Is the managed bean singleton?

[Ivan Lou]

I'm beginner of learning jsf. I want to know whether the managed bean is singleton

[Tim Holloway]

Yes and no. It depends on how "single" you want it.

An application-scope managed bean is truly single. Only one of them per copy of the deployed webapp per server VM.

A session-scope managed bean is singleton on a per-user basis, but with multiple users, each user gets a unique and separate bean instance.

A request-scope bean is singleton on a per-request basis, but there can be lots of requests.

The "single"-ness of managed beans is determined by the fact that each bean ID in faces-config must be unique, so only one bean with that ID may exist in the context of its defined scope.

Only application scope is really singleton, the rest, like I said are unique, but only withing their contexts.

[Ivan Lou]

Tim Holloway wrote:Yes and no. It depends on how "single" you want it.

An application-scope managed bean is truly single. Only one of them per copy of the deployed webapp per server VM.

A session-scope managed bean is singleton on a per-user basis, but with multiple users, each user gets a unique and separate bean instance.

A request-scope bean is singleton on a per-request basis, but there can be lots of requests.

The "single"-ness of managed beans is determined by the fact that each bean ID in faces-config must be unique, so only one bean with that ID may exist in the context of its defined scope.

Only application scope is really singleton, the rest, like I said are unique, but only withing their contexts.

Thank you, Tim Holloway.