abount the singleton beans of spring

I wish this help you take a look at Method Injection

To fix the issue you can do Your default position should be to use singleton controllers which are thread-safe. This partly for performance reasons, as you say, and partly for reasons of good design - a large mass of stateful, request-scoped beans is a mess.
Using request-scoped controllers (or other request-scoped beans) is a specialised requirement which you should only use when you have good reason to do so, i.e. you have beans whose state must be private to the lifecycle of that particular request.

seems to work fine
If I scope Dependency as prototype, I will always get a new instance, breaching constraint 2