks with no clear ownership.
That makes web frameworks a useful teaching surface: the patterns are real, but their costs are visible immediately.